Author Topic: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371  (Read 3798 times)

0 Members and 1 Guest are viewing this topic.

Online shakalnokturn

  • Super Contributor
  • ***
  • Posts: 1436
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #25 on: April 15, 2021, 08:35:56 pm »
Nice gift that Quad... I see there's a fistfull of blue Philips and plastic ERO? electrolytics in there. Another topic on the way.
Depending on the size of the Sony monitor I'd hold on to it. Some HP TE used Trinitron CRT's that are usually way overtime.
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #26 on: April 15, 2021, 08:36:17 pm »
OH !

Just realized, at the back of that QUAD preamp unit, it reads "Made in Huntingdon, England " ?!

Wow, now that brings some memories !!!

Used to live there ! 

Moved to the UK for 3 years to do my BEng degree in electronics, between 1998 and 2001.

Uni was located in Hatfield, Herts, north London, but for my "Sandwich" / placement year, I found a position in a small company in Cambridgeshire, in a little village by the name of Saint-Ives, which is right next to Huntingdon ! My boss at the electronics R&D dept. lived in Huntingdon.. little did I know that QUAD was located there as well !  :-//  Might have paid a visit had I known.

Company was called Webtec, still in business today. Actually I still have the business card of my R&D boss in my Wallet, 20+ years later ! LOL

https://en.webtec.com/

Even found a couple pictures of the prototype I was developing... feels like yesterday but was 21 years ago ?! Time flies  :(


Runs on this back then fancy PIC thing, a state of the art  :-DD  FLASH micro-controller with in circuit programming, and built-in EEPROM ! WOW !!! Sounded like a revolution compared to the Intel 8051 I cut my teeth on at school just a couple years earlier !

I remember it was a PIC 16F876 or 877 can't remember. It was so atrocious to program that I missed the old 8051 so much.
At the very beginning of my placement, before I was given this then state of the art PIC, I dabbled briefly with a 17CXX IIRC, an antic PIC with a glass window to erase its internal EPROM ! Would spend most of my day waiting for the small UV eraser on my desk to clear the bloody thing so I could change a line of code and give it a try ! What a pain that was !   |O

« Last Edit: April 15, 2021, 09:47:17 pm by Vince »
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #27 on: April 15, 2021, 09:13:28 pm »
Nice gift that Quad... I see there's a fistfull of blue Philips and plastic ERO? electrolytics in there. 

Only one blue Philips that I can see. As for the ERO ones.... you have not yet taught me about them... which ones are they ?
The small radial ones, in a perfectly cylindrical plastic body, either black or orange ? Lot of them indeed. Just noticed one of them let the magic smoke escape !!!  A black one, located from what I guess must be the power supply board. Right next to the big blue Philips.


Quote
Another topic on the way. Depending on the size of the Sony monitor I'd hold on to it. Some HP TE used Trinitron CRT's that are usually way overtime.

Oh no, I had only a brief look at it on his smartphone, he took a crappy pic. From that brief look, it looked to me like a tiny minuscule portable monitor... like a portable TV or something, but I am sure he said it was a "monitor"... looked light brown, either that or extremely yellowed beige... looked anti, crusty, an extreme piece of junk no-one on earth would want near him. But he said he would bring me all the stuff this week-end, so I will be able to know for sure, and report back of course !  ;D

« Last Edit: April 15, 2021, 10:18:26 pm by Vince »
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #28 on: April 15, 2021, 09:39:58 pm »
Your CD371 has the makings of a nice little project.

Yeah you and Shakal had me grow very fond of this little bugger, I love it now, want to fix it and mod it and enjoy it.. not going to sell it, no no no...


Quote
I still think you could make up a replacement display using an MM5450, and a bit of stripboard - as an interim step to your final metal cased monster! Enough to be useable anyway, and you only really need to connect up two digits (only 15 wires)... or none at all if you just want music out of it!

Hmmmm....... either I am weak person and/or you have a lot convincing power but.... OK let's do something real quick... thinking of it, it really doesn't look that complicated/long to do. Will order one or two of these chips and some prototyping board... but just a few wires, not ugly mess... just a proof of concept thing, to motivate me to go further and make a nice PCB afterward...

Quote
A good differentiator in approach is not buying ridiculously expensive components!


Yeah, it's also my approach in life in general.... the more money someone tries to steal from me, the more suspicious and reluctant and demanding I become !  :-DD


Quote
It sounds as if you have come into contact with a nice... and generous, person.

I like how life likes to surprise you sometimes !
To be fair I highly doubt he has any clue about the value of this QUAD 33 ! He told me it was a NAD not a QUAD, to begin with !
To him it's just old junk he wanted to get rid of... and as he said, he was happy to give it all to me to make use of and enjoy in one way or another, rahter than resorting to dump it all. He said he was kinda sad we didn't meet just a short while ago as he dumped 100 times more stuff, and has only a tiny bit still left to give me ! Yeah, he seems a kind person, I quite like him even before he gave me this valuable QUAD 33 !   ;D  Well, as I said, with the missing button it's probably not worth much anymore sadly. Not that I intend to sell it anyway.. now I know it's valuable, I want to keep it !  :-//   Will service it and see if I can get it going again.


Quote
I'm glad the information from both of us has been helpful

Yeah I am always happy to hear from you and Shakal, you know your stuff and are passionate, yet not audiophools thanks to your technical/electronic background. So I always enjoy learning from lots of stuff you two, 1st class knowledge served on a silver plate, can't complain I have it easy  ! ;D
Keep it coming !  ;D


OK let's work a bit on the transport, see if I can get it going or not... that will be for tomorrow... 23H40 here again, time flies, still haven't had dinner, too late now, straight to bed !
 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #29 on: April 15, 2021, 09:42:05 pm »
OH !

Just realized, at the back of that QUAD preamp unit, it reads "Made in Huntingdon, England " ?!

Wow, now that brings some memories !!!

Used to live there ! 

It is indeed a small world!  ;D
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #30 on: April 16, 2021, 07:51:13 pm »
OK, let's be quick... 21H00 here and must go to work tomorro morning at 5AM, so alarm clock set at 3H30 AM ! I should already be in bed   :scared:

So quick...

Worked a little bit on the player this evening, on the CDM this time.

1) First tried to oil the top bearing of the pickup... to no available : somehow I just cannot find my bottle of machine oil ! Now I understand that my bench right now is a complete cluster fuck, I get that but still, it's big enough that I should be able to see it eh ? I swear I saw it yesterday just standing right in front of me by the scope.... but spent 15 minutes searching for it, no luck. It just has vanished in thin air, I am baffled... I am sure it's right there looking at me, screaming " Hey I am sure, can't you see or what ?! ". I am sure.

2) So next item on the list, was to check the blue Philips cap on the laser drive. Cut on leg of it so I can measure it reliably. Was nto disappointed. As you suggested these caps like to lose capacitance, indeed ! Supposed to be a 47uF one, measured at 20uF !  :o
So happy to have found the problem, I replaced it with an equally old one from my stock, but not regular radial one not a Philips of course... and it measured at 51uF so I called it good enough, at least for a quick test. It's only rated at 16V when the Philips one was rated at 25V but since it is fed by the TTL output of the decoder chip, I very much doubted that it would see anywhere near 16V anyway. Not ideal OK, but still, for a quick 2 minute test, good enough.  Was very disappointed when I tried to play a CD and it made no difference whatsoever !  :-//

3) So next item in the list was laser drive. I moved the laser adjustment pot just a hair CCW, and it made things worse. So turned it CW a hair... now works just fine, I have audio coming out !!!   :box:  Maybe during shipment the trimmer got disturbed a tiny bit, enough to upset the player.

However I am not happy about the fact that it turns out that the trimmer is turned ALL THE WAY CW  ?!  :o   I only barely moved it to get the drive to work, I swear, so that means it was already 98% turned CW.. strange ! I guess it's designed so that at the factory the player works with the trimmer set about half way, would make sense no ?  Maybe some douche bag "serviced" this player in the past, " screwdrivered " it, worn the laser out doing so, so now you have to turn up the power to the max just to get enough laser output for playback to work ? Hmmm... not looking good. Poor CDM is on its last leg then, I guess. .. could die any day, makes me sad. 


Anyway, there is still one BIG problem with the CDM :it works.... but only for 2 minutes at a time ! Ever encountered something like this guys ???

I mean, it does a weird thing, here goes :

1) Press PLAY, starts on the button, plays music just fine.
2) After a couple minutes or so, sound cuts out abruptly. No skipping whatsoever, it just cuts out all of a sudden
3) Then the turntable motor loses its mind and the disc starts to accelerate, accelerate, like a jet engine wannabe
4) After a couple seconds, the disc stops, fast (brakes are applied).


At this point, I can press PLAY again, immediately, and the player will play the music just fine, as if nothing weird at all had just happened !
... but after a couple minutes again it will speed up the disc, then stop it... then I can press PLAY again and the cycle repeats !

It is very repeatable. I didn't time it, but it feels like it always takes the same amount of time for it to cut out and accelerate the disc. At a rough guess I would say 2 minutes or so. Could time it if need of course...

Also, I swapped transport, and the black one for the Toshiba, does not misbehave. I let it play for like 10 minutes, changing tracks from first to last, then back to middle, to try to upset it... but no, it just works.

So, the white CDM is most likely at fault, not the main board. Making progress none the less !
At least now I know the pickup is probably just fine (other than the laser being close to dead), since it plays fine for 2 minutes, then plays fine again as soon as I press PLAY again just after the mishap.
Also, even if the pickup was somehow showing this weird behaviour, it still would not explain why the disc speeds up, would it ? I mean if I were the decoder chip, and the pick-up was sending me garbage... I would just stop playback and stop the disc, that's all... how would accelerating the disc make things any better ! 
So, my first guess is that the problem is not the pickup, but simply the turntable driving chain that's bad. OF course it's all a closed loop, everything is interdependent, I get it but... since we know the problem lies in the transport, not the main board, and since the pickup works fine for the first 2 minutes... my bet would rather be on the PCB that's at the back of the CDM, since it controls the turntable motor, and nothing else.  Service manual gives the schematic for this board. There is plenty of stuff on there, so one of the components must be bad.. would you agree with me, thus far ?!  :-//

I could swap the control board with the black / Working CDM to confirm this. Had a look, looks quick and easy and does not disturb the alignment of the pickup. It's well separated, great.

If it is confirmed that the board is bad, then I can start to trouble shoot this board. There is a lot of stuff on it so could be anything..  4 op-amps, 4 bipolar transistors,, a dozen resistors, 6 caps but all sub uF / low value ones, so probably ceramic or film, not troublesome electrolytics. Still, have seen film caps go bad, an ceramic caps as well, given the right circumstances..

...but there is also I see, two HALL EFFECT sensors ?! Hmmmm.... these things do go bad, in general... don't know about CD transports, but they sure go bad in laptop computers where they detect the closure of the lid, and they sure go wrong in the ignition system of all my old cars !  :palm:

Now, the fact the the problem has a definite "timing" aspect to it, fails after 2 minutes, every time, then "reset" itself once the motor is stopped and I press PLAY again....I guess excludes any thermal effect ? I mean the timing would be more random I guess. Plus, it probably could not reset itself so fast, pretty much instantly.  So it looks to me as if this timing aspect would more due to a capacitive thing going one somewhere, that would be reset once the main board cuts power to the control board.  So one of those small caps might be very leaky or something.

I really don't know, trying to make sense of this weird behaviour is not easy with my very recent and limited experience.... so please speak up my dear friends, tell me your thoughts !  ;D


Hmmm. ... just thinking of the laser drive circuitry. Guess I was wrong, laser output pin of thje decoder is probably not logic level, has to be analog and varying since it's in a closed loop using the "monitor" diode.  So yeah maybe the trimmer being all the way CW to get normal operation is not necessarily a worn out laser, maybe it's just some problem in the driving circuitry, something is off, causing the trimmer to have to be fully CW even with a healthy (enough) laser. Worth investigating... though it won't cause my main problem discussed above, so I won't spend on it for now. Fix the control board first.. laser driver second.


Anyway, please tell me your thoughts on it as I could really use your help !  :scared:

Now rushing to bed, almost 10PM already, not much sleep left for me, oh boy, gonna be tough getting up at 3H30, ohhhhh dear ....  :(



 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #31 on: April 17, 2021, 10:21:15 am »
Well getting sound is an excellent step forward.  :-+

It sounds as if you have one known good (black) CDM4 and one suspect (white) CDM4. I guess this gives you the choice of players for a project - the Toshiba if you want the CD373 style I2C front panel interface, and the CD371 if you want the simple front panel interface. I fully understand that you would like them both working.

I too would have hoped that the axial capacitor would have corrected the problem. Yes, I would have expected the laser current pot to be somewhere nearer the mid position for normal operation. The only way to accurately set the current, of course is to follow the procedure on page 4-2 of the CD371 manual - setting the voltage across resistor 3508 TP1 and TP2 to be 50mV and then doing the fine adjustment. I would strongly recommend this if you decide to swap be Black CDM4 into the CD371 to avoid blowing the laser due to over-current.

The spindle runaway symptom is a curious one. All of the normal causes would be main PCB based rather than individual transport related, for instance, losing the 11.2896MHz clock from the SAA7220, or maybe a DRAM chip fault. It sounds as if the 6805 microcontroller f/w is detecting the runaway and stamping on the brakes. I suppose it might be caused by loss of data but I've never seen it!

I suppose an intermittent ribbon cable connection from the main PCB to the brushless motor PCB might cause such a problem, but it's difficult to think that instant recovery on pushing the play button would be so repeatable,

Yes, you should be able to swap the brushless motor PCB between the transports - I've never done it, but the mounting pillars of the bottom bearing bracket are a close tolerance fit into the matching holes in the transport, so it shouldn't cause misalignment. It is a 4 pole motor with 2 hall devices. It if difficult to think of a fault that could make it run away rather than stop. The only adjustment pot on the board is a control voltage sensitivity pot, but I think if that went open circuit, it would cause the motor to stop, not run away. Those hall motors are very reliable though.

The Marantz CD75 Mk2 service manual includes checking procedure for the brushless motor, with waveforms and measurements (and pot setting) on page 4-5. Don't ask me why, of all the manuals, they decided to put it in just this one manual - or how many years it has taken me to notice it! ::)  It is downloadable from https://www.freeservicemanuals.info - it's actually listed as the Philips CD75 MK2 (in keeping with the very intimate family!)... https://www.freeservicemanuals.info/en/servicemanuals/viewmanual/Philips/CD75MK2/None/None/482272522118/.

My gut feel though, is that the White CDM4 has some sort of laser pickup problem. Try closely following the laser adjustment procedures by the book. If you can't achieve the stated values, then it's laser is probably dying. I will include my usual warning about ESD on the flexi-print ribbon when hanling the transports!

On the upside, it is possible to transplant the laser assembly from a cheap CDM4/19 equipped player - I wouldn't be surprised if you already had one in you now considerable collection!  ;D
« Last Edit: April 17, 2021, 10:23:18 am by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online shakalnokturn

  • Super Contributor
  • ***
  • Posts: 1436
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #32 on: April 17, 2021, 01:23:22 pm »
Otherwise a spare is available here:
https://www.leboncoin.fr/collection/1814733077.htm?ac=206978287

No clue about ESD precautions though.
 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #33 on: April 17, 2021, 03:56:30 pm »
That's a good price, I think that is from a CDM2 transport though (the Marantz CD45 used a CDM2/29). Not a show stopper, and good value considering that it includes the servo board that is built into the CDM2/29. Useful for spares.

There are a few main board component differences between using the CDM2 and CDM4 due to different laser/monitor diode and focus coil sensitivities. These are documented nicely in the CD471 /00R/00B/01R/05R/07R service manual (specifically) which covers the transition period between the use of the CDM2/10 and CDM4/11 in the CD471. If you look at the top right corner of the servo schematic page, there is a table of component differences (marked **) - it's a useful general reference for converting other players between the two transports. You will be able to find all the necessary passive components on the servo board in the listing.

You can find the relevant issue of the CD471 service manual here...  https://elektrotanya.com/philips_cd471.pdf/download.html

Of course, this makes it impossible to do direct swaps back and forward between the two.


P.S. I did actually wonder earlier whether the end-stop position of the laser adjustment pot on the CD371 with the white CDM4 might be due to some mismatch with the main PCB expecting a CDM2, or the white CDM4 being fitted with a CDM2 laser, or some combination (if that isn't too confusing!). It would be worth double checking the relevant component values on the PCB - for instance, the pot value and its series resistor are one of the differences.
« Last Edit: April 17, 2021, 03:58:39 pm by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #34 on: April 17, 2021, 05:45:56 pm »
Thanks again chaps for the infos and links. Good find Shakal for the spare parts...

It sounds as if you have one known good (black) CDM4 and one suspect (white) CDM4. I guess this gives you the choice of players for a project - the Toshiba if you want the CD373 style I2C front panel interface, and the CD371 if you want the simple front panel interface. I fully understand that you would like them both working. 

Oh yes I definitely like the Toshiba very much, have grown fond of it already. So I will do everything I can to get the white transport working so I can get both players in business. It is completely out of the question to use the Toshiba as a parts unit to keep the Philips going....  :-[

Quote
The only way to accurately set the current, of course is to follow the procedure on page 4-2 of the CD371 manual - setting the voltage across resistor 3508 TP1 and TP2 to be 50mV and then doing the fine adjustment.

Acutally from what I understand, the  " fine " adjustement is precisely setting that 50mV...

I meant to do it, but problem !  As you can see i the manual... the adjustment is intended to be carried out by playing a TEST CD, so with a particular audio content. Presumable a single / sinusoidal tone, of god knows what frequency and amplitude. Or maybe it's wide band white noie, who knows. Point is, it's not made to be performed by playing some random music... so I am screwed right there, Bohemian Rapsody just won't cut it  :-//

Also, they say 50mV, but 50mV WHAT ?  DC ? "RMS"/sine calibrrated cheap DMM ? or TRUE RMS ? Peak ? Peak to Peak ? using a scope then ?!

At least the procedure makes it clear that the base position for the trimmer should be about midway, so there is definitely something fishy about my player.

Quote
I would strongly recommend this if you decide to swap be Black CDM4 into the CD371 to avoid blowing the laser due to over-current.

Yes been thinking that too.  Could easily figure it out though : with the black CDM in place, I could just set the trimmer to see at what point it start skipping the audio ? That would mean that this particular position of the trimmer is where the laser is safe, barely getting enough juice to work properly ?
If even the black one rrequires teh trimmer fully CW like the white one, then most likely both pickups are fine and the problems on the main board... but again as said previously, without the test CD and more precision about what they mean by "50mV", adjusting the trimmer would not be pertinent  :-\


The spindle runaway symptom is a curious one.

That's my luck ! You have 100 times more experience than me yet somehow I get an obscure fault that even you have never encountered !   |O
Well, OTOH it makes it an interesting one to troubleshoot then, we will all learn something from it !  :)

I suppose an intermittent ribbon cable connection from the main PCB to the brushless motor PCB might cause such a problem, but it's difficult to think that instant recovery on pushing the play button would be so repeatable

Yes, bad connection would not be repeatable like clock work...

Quote
The Marantz CD75 Mk2 service manual includes checking procedure for the brushless motor, with waveforms and measurements (and pot setting) on page 4-5. Don't ask me why, of all the manuals, they decided to put it in just this one manual

Hmmm.... there is a one, full page about this in the CD371 service manual, haven't you seen it ?!  It's almost at the very end of the manual. Page 44 out of 46.


Quote
My gut feel though, is that the White CDM4 has some sort of laser pickup problem. Try closely following the laser adjustment procedures by the book. If you can't achieve the stated values, then it's laser is probably dying.

I guess it's not impossible... start with the most plausible causes failure before resorting to fancy exotic explanation... dying lasers being such a common thing on these old players, I guess it's good starting point...
We could for example imagine that the laser being on its last leg, based on the trimmer being fully CW, maybe after 2 minutes of being powered, it heats up and that disturbs it somehow, and takes away its last breathe of light. Then the player stops the disc and cuts off the laser, so it cools down and then the cycle repeats again. Since the junction of the laser is obviously tiny, it could explain that although its a thermal issue, the time scale involved is fairly short.

This, I can investigate. Again playing with the trimmer with the black trimmer will tell me if the trimmer fully CW is due to a worn out laser on the white CDM, or a problem on the main board. If I had a transparent disc, I could check if the laser goes of by itself when the sound cut occurs. No transparent CD here though...  But maybe I could hardwire the base of the transistor to Vcc to keep the laser powered up artificially, in the absence of a CD. I don't know...


Quote
I will include my usual warning about ESD on the flexi-print ribbon when hanling the transports!

Oh no ! Still have not thought of buying paper clips !!  |O
I try to be as careful as can be though, of course.  Just before pulling the cable, I ground both my hands by touching the BNC connectors on my scopes,then when I pull the cable I make sure I never touch the exposed metal / terminals, with my fingers. Once the transport is out, I grab my pair of tweezers, I ground that hand again via the scope, then I short all the pins on the flat flex using the tweezers. Then I set the transport aside.
Yes, I really WANT to buy paper clips, but every time I got to the supermarket I fucking forget !!!   |O


[quote}On the upside, it is possible to transplant the laser assembly from a cheap CDM4/19 equipped player - I wouldn't be surprised if you already had one in you now considerable collection!  ;D[/quote]

Hmmm.... taht would be useful indeed ! I do have a couple Technics players (the ones with the " MASH "DAC), which do have swing arms in them. They are definitely looking more recent than then old Philips 371 so I guess the CDM must be the one your referring to ! Will check shortly....



 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #35 on: April 17, 2021, 07:22:01 pm »
Acutally from what I understand, the  " fine " adjustement is precisely setting that 50mV...

I meant to do it, but problem !  As you can see i the manual... the adjustment is intended to be carried out by playing a TEST CD, so with a particular audio content. Presumable a single / sinusoidal tone, of god knows what frequency and amplitude. Or maybe it's wide band white noise, who knows. Point is, it's not made to be performed by playing some random music... so I am screwed right there, Bohemian Rapsody just won't cut it  :-//

Also, they say 50mV, but 50mV WHAT ?  DC ? "RMS"/sine calibrrated cheap DMM ? or TRUE RMS ? Peak ? Peak to Peak ? using a scope then ?!

At least the procedure makes it clear that the base position for the trimmer should be about midway, so there is definitely something fishy about my player.

You're right, the 50mV is the fine adjustment (I was mistaking it with the fine focus) - the master is beginning to make mistakes! :-[  From memory, this is a DC measurement. In the absence of the Philips test disc, you can just use a decent quality audio CD (data is data - you won't get problems with strong modulation on Bohemian Rhapsody it will look the same as any other signal). The test disc just a 'standard' for the reflectivity of a normal CD. Just make sure you don't use a CDR, that would definitely give the wrong value due to different reflection. You could try a few audio CDs and check that the reading is in the same range. The reading needs to be correct on Audio CDs anyway - these are what it spends its time playing, not test discs.

Quote
That's my luck ! You have 100 times more experience than me yet somehow I get an obscure fault that even you have never encountered !   |O
Well, OTOH it makes it an interesting one to troubleshoot then, we will all learn something from it !  :)

That's the spirit!  :-+

Quote
Hmmm.... there is a one, full page about this in the CD371 service manual, haven't you seen it ?!  It's almost at the very end of the manual. Page 44 out of 46.

I am indeed slipping! I must have seen it in the past, but was looking through the CD75 the other day and noticed it among the tests and adjustments in the front of the manual where I hadn't noticed it before. It's not normally something that you need to go looking for with these motors (my excuse anyway!).

Quote
This, I can investigate. Again playing with the trimmer with the black trimmer will tell me if the trimmer fully CW is due to a worn out laser on the white CDM, or a problem on the main board. If I had a transparent disc, I could check if the laser goes of by itself when the sound cut occurs. No transparent CD here though...  But maybe I could hardwire the base of the transistor to Vcc to keep the laser powered up artificially, in the absence of a CD. I don't know...

No no!... pulling the transistor base high will put maximum possible current (limited only by the safety resistors) through the laser, it will guarantee that you find the blown laser that you are looking for!  The TDA5708 regulates the Laser current (via the transistor) based on its input from the laser monitoring diode (the laser current pot works by reducing the current from the monitor diode that the TDA5708 sees).

Do you have a stack of blank CDRs anywhere? These normally include a transparent disc at the top of the blank discs as protection. That's where I got mine from. Unfortunately it won't help you see the laser output at the point of failure though (it is obviously producing output when you first press play).

You could try using the 'service positions', unfortunately you may be hampered by lack of working display. If you read carefully, it seems that in service position 1, the laser will stay on after pushing one of the <<search buttons. These may allow you to keep the laser illuminated long enough to observe the failure. Make sure you view the laser from a distance, nowhere near the focal point, that dim red glow is very bright in the IR spectrum. Another idea is to watch the output of the laser monitor diode (maybe tack a wire on at the laser adjust pot). You may be able to see the diode output reducing, or more likely, suddenly drop as when the laser control loop is no longer able to maintain output.

Quote
Oh no ! Still have not thought of buying paper clips !!  |O
I try to be as careful as can be though, of course.  Just before pulling the cable, I ground both my hands by touching the BNC connectors on my scopes,then when I pull the cable I make sure I never touch the exposed metal / terminals, with my fingers. Once the transport is out, I grab my pair of tweezers, I ground that hand again via the scope, then I short all the pins on the flat flex using the tweezers. Then I set the transport aside.
Yes, I really WANT to buy paper clips, but every time I got to the supermarket I fucking forget !!!   |O

As long as you are taking reasonable care, you should be ok. The Laser does have a capacitor and resistor across which should provide a little protection. I'm not sure how sensitive the photodiodes are though. The problem is that once the transport is out, it is mostly plastic so it is difficult to find a decent ground reference before touching the ribbon.

Good luck with the CDM4 search!
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #36 on: April 17, 2021, 08:00:58 pm »
Just a couple of thoughts.

1. The spindle runaway. Once in play mode, the SAA7210 will try to maintain its FIFO (held in the DRAM) as about (I think) 75% by adjusting the spindle speed to bring in more  or less data. If data stops, due to the laser dropping out, it might ramp the speed up to maximum. I don't know what the microcontroller does in this situation and how it decides when to hit the brakes.

2. If you like the Toshiba so much, you could use it as the basis of sound quality improvements (the schematic is the same as the CD371 in all quality relevant aspects), there is no difference. You can of course delay this until your other equipment is improved to the point where it makes a difference. The CD371 is most useful when implementing your own player as a project.
« Last Edit: April 17, 2021, 08:03:12 pm by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #37 on: April 17, 2021, 08:42:57 pm »

OK, just spent an hour fiddling with the player. I think I nailed it. You were right, looks definitely like the laser/pickup on the white CDM is on the verge of dying, on its last leg, last toe even.  Here is what I did, which led to that conclusion...

1) swapped control boards. Takes literally 30 seconds, it does not interfere in away way with the delicate assembly of the pickup, so no risk whatsoever to screw this up, even a child could do it.  I put the good control board from the black CDM, into the white/faulty CDM. Result : played fine for 5 minutes, was looking good but....then got a very scratchy sound for a few seconds (sounded just like a 30 year old dirty volume knob or something...), then sound became normal again, then shortly afterwards it did its usual thing, sound cut out, discs speed went through the roof, and then it stopped.  This alone is interesting... it did stop, but unlike yesterday where it would fail after a couple minutes, here it took a little bit more time. So it's not that repeatable after all.
So looked like the control board was not at fault... hence has to be the pickup somehow, as you suggested.  Tried to wind back the trim pot for the laser adjustment. It was 100% CW, but backing it just a split hair made it stop working. It really needed to be 100% to work, and even then I still got that scratchty sound at some point. So might suggest a worn out laser...

2) So, I then swapped CDM. That is, I installed the black CDM with the control board from the white one. Would it fail then ?
Laser trimmer was still set 100% CW.  At first it was weird : the CD was detect properly, the player would play it, disc was rotating along happily, looked all normal except... I had NO sound coming to my headphones whatsoever ! Eh ?! Player seems happy with the plckup since the disc is spinning normally...so why no sound ?!  I then started slowly turning the laser trimmer CCW to see if that CDM too needed 100% trim, or not.  Answer is  : NO !!!
As the CD was spinning with no sound, as I was winding back the trimmer, at some point sound came back !!!  :D
So I guess the laser was over driven and the eye pattern must have looked all clipping and saturated or something ?! Then I kept turning the trimmer CCW until sound would start having problems. At some point it started producing the same scratchy sound that I had before with the white pickup. So looks like this player does not skip the audio when laser is too weak.. instead it makes this scratchy sound. Why not...
Point is : it started becoming scratching when the trimmer set about .... MID WAY !!! YESSSS !!!!!   :D
So clearly the driver circuitry on the main board is fine, and a decent laser works fine at about 50% trim, no worries. Slight nuance : there is some "hysteresis" to this... I mean : at 50% trim, the CD will NOT play, won't detect teh disc. Need to increase the trim a bit, I don't know 75% maybe, far from 100% though. Same thing when I try to change tracks : at 50% trim I often run into problems, player can't manage and stops the disc. So in practice I have to set it to more than 50% to have ti detect/start discs reliably.  Still, sounds reasonable to me... 50% is for a brand new laser, this one is 30 year old !! And it still plays fine at 50%, needs the extra turn only for detection and track changes, won't blame him ! No ? What do you think ?!

3) Once I had rewind the trimmer to halfway or thereabout, and started getting that scratchy sounds... I rewound it even further, very slowly, to see what would happen. Glad I did : guess what happens if you do that and you lose the signal for good ? YES, player spins the disc super fast then stops it !
So this behaviour was indeed indicative, at least on this particular player, of a weak/lost signal !!!


So with all that, I came to the conclusion that both control boards were fine, and it's just a completely worn out pickup on the white/Philips CDM.  >:(

Will look inside my two Technics players to see what reference CDM they use, and report back. You will tell me if I can plug them safely into the little Philips...

Anyway, making progress so quite happy despite the bad news !  :-//

 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #38 on: April 17, 2021, 09:02:22 pm »
Good test strategy - it sounds as if you have a good handle on the situation now, particularly the runaway effect of insufficient laser output (I don't think I've ever wound one back that far during operation). I would beware of running the black one at the end-stop any more though, it will probably shorten its life. Yes, too much power will probably cause the photodiodes or input circuitry to saturate.

Good news on the motors - I think you can probably see what I mean about the size of those shafts compared to the average brushed motor.  :)
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #39 on: April 17, 2021, 10:42:42 pm »
I would beware of running the black one at the end-stop any more though, it will probably shorten its life.

Well yes of course ! Now I know it works fine somewhere between 50/75%, not going to burn it at 100%.... plus that will never happen anyway : now that the diagnosis has been established for the Radiola / white CDM, I don't have any reason to mess with the good black one from the Toshiba :  So I put it back inside the Toshiba whee it belongs, and put the Toshiba player all back together ! While I was at it I put some contact cleaner in  the tray switch taht was causing me random weird problem the other day.. and exercised the switch 100 times by hand. Should take care of the problem, we shall see in the long run. Gave it a test ride, seems to work fine. Just love this player, don't think I want to mess with it. Will rather use the Radiola as a test bed. Needs a new pickup anyway already, and extensive work to get the display running again. So... it's already going to be Frankenstein-ized anyway, so might as go the extra mile and use it as a test bed for audio improving mods like the two of you have made.


Quote
Good news on the motors - I think you can probably see what I mean about the size of those shafts compared to the average brushed motor.  :)

Yes, generally speaking these brushless motor inspire so much more confidence than the shitty tiny skinny brushed ones. Plus the brushless look cool (how scientific is that  for an argument !  ;D) and beefy, indestructible, and easy to take apart, and larget diameter. They probably have more torque than the shitty brushed ones.  And that one piece cast resin  piece is nice too, especially sexy in white. I can't get enough of looking at it. There must be something weird in me... or maybe that's what it is to be a "nerd"  :-//  So be it, I am what I am ...

Anyway, with the Toshiba all buttoned up, I could free some space on the work bench.... just enough to lay my two swing arm Technics players.
See picture.... they are similar models but not the exact same. The tray mechanism is 99.99% the same as the old Philips, incredible. Only tiny difference so as to accommodate the mounting points of the later CDM transport, but that's about it ! So for example I could reuse the tray, tray switch linkage pieces, motor, gear and belt to fix and old Philips !  :D

Quote
On the upside, it is possible to transplant the laser assembly from a cheap CDM4/19 equipped player - I wouldn't be surprised if you already had one in you now considerable collection! 

Good !!! Just checked my Technics players, they both have that CDM4/19 in them !!!  :D  Looks indeed like shittier construction, and shitty looking brushed motor... but the swing arm and pickup look like a carbon copy of the CDM 4/11 indeed !  :D 

So.... time to swap swing arms with the Technics.... tomorrow !

Good night....  :=\
« Last Edit: April 17, 2021, 10:59:49 pm by Vince »
 

Online shakalnokturn

  • Super Contributor
  • ***
  • Posts: 1436
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #40 on: April 17, 2021, 11:28:17 pm »
I suppose the runaway is what you get when the SAA7210 can't recover the clock correctly from the input stream. I don't know why it would react specifically that way though.
On other players I've noticed that you can often trigger the speed runaway by getting the VCO adjustment too far off.

Agreed that the laser seems to be on its last leg, all the same in case it came from a smoky environment (any brown/yellow deposit if you wipe the tray with IPA? No not beer!) you may want to re clean the lens or as a last attempt remove it to clean the under-side and prism. I can remember doing it on a swing arm model before, can't remember which though.
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #41 on: April 18, 2021, 12:00:18 pm »
Cleaned it again, still get the scratchiness every now and then, but it's been running for 20 minutes so far, and still going so...not dead but not trust worthy either to me....  Still, working plenty well enough to now let me turn to the display problem, that's for sure.

 Not a smoker CD player it seems, no residue when cleaning the CDM, and all the white plastic parts in the mechanism, all look brand spanking new, snow white... whereas in the Toshiba all these parts are significantly yellowed.

I just checked the eye pattern from the white CDM so I have a reference point so I can assess the improvement (hopefully) when swapping the swing arm with a CDM 4/19. Glad I did.. see below.

Used a x10 probe. Laser trimmer again set to 100% or else it just won't work as per usual. This results in a roughly 2Vpp signal, which is excellent given the service manual suggests "around" 1.5Vpp. Now, from working on a previous player, can't even remember which one, posted it on EEVBlog though (maybe the CDM12.1 I replaced in my dad's 3 disc carousel changer from his crappy Philips integrated stereo system) I noticed that I could reduce the laser output A LOT before it would start misbehaving. I remember something like 100mV ! At 100mV the eye pattern was still looking good and still playing fine !  :o

Now, with the white CDM here, look what happens (second picture) : 2Vpp at 100 trim. Then I rewind the trimmer juuuuuuuust a split hair, to get it to produce this scratchy sound just before it stops working altogether and stops the disc. See what's the result ? Amplitude has not changed, still a very healthy 2Vpp.. HOWEVER the eye pattern becomes extremely blurry, can't even see it anymore, it's like a fuzzy cloud, an aurora borealis or something !  :o

So the problem is not a weak HF signal, it's strong (needs 100% trim though, of course...), it's a " blurriness " problem ?!  Focus problem rather than weak laser?!  I guess either way it does not matter... pickup still needs replacing... but the point is to understand what's going on, as much as getting the player working properly and reliably...

« Last Edit: April 18, 2021, 12:09:48 pm by Vince »
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #42 on: April 18, 2021, 02:40:31 pm »
OK swapped the swing arms with one of my two Technics CDM 4/19. Just like the spindle motor control board, it's a 2 minute of a few screws and that's it.

With that "new" swing arm, the Philips worked (which is a good start...), and according to the eye pattern, it worked much better, in that although it's tired as well and needs near full trim to be able to detect a disc and switch track reliably, at least when it's playing and you rewind the trimmer so to speak, it does not die instantly with that aurora borealis pattern. Instead, as you would expect, it still plays but of course the HF signal amplitude progressively decreases, but still looks like a clean/stable eye pattern, and at some point obviously it loses sound. It loses sounds at an amplitude of about 1 volt, which is much better than the original arm/pickup.  However as said before, although it can still play music fine at this level, its not strong enough a signal to be able to detect a CD when you insert it, or to change tracks. For that, you still need to get near full trim, which gives 2Vpp like the original arm. Looks like 2V must be what the HF amp is capable of producing. Past that point, if you keep turning the trimmer to get the last 5% out of it, amplitude does not increase anymore. Does not clip or distort either. Instead what happens is that the DC offset decreases, by about one volt from where it used to be. So to the sweet spot I guess is to set the trimmer to 95% where I get that 2V amplitude, where the disc detection works reliably, and just before the offset starts sinking.

Worked fine then after a short while things suddenly started wreaking havoc. A would lose the HF signal completely, and the pickup/Arm would make a faint " clic clic clic clic "sound indefinitely. Looks like I fried the laser for good eh ?! Yes, paper clips buy I will...

So swapped swing arms again, to give the white CDM its original arm back. I set the laser trimmer very precisely using the scope, using the "technique" described above.... and well, seems to work "fine"... for the 30 minutes that I tested it, changing tracks often to try and provoke a failure.

So I will leave it at that for now, and now switch to the display problem.

Will get that MM5450 in DIP package first, some prototyping board and cobble something crude, quick 'n dirty with just the first couple digits as Gyro suggested. Just as a proof of concept. If I can get that working then that will motivate me and I will get a PLCC version of that chip and go through the trouble of designing a replacement PCB for that module, using the original displays.

 

Online shakalnokturn

  • Super Contributor
  • ***
  • Posts: 1436
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #43 on: April 18, 2021, 03:50:00 pm »
Until now it sounded like a weak laser, now with your latest measurements I'm not so sure...
 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #44 on: April 18, 2021, 04:37:02 pm »
You're becoming quite the CDM mechanic! I'm glad you didn't run into any problems with the arm swap procedure.

I'm with shakalnokturn... slightly confused. It would be really unlikely to get two CDM4s with weak lasers - but please do buy some paperclips!  So it is only the CDM from the Toshiba that doesn't require 95% on the laser adjustment pot?

1. A couple of random thoughts. Did you check the component values to confirm that the PCB is definitely CDM4 'ready' (values from the CD471 manual)? I'm not sure quite how that would tie in with the various transports but this CD series did span the transition form CDM2 to CDM4. At least confirm the marked value of the pot.

2. In the case of correct playback but inability to initially detect the disc, have you tried adjusting the focus offset? If you do, then carefully mark the wiper position so that you don't run into problems with a tweaking both pots at the same time. I may make use of the baseplate drilling diagram myself - I suspect that  it holds for the CD371 too.

Now you at least have proper operation then yes, it sounds a good plan to have a go at the display project.


Just out of interest, I have attached a project article from Elektor Magazine from back in 1992, which illustrates the way it was possible to purchase CD player OEM kits from Philips. Several small fledgeling manufacturers got a start into CD products this way. I forgot I had this.
Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: shakalnokturn

Online shakalnokturn

  • Super Contributor
  • ***
  • Posts: 1436
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #45 on: April 18, 2021, 08:01:27 pm »
A couple if thoughts on your last measurements...
I'm leaning towards a tracking or VCO problem but it's merely more than an educated guess at this point.
Maybe worth checking the small electrolytics around the SAA7210, power supply decoupling and VCO section.

Testing the doubtful transport in the working Toshiba could also help further diagnostics. Taking care of not abusing laser power and possible component differences of course as Gyro mentioned.
 

Online Gyro

  • Super Contributor
  • ***
  • Posts: 6645
  • Country: gb
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #46 on: April 18, 2021, 09:03:50 pm »
Testing the doubtful transport in the working Toshiba could also help further diagnostics. Taking care of not abusing laser power and possible component differences of course as Gyro mentioned.

Agreed, I think it's the only way to move forward if you want to be sure of the situation.
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #47 on: April 19, 2021, 03:36:14 pm »
You're becoming quite the CDM mechanic! I'm glad you didn't run into any problems with the arm swap procedure.

Thanks, but that would be a rather shady backyard mechanic then !  :-[  I didn't observe any procedure for the arm replacement... didn't even think of reading it... thought it was pertaining only to pickup replacement, not complete arm sub-assemblies. My bad indeed.
I simply unscrewed the bearing backplate as they call it, and screwed it back on, no more no less, and all went well. I mean the eye pattern  before/after is 100% the same... it it were that sensitive, I would have expected wild  degradation (or improvement !  ;D ) of the eye pattern or player behaviour, but saw none whatsoever. Sheer luck ? .... I mean, the procedure says that you can adjust the angle by moving the back plate then securing it into place with the screws. Trouble is that this plate cannot move. It was stuck in place once I had removed the screws. Had to pry it off to get it to come off the CDM ! So much for adjustments....

Quote
I'm with shakalnokturn... slightly confused.

I am VERY confused... so if you are only "slightly" confused, that's good !  ;D

Quote
It would be really unlikely to get two CDM4s with weak lasers

I have to say I was surprised as well that the other arm required almost full trim to be reliable...


Quote
but please do buy some paperclips!
 

I am true to my word. See below.

Quote
So it is only the CDM from the Toshiba that doesn't require 95% on the laser adjustment pot?

I don't know what the Toshiba requires. When I tried I was not back then scoping the eye pattern hence not fiddling with the laser trimmer... so it was therefore using full trim too, since it was to that and I had not touched it yet at that time.


Quote
1. A couple of random thoughts. Did you check the component values to confirm that the PCB is definitely CDM4 'ready' (values from the CD471 manual)? I'm not sure quite how that would tie in with the various transports but this CD series did span the transition form CDM2 to CDM4. At least confirm the marked value of the pot.

Just realized... there is an addendum toward the end of the manual... it gives all the CDM4 specific changes. New main board schematic and new laser adjustment procedure too !
The CDM4 schematic does not say what is the value of the laser trim, sadly. However on the first/ CDM2 schematic, it's 1K , and my board I have a 4,7K !  So I guess that means it's been updated for the CDM4 and all ought to be well... ought to.


Quote
2. In the case of correct playback but inability to initially detect the disc, have you tried adjusting the focus offset?

No !  ... because I don't have a good understanding of how this trimmer affects the operation of the drive. I don't touch things that I don't understand.... and since you have not taught me that part yet, I carefully avoided messing with it....

Quote
If you do

I just did !  :scared:  since you talked about it, I somehow considered it meant I was allowed to !  :-//

Quote
, then carefully mark the wiper position so that you don't run into problems with a tweaking both pots at the same time.

.. did not work. All I have is big white tyre marker... it's too big and the ink is too fluid : as so as I touched the trimmer, the ink by capillarity instantly spread all around the wiper shaft, rendering the exercise futile....

But since there is a procedure to adjust focus anyway, I though worse case scenario is I screw things up and so what, I just reset the trimmer using the procedure... that's what it's there for after all...
so I looked at the eye pattern and turned the focus trimmer a split hair either direction. Zero change. so turned a couple hairs.. still no change.
Turned it dozen hairs... still no change. turned it wildly, full lock on both sides.... still no bloody change ! So I just put it back mid-way.
No matter how you set the focus trimmer, from 0 to 100%, it does not affect IN ANY WAY SHAPE OR FORM, the eye pattern NOR the behaviour of the drive, ie it doesn't drop sound, no skipping, no disc stopping. Still the exact same performance when detecting CD's or changing tracks... this focus trimmer has absolutely NO EFFECT whatsoever ?!!!  :o

Makes zero sense, you will agree... so it's like the trimmer is open-circuit or something.. which is extremely unlikely of course.
Maybe some nearby electrolytic cap leaked and corroded/cut a trace related to the trimmer ? Doubt it, the top side of the board looks pristine...


[quote}Just out of interest, I have attached a project article from Elektor Magazine from back in 1992, which illustrates the way it was possible to purchase CD player OEM kits from Philips. Several small fledgeling manufacturers got a start into CD products this way. I forgot I had this.
[/quote]

Wow that was cool, thanks !  :D  Didn't know about such things ! I doubt any major manufacturer would do that today... that was very nice from Philips indeed !!!
That said, by the time you have added the time and money required to R&D and build prototypes, then your own final product... you would be better off buying an off the shelf player I suppose !  But still, it would the DIY guy to design his very own unique player if he fancied that.


« Last Edit: April 19, 2021, 08:55:15 pm by Vince »
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #48 on: April 19, 2021, 03:48:49 pm »
Maybe worth checking the small electrolytics around the SAA7210, power supply decoupling and VCO section.

Yes I think it's time to pull the main board so I can inspect it closely on both sides. Check for corrosion/leaked caps, and whatnot.
Time also to check the basics : all the power rails. Maybe one is bad and affecting the performance and operation of the big analog chips.
Worth recapping all that area of the board. Not that many caps anyway so should be fairly quick and cheap.

Quote
Testing the doubtful transport in the working Toshiba could also help further diagnostics.

Yes that sounds like a plan, should tell us some things indeed... will do that.  Poor Toshiba, I have only just put it back together... going to strip it again. Not sure he will forgive me.....
Will open the Toshiba and solder wires so I can check the eye pattern while experimenting with the transports.


Quote
Taking care of not abusing laser power and possible component differences of course as Gyro mentioned.

Will take note of the HF signal amplitude with the Toshiba's original CDM, so I can reset it to where it was, after my experiments, then I will set it half way and swap transports.
 

Online Vince

  • Frequent Contributor
  • **
  • Posts: 717
  • Country: fr
Re: Vintage CD player repair : Philips CD 371 AKA Radiola CD 1371
« Reply #49 on: April 19, 2021, 05:34:49 pm »
OK, live results, Toshiba is playing music as I type this.... soldered wires to check the eye pattern, and checked trimmer position and overall behaviour.

In short : easy, it was 100% as the white CDM was in the Philips ! 98% trim... ie full lock then back a tiny bit to get rid of the unwanted offset that appears at full lock, and no more. Amplitude 100% same as well : 2Vpp. Behaviour too : if I try to go 100%, additionnal offset appears and playback/disc stops. If I rewind the trimmer, it behaves 100% like the CDM4/19 I pinched from my Technics : I won't get an aurora borealis, but rather I will get the expected progressive drop in signal amplitude, until it starts making this scratching noise then stops. Level wise, again 100% like the Technics : it stops working when I get to about 1Vpp.

So looks like the Technics was 100% fine until it died suddenly  :-[
Also show that the Philips laser trim set at nearly full lock is not that weird....

Also, check the manual, the CDM4 addendum. Revised procedure for coarse/baseline adjustment; you need to measure the total resistance formed by the trimmer and its series resistor. The latter is 100ohms and the trimmer is 4.7k. so that means the trimmer must be set at 900ohms, that's only 19% !  Take into account the worse case scenario when including tolerances (assuming say 5% for the series resistor and 20% for the trimmer), then that's a 5640ohms trimmer with a 105ohms series resistor. 895 / 5640, that's about 15% !!!  So you are already near fully lock CW !  :o
Add variations in laser output, then once you do the fine adjustment yeah, being dead close to full lock is not at all improbable, eh ?!

OK, so now that I know how the Toshiba performs, eye pattern amplitude and trimmer setting...I can remove its CDM and replace it with the white one.... taking a deep breath... what will we find.... STAY TUNED FOR THE NEXT EPISODE... NEXT WEEK !   In the mean time you can subscribe to my channel and donate on Patreon to support my channel, new cool merch coming soon !  :scared:
No not my kind, all too common these days....  :-\

« Last Edit: April 19, 2021, 06:47:01 pm by Vince »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf