Vintage CD player repair : Sony CDP-291 with transport issues...

[Vince]

Going OT a bit (though I didn't start it  ) to the Technics SL-PJ25. I found the service manual. In terms of transport and electronics, it's a very complex beast compared to the Philips ones. There are pots for adjusting eye patterns, PLL jitter waveforms etc that you simply don't have to worry about on the Philips. Given that the aim of both is simply to present the right bits to the DAC at the right time, they seem to have gone strangely overboard. Bits are bits after all. It does have the Technics MASH DAC though, which was well regarded at the time - I can't find the datasheets for the ICs though. I suspect that it is going to be something of a major project if it doesn't work!

The service manual is here... https://elektrotanya.com/technics_sl-pj25_cd_player_sm.pdf/download.html

Yep, there is a full row of orange trimmers right next to the track for the coil. Easy to spot on my pictures.
Yes I am sure it must be a lot of "fun" if one needs to fiddle with all of them to get the thing working to spec ! 

Will do my best to fix it, we will see how it goes...
That said if I fail to fix it, I would still keep it, as it's sucha uncommon and nice piece of engineering and build quality.

Nice to hear the MASH DAC is good... didn't even that "MASH" referred to a DAC ! 
The SL-PJ25 makes no mention of it on the front panel. However I have a couple other Technics players, a SL-PG200A and SL-P277A. Front panel look 90% similar. Both of them feature a huge "MASH3 markng on the tray face plate. Now I know what it refers to ! 
I first go the SL-P227A, which is a very sorry state. Very dirty outside, some rust on the chassis bottom plate, and a couple plastic bits broken from the transport... the clamping mechanism was dislodged and moving freely inside the cabinet... put it back together as best I could, and somehow it still reads CD's !    I kept it only because I noticed it had a swing arm, which surprised me. Also, a nice detail... it is the only player in my entire "collection" where the headphone output can actually play loud ! In all my other player, whether they feature a volume control or not, it won't play loud. I use the headphone output to fix all these players, as I have only one CD input on my amplifier, already used for my main player, the one I use to listen to music at the bench... don't know if one can connect another CD player (the device under test I mean) to the other inputs of the amp : Phono, Tuner, Tape1, Tape2... haven't checked the manual for the amp, but I guess each input expect a different signal amplitude and might apply some analog "processing" different on, each type of input. I don't know, maybe some filtering/bandwidth limiting tailored to each type of device... something like that...

Anyway, I intended to "restore" that player, treat the rust, give it a good clean, try to super glue the broken plastic bits back onto the transport... try to at least. Now that you are telling me that this MASH DAC is worthy, that's another reason for me to keep it...

The second player, 99% similar, also a swing arm, sold for part. What the seller did not say, is that the player clearly got dropped from the top of the Eiffel tower !     Wow... for parts it is indeed ! Though I could use it to help me fix the first player. Somehow, despite massive mechanical damage, it still powers up and the disc spins.. but it won't read it.



Toshiba : tried a Philips remote, indeed it works, hjust tried ! Good to know...
Luckily the player came with its original Toshiba remote control. First time I see a remote where you can select the "index". Don't even know what that means ! Maybe an audio track can be further divided in sub-tracks, and the "index" lets you navigate from one sub-track to the next.... don't know. Never had a music CD that had indexes ?! Maybe it could be useful for something like an audio book or something ? Lots of content so a track could represent a chapter, and you could further divide a chapter in sub-sections... dunno.

Anyway, "great" news : while trying the remote control(s) on the Toshiba, I eventually witnessed the player misbehaving !  YES, there is something that needs fixing in this player after all ! 

Symptoms :

- while the CD was playing, I could hear a weird noise coming from the cabinet, louder that I found acceptable. Thought oh no, the spindle motor is on its last leg, bad day ! But, I pulled the top cover and found that instead, the problem came from the DC motor that operates teh tray ! It was constantly running ! Tray was already closed, CD was being played, yet bloody motor was still trying to close the tray ! 
I stopped the playback, open the tray, closed it... and the motor stopped as expected. Did not misbehave anymore, hmmm.....

- Later, in the middle of playing, suddenly playback stopped, and the VFD displayed the TOC, as it does following the insertion of a disc ! So I had to press the Play button to get it going again.

- Later again, as I was operating the tray a few times to test it, it opened only 80% of the way then instantly moved back and closed ! So didn't have time to insert a CD.

It's all random and weird.. however it all adds up, makes a consistent picture, I think, if we had a dodgy micro-switch, the one that detects that the tray is closed. So might have to replace it. Looks like a bog standard tactile switch though, nothing special, soldered directly to the motherboard. Same kind you find for all the buttons on a front panel.

[Gyro]

Just to ve clear... you mean, the "map" of track numbers that I see on some players ? A "grid " populated with track numbers ? There is a special chip, H/W required to implement this functionality, the main CPU can't be bothered ?
Looking at the pic I took of the main board of the Toshiba, I see only one unpopulated chip, a big 24pin DIP chip, at the very bottom right corner of the board, right by the right side of the DAC.. is that it ?

Yes, that's right. The non-fitted 24pin chip is an EEPROM - I never used the function but it presumably remembered the favourite tracks for a number of discs. The 'map' of track numbers takes up a lot of display segments, so the display driver probably has to sacrifice these in order to display simultaneous track and time.

[Vince]

I would check that ribbon cable carefully.  I used to see a lot of them fail in Sony changers of that vintage.  It flexes every time the tray is opened or closed, so they can develop open conductors.  Check it for continuity since any breaks can be practically invisible.

You mean the long and wide green flat flex that goes from the front panel to the transport ?

It does not flex at all, never moves. It's connected to the "BD" board under the transport.

Well, it tilts a quarter inch up and down when the transport tilts upwards to clamp the CD, it's a ridicule amount of flex given how long the cable is, no ? you mean such a tiny movement is enough to break traces in the cable ?! 

Anyway, not taking any chances, so I checked continuity methodically between both ends of the cable... I get a sold connection on all 22 conductors.

Pulled the front panel to get better access. Now I have it apart, will be easy to do the next step : probe all power rails on that board to see how they are doing, especially ripple wise, in case we have a tired decoupling cap somewhere....

The symptoms though really point toward a failed driver IC. Its output stages must be shorted to full blast mode or something...

[Vince]

Yes, that's right. The non-fitted 24pin chip is an EEPROM - I never used the function but it presumably remembered the favourite tracks for a number of discs.

Ah OK ! It looks more sophisticated than I first assumed, my bad  ! 
So looks like an audio CD can be identified uniquely, there is some ID string or checksum or UUID or something, stored in the TOC, so that the player can identify the disc when it is inserted. EEPROM so that it can remember the list of favorite tracks for the various discs, even if you power it off....hmmm, sounds like a neat feature, like it !
I guess it needed an external EEPROM since the MCU's 30 years ago didn't have a built-in EEPROM, or at least it was nowhere near widespread/common as it is today...

I have a Philips CD824 (picture below, the one at the very bottom), with an "FTS" feature, think it stands for "Favortite Track System" or something... sounds like a similar feature as what you describe. Would be fun to read the contents of itrs EEPROM (if it's old enough to have an external one, not sure....), to read the discs ID, look it up in some disc database and find out what discs / music the previous owners listened to ! 

[Gyro]

Yes, there's all sorts of information buried in the subcode data - including CD Text (Album Title, Artist, track names etc), that few players support. I have a Kenwood one that does and has a scrolling dot matrix ascii display - it's a bit like DAB radio text displays.

[shakalnokturn]

Awww! Seeing those player stacked up reminds me of my collection still in cardboard boxes since the move.
What ever garage you're trying to build be sure it's going to be too small it's going to be hard to stop now... 
You're right about the drawer position switches they're are a common problem.
You can use any line level input on your amplifier. (Not Phono or Microphone.)

[Vince]

Drawings for the garage attached below ! 

House is 60m2 , garage will be... 60m2 too !

Would make it 150m2 if I could, but yard is too small and so is my salary.. gotta pay property taxes on garages too ! 

I already know it's gonna be too small, because 20% of it will be to make a cellar, a third / central part for a second/week-end car, and the last third+ needs to accommodate my stock of wood and woodworking bench and power tools to go with it... then I need lots of space to store the tons of tools and equipment that my soon to be 76 year old dad will be donating to me. If by some miracle there remains a little space for some shelves... yes, I will be using that to store electronic stuff.... but I already have my collection of old tube Tektronix scopes so... not much space will be left for Cd players or anything else, I anticipate !

Line level ? Sounds like standardized signal amplitude ? That would be cool indeed ! I noticed that every CD players I have always specifies : "line out, 2V output". RMS I guess ?  Peak ? Peak to Peak ?  So "line" level is 2Volts then.. ;good to know.

So I can wire my devices under test on the Tape or Tuner inputs then, cool... that will make working on stuff much easier indeed.

[tautech]

    
 
You need to introduce yourself with that pic in the TEA thread Vince.

Now we know why those old Teks are in short supply in the EU ! 

[shakalnokturn]

A slight case of boat anchory...

[tautech]

A slight case of boat anchory...

Someone has to save them from the tube pilferers !

[Gyro]

Someone has to save them from the tube pilferers !

Same with the Philips CD players. TDA1541As go for stupid sums on ebay! Most of them are re-marked fakes from China, either complete fakes that simply cook or 'uprated' by adding single crown or double crown markings.

The only way to guarantee a genuine part these days is to pilfer one from an old player.

[Vince]

   
 
You need to introduce yourself with that pic in the TEA thread Vince.

I am not sure I qualify for the TE club ?! ... will say hi anyway, bandwidth being cheap these days.

[Vince]

Someone has to save them from the tube pilferers ! 

Exactly ! Though not my primary intention at all, it's none the less a valuable side effect...

Seeing people harvesting the tubes from these scopes and then dumping the scopes, leaves me speechless. They don't deserve to live...

However, in my somewhat sizeable experience buying these things, I have to be honest the pilferers are a minority. Think I came across maybe 3 of them, really blatant ones. Most other people just want to flog these old things they got in house clearing or in an auction as part of a lot, but don't know squat about the tube "market", they are just the random Joe who wants to ma ke a buck or two from this anchor, rather than dumping it. Then at the other end of the spectrum you  scope that belonged to the old man that just died, son want the scope to go to a good home and is asking fair money. I even have a few who asked me to give them news of the upcoming restoration !
You get the whole spectrum of people, just like on any subject... human kind is diverse...

[Gyro]

Just reading back through the thread, I noticed I missed a couple of questions ...

Toshiba : tried a Philips remote, indeed it works, hjust tried ! Good to know...
Luckily the player came with its original Toshiba remote control. First time I see a remote where you can select the "index". Don't even know what that means ! Maybe an audio track can be further divided in sub-tracks, and the "index" lets you navigate from one sub-track to the next.... don't know. Never had a music CD that had indexes ?! Maybe it could be useful for something like an audio book or something ? Lots of content so a track could represent a chapter, and you could further divide a chapter in sub-sections... dunno.

Yes, 'Index' is a sub-division of a track, it's defined in the CD 'Red book' spec but hardly ever used. The only CDs I found it used on is the double disk set of Andrew Lloyd Webber's Phantom of the Opera. Each disc is completely Track 1, but with incrementing Index!  You get things like this on the earlier players which were adhering closely to the spec, but on later players, manufacturers no longer bothered supporting them. The same with 'de-emphasis' - similar to RIAA equalisation or vinyl - it was used on some early CDs to improve SNR or high frequency quality (probably mainly on the first 14 bit DACs). If you look at the schematic of the analogue stage after the TDA1541, you can see a couple of JFETs which are used to switch frequency response modifying components. Later players implemented it in the digital filters incorporated in their delta-sigma DACs or stopped supporting it entirely.

Anyway, "great" news : while trying the remote control(s) on the Toshiba, I eventually witnessed the player misbehaving !  YES, there is something that needs fixing in this player after all ! 

Symptoms :

- while the CD was playing, I could hear a weird noise coming from the cabinet, louder that I found acceptable. Thought oh no, the spindle motor is on its last leg, bad day ! But, I pulled the top cover and found that instead, the problem came from the DC motor that operates teh tray ! It was constantly running ! Tray was already closed, CD was being played, yet bloody motor was still trying to close the tray ! 
I stopped the playback, open the tray, closed it... and the motor stopped as expected. Did not misbehave anymore, hmmm.....

- Later, in the middle of playing, suddenly playback stopped, and the VFD displayed the TOC, as it does following the insertion of a disc ! So I had to press the Play button to get it going again.

- Later again, as I was operating the tray a few times to test it, it opened only 80% of the way then instantly moved back and closed ! So didn't have time to insert a CD.

It's all random and weird.. however it all adds up, makes a consistent picture, I think, if we had a dodgy micro-switch, the one that detects that the tray is closed. So might have to replace it. Looks like a bog standard tactile switch though, nothing special, soldered directly to the motherboard. Same kind you find for all the buttons on a front panel.

Yes, that is almost certainly that tactile switch on the PCB gone intermittent. It is the only limit switch on the whole transport and detects when the drawer is fully open or fully closed. A little contact cleaner dripped in might cure it, but replacement is easy. It won't be an alignment issue because the mechanics have a spring mechanism with good travel.

[Vince]

Thanks for the info Gyro, I will go to bed in 30 seconds, feeling a bit smarter indeed...

Will go and replace that micro-switch on the Toshiba. Will salvage a switch maybe on that Technics players that fell from the Eiffel tower. If I take one from the almost never used buttons, they should have next to zero wear on them.
Not sure how contact cleaner would manage to seep into that style of switch though ? Looks kinda sealed...

[shakalnokturn]

May I call that a mistake...?

Wear is one thing, not what seems to cause those switches to fail most of the time. If anything it's black layer of oxide (I don't know the chemistry at play here) that causes them to have poor contacts so seldom used switches are actually more prone to this because there's no mechanical action to "clean" them

They're not sealed and a spraying and very thourough clicking can work wonders.

[Vince]

Ah...OK.

I said that because every time I had a micro switch like these fail, in whatever piece of equipment, it was always the one that got the most use, that started failing, getting intermittent. Happened on my alarm clock, washing machine... and even my CDC486 Philips : I recently noticed the PLAY button is getting intermittent too now !

OK, will try some contact cleaner first...

[shakalnokturn]

Maybe wear then 
I could be wrong...

[Vince]

Probably too much trouble and also assumes that the other driver outputs are ok. Pins 10 and 11 should give you the answer anyway.

OK, let's get back on track.... this thread is about a Sony CDP-291 isn't it ? Sorry for the digressions.

So, I worked a bit on it.. took only a few minutes to declare it a write off.  This is the end of this repair...

Pulled the transport out of the loading mechanism, so I can get better access the PCB and things in general...

Checked power supplies, after having first removed one of the gears that drive the pickup, so the sledge motor can still turn yet the pickup is not self destructing anymore, banging/bouncing constantly against its stop.

- There is +5V for the digital decoder chip. That rail is spot on and next to zero ripple, perfect.

- Then there is +7V for the driver IC/motors, or so the schematic says on the connector pinout. But on the power board PCB it's marked as 8V. On the schematic, the test point on the driver IC reads 8.2V... and as for me, I measured 8.6V !  Quite a bit of ripple, 35mV (using non RMS DMM) of ripple, but given that the sledge motor was running, seems fine to me.


As Gyro suggested, I then checked the differential inputs corresponding to the sledge motor, pins 10 and 11. Given that the motor is turning full blast, I should therefore be able to measure a significant differential voltage between those two input pins. I didn't care about the ground referenced voltage on those individual pins, irrelevant, only the diff Voltage is relevant.  I measured.... a dead ZERO !

So yes, that driver IC is indeed faulty, powering the sledge motor full blast even though it's not being asked to do so.

But there is more !!!

I was playing around with the little flat flex cable that connects the pickup to the control board.... glad I did, was worth a look :

- On the control board side of the cable, looks weird : the contacts were clearly visible as if the cable had not been fully pushed in. Contacts look like there is come corrosion, and the contacts toward the center of the cable, look kinda damaged, half lifted from the plastic backing. I don't know, It just all looks very messy...

- On the other side of the cable, where it plugs to the pickup, that's even more entertaining : the cable this time looked fully inserted, no metal visible that I could see.... pulled the cable anyway and.... WHAT ?!  There is NO metal/contacts to be seen ! See pictures ! At first I thought wow, weird, maybe the cable broke and the contacts are still inside the connector or something... but no. There are no bits and pieces left stuck inside the connector, and when you look closely at the cable, you can clearly see that it was intentionally CUT by hand !  Edge was cut clean, it's not broken due to fatigue/stress. The edge is also not straight nor square. The contacts at the end of this cable have clearly been deliberately cut by someone !!   


So... end of repair. Driver IS is 20 euros shipped, a new cable for that pick-up is 10 euros or so IIRC (though I could maybe put the old one back into shape if I was desperate).... not worth the money nor my time... will keep it for parts.
Think I need to organize my pile of players a bit better. I should have several stacks :

- One for the players that wored out of the box, or that I have successfully repaired
- Another stack for fulty ones with an electrical failure
- Another stak for faulty ones with a mechanical failutre, waiting for a gear to be modeled and 3D printed.
- Another stack for worthless, hopeless POS , for parts only.


Will pull on of the micro switches from its front panel so I can fix the Toshiba....

Now going to report to the seller, he was so eager to kjnow the outcome ! I doubt he was the one who cut that flat flex, or else why would he ask me for news of the repair... unless he is some kind of weirdo, a psychopath of some sort ?! Hmmm....
Maybe his girlfriend tried to get it repaired without telling him, to offer that as a birthday present or something. Repair failed so she just kept silent....

[Gyro]

Yuk, messy.

That ribbon is single sided traces (the contacts just wrap around both sides), but the last photo looks like either a previous repair or extreme tin whisker growth (I think the latter). It would be worth clearing the shorts between the traces and trying it again.

[Vince]

It would be worth clearing the shorts between the traces and trying it again.

Uh ? As I said the other end of the cable has been cut... and the driver IC is kapput.

How will inserting just one end of the cable fix that ?!   

[Gyro]

Ah ok, I didn't understand that the images were different ends of the same cable, I thought they were opposite sides of the same end.

If you have confirmed the dead driver IC then there's nothing more to be done, economically.

[Vince]

Yep, that's the end for him !

That's good... now I can clear the bench and move on to more interesting players like that Radiola / CD371  for example ! 
Let's fix that one.... new thread coming up ! 

[Vince]

Seller got back to me. It becomes clearer now.... it was not his personal CD players, so he never used  and doesn't know anything about its history. Said he hates to to see old gear being dumped, so every now and then he buys a palette load, a big lot of old hifi gear, and tries to save them. He gives them a quick ride, sells those that can still work, and sells the defective ones for parts, lie the one I bought from him. So basically he just power it up, heard that horrible noise and that's about it. He knows squat about electronics so he didn't investigate anything, just listed for parts and that's it.

So, he is innocent, he didn't mess with the players, neither did his G/F ! LOL  Just bad luck.

Said he was interested in what the problem was as he would like to learn how to fix more of this stuff... but he doesn't even know the slightest thing about electrical or electronic stuff, so sadly the learning curve would not be economically viable for him ! 

Anyway, on to the next CD player...

[Vince]

OK, a month and 4 days later, I am revisiting this POS of a CD player... to give it a second chance.

Nothing this player did to convince me to change my mind about him, but rather a general movement recently where I decied to try harder to get my pile of unrepairable CD players.. repaired after all. Most of my players do'nt work, for one reason or another, kills me. I am trying to sell as many of them as possible to recoup some of the 300 Euros I poured into them, and I can only do that if I can fix as many of them as possible. It's ahrd enough to sell a working old players, so a parts unit is not even worth trying to sell, not worth the bother.

So I am trying hard to see how I could maybe rescue some of them which in my first pass I deemed hopeless.

Have already repaired the Philips CD824 which had a broken gear, because you can actually surprinsgly buy replacement gears these days, for a reasonable amount of money. That player will soon be for sale then.

As for the Sony CDP-291 discussed in this topic... I just had another look for this servo/motor driver IC that's kaput. somehow someone on Ebay is selliing his one much cheaper than the others, only 6,55 Euros shipped... at that price it's worth giving it a shot. Might be a dead chip of course, might be an alarm clock or egg timer chip in disguise (but so are all the other ones for sale...), you never know. But for 6,55 Euros I am willing to give a try, as it's the only hope this player has of resurrecting.

As for the damaged/vandalized pickup flat flex, it might be repairable, will give it a try. If that fails, I could try using another flat flex. It looks like a standard cable and I have salvage a few of these here and there. Of course I won't have the exact one I need, but if I find one that's too long, I think it might still work OK. As for width, looking how they are made, it seems it would be pretty straight forward to take a wider cable and slice it along with a sharp blade to make it the correct width/number of conductors. The appropriate cable Is available brand new, but way too expensive (10+ bucks IIRC) to make the repair economically viable, so it's not an option.

Anyway, will probably take a month or two for that chip to arrive from china, as always, so don't hold your breath....