Test Equipment Anonymous (TEA) group therapy thread

[factory]

@Vince
Re Quad amp, what is the voltage of that suspected secondary winding supposed to be? It might not be shorted, there is a possible overload on the PCB as that is where the resistor is that has expired, I don't really see how a shorted secondary winding would cause the resistor to burn out as the winding is before the resistor surely? If you know what the voltage of the circuit rail that secondary was feeding, power it up using a bench supply in current limit mode and trace the voltage trail  to see if you can pinpoint the faulty item.

Those amps in working order are worth good money.

I'm sure he said he tried it with the secondary disconnected and it still blew the fuses. 

David

[Vince]

@Vince
Re Quad amp, what is the voltage of that suspected secondary winding supposed to be? It might not be shorted, there is a possible overload on the PCB as that is where the resistor is that has expired, I don't really see how a shorted secondary winding would cause the resistor to burn out as the winding is before the resistor surely? If you know what the voltage of the circuit rail that secondary was feeding, power it up using a bench supply in current limit mode and trace the voltage trail  to see if you can pinpoint the faulty item.

Those amps in working order are worth good money.

Spec, as I said that transformer blows the fuse even with the secondary winding DISconnected from the amp !

CAN'T YOU FREAKING READ !!!

Oh no please stay, I apologize, I didn't really mean to say that sorry ! 

You made me double check and turns out the tranny is not dead after all ?! I guess I was so fed up with this thing yesterday that I got a bit confused in the heat of the action, and jumped on conclusions too fast, because my brain had already decided to give up on this thing, I guess ?! 

So I just put the amp back onto the bench, shorted the fuse holder with crocodile clips because I am bored of blowing fuses, and powered the amp through my dim bulb tester. Again, secondary is disconnected, I pulled one of two secondary wires from the bridge rectifier.
Flicked the switch on the DBT.... light did not come on, and no explosion, and the "Power on" indicator light on the amp is lit ?! Hmmm...
I thought maybe it's safe to get closer to the amp now, might not explode in my face after all.
Grabbed the DMM and measured voltage at the secondary... 60V ! 

Schematic of the amp PSU section above.  60+ Vac, that's like 85V or so once rectified and filtered... and the two big filter caps are  rated at 100V.  Schematic says that the amp runs on 67V DC, so I guess 85V DC at the input of the voltage regulator board adds up nicely.

I love you my Spec, I really do, you made me doubt and double check !

So now I just need to fix the voltage regulator board, should be easy !

Thanks also to the gentleman who said that a sub-ohm resistance reading on the secondary could potentially be normal.... clearly it is ! 

Oh what would I do without my TEA buddies, thank you all ! 

OK so let's solder my 4 new snap-on caps back into this amp, and troubleshoot it yeah ! 

As for prices, I do'nt think I will get silly money for it. I just checked Ebay UK, QUAD's home land, and they are loads of them, between 250 and 500 IIRC... but the simple fact that there are so many at the same time probably means that... they just don't sell !
Checked Ebay France, not a single one for sale. Checked Leboncoin.fr which is the site most people use over here.... ah, some for sale. Again silly UK like prices, but all ads are old meaning they don't sell !

Me think that with the tough times we are living in recently, people are desperate for money and all the audio guys sell their vintage stuff to bring some money. So now is the worst time to sell this amp.... but I am not going to wait 3 years to sell it, I want it to leave my house ASAP.
So if I can fix it then I think I will advertise it at 250 Euros at first, and expect that I will have to drop a bit below 200 to get anyone interested...
Still, it's a lot of money for something I did not pay a cent for !

Then I also have the 33 pre-amp for sale and this one does work fine ! ... But it's missing one button and "dada" website are out of stock on most of these 33 buttons, my luck    Will google a bit to see if I can find one else where.

OK so let's troubleshoot that PSU board then, stay tuned ! 

[factory]

Back to the HP 5090 receiver 198kHz conversion board project, I fitted the remaining parts this afternoon, I tested the PSU section before fitting the rest of the ICs.



For testing I used the 1MHz output of the Racal counter for the 2kHz divider stage, fitted a random ferrite antenna (probably the wrong one for LW), the 2kHz is the only bit I had working, I suspect the antenna coil is a MW one, or there is too much interference due to it being evening when I tested this and all the RF noisy modern crap is swamping the signal. 





Need to try again during daylight hours.

The Radcom project my board is based on; https://archive.org/details/RadCom_Magazine_1989-11/page/n73/mode/2up

David

I finally posted the 5090A today, work being mad last week and the PO sunt without notice on Saturday conspired against me.

Thank you Robert.
A guess they might be short of staff? I had the same problem at another small shop last Friday.

Had a look at the radio service data DVD I have, it confirms what I thought last night, I was using the MW coil, the LW one has more turns (some Pye radio data gives the number of turns they used), will try again Wednesday afternoon.

David

[tautech]

@Vince
Re Quad amp, what is the voltage of that suspected secondary winding supposed to be? It might not be shorted, there is a possible overload on the PCB as that is where the resistor is that has expired, I don't really see how a shorted secondary winding would cause the resistor to burn out as the winding is before the resistor surely? If you know what the voltage of the circuit rail that secondary was feeding, power it up using a bench supply in current limit mode and trace the voltage trail  to see if you can pinpoint the faulty item.

Those amps in working order are worth good money.

Spec, as I said that transformer blows the fuse even with the secondary winding DISconnected from the amp !

CAN'T YOU FREAKING READ !!!

Oh no please stay, I apologize, I didn't really mean to say that sorry ! 

You made me double check and turns out the tranny is not dead after all ?! I guess I was so fed up with this thing yesterday that I got a bit confused in the heat of the action, and jumped on conclusions too fast, because my brain had already decided to give up on this thing, I guess ?! 

So I just put the amp back onto the bench, shorted the fuse holder with crocodile clips because I am bored of blowing fuses, and powered the amp through my dim bulb tester. Again, secondary is disconnected, I pulled one of two secondary wires from the bridge rectifier.
Flicked the switch on the DBT.... light did not come on, and no explosion, and the "Power on" indicator light on the amp is lit ?! Hmmm...
I thought maybe it's safe to get closer to the amp now, might not explode in my face after all.
Grabbed the DMM and measured voltage at the secondary... 60V ! 

Schematic of the amp PSU section above.  60+ Vac, that's like 85V or so once rectified and filtered... and the two big filter caps are  rated at 100V.  Schematic says that the amp runs on 67V DC, so I guess 85V DC at the input of the voltage regulator board adds up nicely.

I love you my Spec, I really do, you made me doubt and double check !

So now I just need to fix the voltage regulator board, should be easy !

Thanks also to the gentleman who said that a sub-ohm resistance reading on the secondary could potentially be normal.... clearly it is ! 

Oh what would I do without my TEA buddies, thank you all ! 

OK so let's solder my 4 new snap-on caps back into this amp, and troubleshoot it yeah ! 

As for prices, I do'nt think I will get silly money for it. I just checked Ebay UK, QUAD's home land, and they are loads of them, between 250 and 500 IIRC... but the simple fact that there are so many at the same time probably means that... they just don't sell !
Checked Ebay France, not a single one for sale. Checked Leboncoin.fr which is the site most people use over here.... ah, some for sale. Again silly UK like prices, but all ads are old meaning they don't sell !

Me think that with the tough times we are living in recently, people are desperate for money and all the audio guys sell their vintage stuff to bring some money. So now is the worst time to sell this amp.... but I am not going to wait 3 years to sell it, I want it to leave my house ASAP.
So if I can fix it then I think I will advertise it at 250 Euros at first, and expect that I will have to drop a bit below 200 to get anyone interested...
Still, it's a lot of money for something I did not pay a cent for !

Then I also have the 33 pre-amp for sale and this one does work fine ! ... But it's missing one button and "dada" website are out of stock on most of these 33 buttons, my luck    Will google a bit to see if I can find one else where.

OK so let's troubleshoot that PSU board then, stay tuned ! 

I was hoping you'd get a reality check and revisit your work on this amp. Stuffed mains transformers are quite rare, especially in better quality gear.

As for secondary side measurements of LV high current windings, of course they will read very low Ohms.....pull some apart and discover why. 

[Specmaster]

@Vince  I love you too man 

There you go, the secondary side will nearly always have a far lower resistance than the primary because it will have considerably fewer windings, hence why I said to power the amp from an external power supply and double check. As to the prices, it all depends on how desperate you are to part with it, if not in a hurry, it would be best to match or maybe very slightly undercut the prices, while making sure that your presentation of the equipment is second to none, so it stands out head and shoulders above the competition. If you are really keen to part with it, I'd price it about 25% lower than the rest and see what happens.

[Vince]

Not that desperate.... if it works and I can get decent money for it, it's worth waiting a few weeks or 2/3 months I guess.
.. but not a year for sure.

Yes the ads I saw are appalling, won't be difficult to do better.

I remember one saying in the very title of the ad " GOOD CAPS "... then when you read the full description, what he really meant was " The x4 60 year old can caps are still in place but I had a quick look at them and they are not bulged and no crusty stuff on their bottom, so surely they must be good !! "...... 

Then another seller that said he DID replace these big can caps.... but go figure, fails to show any picture of the inside of the amp, saying "forgot to take a pic, will post it tomorrow"... yeah right... 

If I can fix the power amp, then I will be able to sell the preamp + power amp PAIR, as a set, and this is it looks, more appealing, more valuable. Especially since I have both vintage power cables to wire them up. I just need to make a 4 pin DIN cable to connect the output of the pre-amp to the input of the power amp.... I have ordered a couple connectors to this effect, in my recent big Farnell order... but guess what ? Despite receiving 3 different parcels for that one single order.... there is still ONE missing item.... yeah, these DIN connectors/plugs ! 
I hope they will think of sending them to me and that I won't have to fight with them for weeks to get them... 


OK so I worked on that PSU

1) First I wired one single filter cap straight to the output of the bridge rectifier, with nothing else connected downstream. Just the bridge and one cap.
No explosion followed, and I got the expected 85Vdc across the cap, good !    So now I could move on to working on the regulation board.

2) The schematic does not match the board !    Yes, there are two schematics, I did pick the correct one for my serial number, but in this case it does not matter because the components I was interested in, were the same in both versions.

3) The PCB is of the shittiest quality I have seen... looks exactly the same as my Rochar Neeksee DVM : brown board, and pads that lift as soon as you dare pointing a soldering at them ! 

4) The diode (not the zener, the other one) was not obvious to find (had to follow traces to figure it out for sure), as it looks 100% like a tiny 1/8 resistor ! With a blue body with rounded ends, and colour bands ! 

5) The resistor that smoked... the paint is chipped in the middle so I can only read the first colour band. Looks like either blue or maybe grey possibly. So either 6.8K or 8.2K. But the schematic says it should be 10K      So I guess it's not critical and anything between 5 and 10K should bring it to life. It reads in this window so clearly it didn't smoke enough to fail completely, still usable. So I put it back on the board and will test the amp like that at first, should be good enough.

6) Then tested both diodes, look OK

7) Tested both transistors, an NPN and a PNP... they buzz alright as well.

All resistors read OK.

9) The big 2.2uF film cap reads OK as well..

10).... so.... if everything is good, or good enough, on this board... what could be wrong ? Only thing left is the big pass transistor mounted on the heat sink at the back of the amp, along with two other power transistors for each channel / speaker output.

So I test this puppy and... both junctions look OK, 0.45V or something, a bit low but I expect that when testing power junctions with only 1mA of current from the DMM, so it didn't worry me. However when I buzz collector-emitter, in either direction.... dead short !

Which means it sent 85Vdc to the amp boards instead of 67V    I hope it did not blow anything in this area...

So I need to replace that pass transistor... but it's impossible to get to as is. It's 100% inaccessible, can barely see it with a torch light. It's in the middle of the heat sink, and right behind the mains transformer.
To get to that transistor I will need I think to part the heat sink from the chassis.... but it's 23H30 here so I need to go to bed, I will look into that tomorrow !

Parts list says it's a " 16112 " ! Doesn't sound like a transistor part number eh ?! 
Never mind, it's a TO3 NPN so I will just stick a 2N3055 in there and see what happens ! 
Have a load of them so need to use them for something eh ! 

 

[BU508A]

Yay! The 74HCT4158 chips sent by BU508A for my Tek AFG5101 Option 01 board just arrived today! 

 
Took only ca. fifteen days from .de to .jp - much faster than last time.   

Big thanks to BU508A, now I can measure a baseline for this circuit and then see how it behaves when I swap the HCT series chips for non-TTL HC series chips to see if it'll still work.
Fingers crossed it does, as the HC series are still available but the HCT seem to be obsolete everywhere... (hence the help from BU508A in sourcing them).

You are welcome.

[TERRA Operative]

HOORAY! Vince will yet slay that beast! More money for the TDS scope fund!

It seems God is in his heaven, all is right with the world.

[BU508A]

Fingers crossed it does, as the HC series are still available but the HCT seem to be obsolete everywhere... (hence the help from BU508A in sourcing them).

Just out of curiousity I did a search again on goolge and found this:
https://www.kashinoki.shop/?pid=148344158

[Rhine_Labs]

Pulled the SDS1104 off the Shelf Replaced it with a SDS2104X Plus and it Almost did not fit.. Not sure of I am going to off it or put it up for a 2nd unit.

Hope to have other bench finished by the first of the year.

[tautech]

Pulled the SDS1104 off the Shelf Replaced it with a SDS2104X Plus and it Almost did not fit.. Not sure of I am going to off it or put it up for a 2nd unit.

Hope you have other bench finished by the first of the year.

LOL, wondered if you were able to shoehorn it into where the X-E was. 

Have you installed a wireless mouse into the SA and DSO ? Recommend you do at least in the scope.
Do you have a workstation close so to be able to use their webservers for remote control and direct capture of screenshots ?

[Rhine_Labs]

Pulled the SDS1104 off the Shelf Replaced it with a SDS2104X Plus and it Almost did not fit.. Not sure of I am going to off it or put it up for a 2nd unit.

Hope you have other bench finished by the first of the year.

LOL, wondered if you were able to shoehorn it into where the X-E was. 

Have you installed a wireless mouse into the SA and DSO ? Recommend you do at least in the scope.
Do you have a workstation close so to be able to use their webservers for remote control and direct capture of screenshots ?

I have a not hooked a wireless mouse up yet. I have a PC Available nearby. I Just unboxed the scope and put it in place and took a photo! I am Uploading the Unboxing to youtube as I am typing this YT UL is slow.

[tautech]

LOL, wondered if you were able to shoehorn it into where the X-E was. 

Have you installed a wireless mouse into the SA and DSO ? Recommend you do at least in the scope.
Do you have a workstation close so to be able to use their webservers for remote control and direct capture of screenshots ?

I have a not hooked a wireless mouse up yet. I have a PC Available nearby. I Just unboxed the scope and put it in place and took a photo! I am Uploading the Unboxing to youtube as I am typing this YT UL is slow.

Did you previously remote control the X-E ?
These X Plus have a few more features including a File Manager tucked away in the Save/Recall menu.
Is getting a LAN cable to them possible ?

[Rhine_Labs]

LOL, wondered if you were able to shoehorn it into where the X-E was. 

Have you installed a wireless mouse into the SA and DSO ? Recommend you do at least in the scope.
Do you have a workstation close so to be able to use their webservers for remote control and direct capture of screenshots ?

I have a not hooked a wireless mouse up yet. I have a PC Available nearby. I Just unboxed the scope and put it in place and took a photo! I am Uploading the Unboxing to youtube as I am typing this YT UL is slow.

Did you previously remote control the X-E ?
These X Plus have a few more features including a File Manager tucked away in the Save/Recall menu.
Is getting a LAN cable to them possible ?

Yea, Its on the network will try and play with it some in the afternoon tomorrow.

[tautech]

LOL, wondered if you were able to shoehorn it into where the X-E was. 

Have you installed a wireless mouse into the SA and DSO ? Recommend you do at least in the scope.
Do you have a workstation close so to be able to use their webservers for remote control and direct capture of screenshots ?

I have a not hooked a wireless mouse up yet. I have a PC Available nearby. I Just unboxed the scope and put it in place and took a photo! I am Uploading the Unboxing to youtube as I am typing this YT UL is slow.

Did you previously remote control the X-E ?
These X Plus have a few more features including a File Manager tucked away in the Save/Recall menu.
Is getting a LAN cable to them possible ?

Yea, Its on the network will try and play with it some in the afternoon tomorrow.

Have fun. 

[Robert763]

<SNIP>

10).... so.... if everything is good, or good enough, on this board... what could be wrong ? Only thing left is the big pass transistor mounted on the heat sink at the back of the amp, along with two other power transistors for each channel / speaker output.

So I test this puppy and... both junctions look OK, 0.45V or something, a bit low but I expect that when testing power junctions with only 1mA of current from the DMM, so it didn't worry me. However when I buzz collector-emitter, in either direction.... dead short !

Which means it sent 85Vdc to the amp boards instead of 67V    I hope it did not blow anything in this area...

So I need to replace that pass transistor... but it's impossible to get to as is. It's 100% inaccessible, can barely see it with a torch light. It's in the middle of the heat sink, and right behind the mains transformer.
To get to that transistor I will need I think to part the heat sink from the chassis.... but it's 23H30 here so I need to go to bed, I will look into that tomorrow !

Parts list says it's a " 16112 " ! Doesn't sound like a transistor part number eh ?! 
Never mind, it's a TO3 NPN so I will just stick a 2N3055 in there and see what happens ! 
Have a load of them so need to use them for something eh ! 

 

Hi Vince,
No DON'T put a 2N3055 in there  Vce is only 70V so well out of spec at turn on. 
I'm sure you have something better in your stash.

[TERRA Operative]

Fingers crossed it does, as the HC series are still available but the HCT seem to be obsolete everywhere... (hence the help from BU508A in sourcing them).

Just out of curiousity I did a search again on goolge and found this:
https://www.kashinoki.shop/?pid=148344158

Fkn lol, it's near a train station directly on my way to work... I can literally stop off on my way in.

It never came up in my searches, damn Google and the 'search bubbles'.......

I might just stock up a bit, just out of spite.

[m k]

Parts list says it's a " 16112 " ! Doesn't sound like a transistor part number eh ?! 
Never mind, it's a TO3 NPN so I will just stick a 2N3055 in there and see what happens ! 
Have a load of them so need to use them for something eh ! 

One supplement is offering 40411(90V) as a replacement for 16012.
MJ802 is also mentioned elsewhere.

A side note for a possible bystander,
since rectifier diode packages are not symmetrical there are two physical versions.

[Vince]

<SNIP>

So I need to replace that pass transistor... but it's impossible to get to as is. It's 100% inaccessible, can barely see it with a torch light. It's in the middle of the heat sink, and right behind the mains transformer.
To get to that transistor I will need I think to part the heat sink from the chassis.... but it's 23H30 here so I need to go to bed, I will look into that tomorrow !

Parts list says it's a " 16112 " ! Doesn't sound like a transistor part number eh ?! 
Never mind, it's a TO3 NPN so I will just stick a 2N3055 in there and see what happens ! 
Have a load of them so need to use them for something eh ! 

 

Hi Vince,
No DON'T put a 2N3055 in there  Vce is only 70V so well out of spec at turn on. 
I'm sure you have something better in your stash.

Good point, thanks  ! 

I can't find a datasheet for the original RCA "16112" tranny, but yes as you said... we need at least 85V for Vce.
As for current, the manual says the amp draws maximum 200Watts. So with a 67V supply in the thing, that means 3A.

So we need more than 85V and 3A for it to survive.

Here is what I have in stock in TO3 packages that satisfy these voltage and current requirements, according to the spreadsheet fairy :



I think I could try a 2N4347 or a BU412 ?

I will try that and report...

[BU508A]

Fkn lol, it's near a train station directly on my way to work... I can literally stop off on my way in.

It never came up in my searches, damn Google and the 'search bubbles'.......

I think, when I did my first search, it did not show up either.
Maybe the offer was going online afterwards or I have used a different search pattern.
I've found it with: "74HCT4518 shop" without the double quotes.

[Ice-Tea]

Somebody was cured by TEA and finally decided to get rid of everything, enjoy:

https://www.ebay-kleinanzeigen.de/s-bestandsliste.html?userId=87101374

(Germanians mostly  )

Cheers,
DC1MC

He's being a bit optimistic with his prices don't you think?

McBryce.

Overly optimistic on some things I say, barely acceptable on others, but these are starting prices, so if one is interest doesn't cost too much to drop an inquiry.
I'm preparing to do the same, it seems that I will only afford in near future something like a suitcase laboratory, but I don't think that someone will come to Mannheim to get my stuff in a Transporter. And my prices are rock bottom, "just get it and do something with it, if you sell it keep 30% of the profit and send me the rest to be able to feed my cat". Not many takers, even if actually I have some reasonable quality stuff, mostly working as intended.

 Cheers,
 DC1MC

All in all, his prices don't seem that out of this world. But they're the prices you might expect to get after a while if you're patient. Which is also the reason why most of you lot don't shop with me.

Damn bargain bassement hunters 

[Vince]

QUAD 303 AMP REPAIR

I just replaced the pass transistor, with a 2N4347.
The heat sink assembly actually comes off extremely easily, it's well designed. Just a couple screws on each side of the chassis and that's all.

So I soldered my 4 big snap-in caps... again, which is a huge pain, their terminals just are not made for that kind of wiring. So it's butchery for the most part... but the electrons can flow none the less so I don't think they care too much.

So I fired the amp up, again through the dim bulb tester of course and..... the light bulb lights up very bright and solid. This amp still has a massive short.

Maybe the push-pull trannies ?!

I know squat about amps, but I have the schematic so hopefully I should be able to figure it out....stay tuned.

But that will be tomorrow's next installment.

 

[Specmaster]

Of course you'll manage it Vince, amps are pretty easy compared to most other things, there are coils to trim etc, no tunes circuits etc, just take your time, keep cool and think clearly, don't get frustrated, think logically and you will get there. 

[Robert763]

QUAD 303 AMP REPAIR

I just replaced the pass transistor, with a 2N4347.
The heat sink assembly actually comes off extremely easily, it's well designed. Just a couple screws on each side of the chassis and that's all.

So I soldered my 4 big snap-in caps... again, which is a huge pain, their terminals just are not made for that kind of wiring. So it's butchery for the most part... but the electrons can flow none the less so I don't think they care too much.

So I fired the amp up, again through the dim bulb tester of course and..... the light bulb lights up very bright and solid. This amp still has a massive short.

Maybe the push-pull trannies ?!

I know squat about amps, but I have the schematic so hopefully I should be able to figure it out....stay tuned.

But that will be tomorrow's next installment.

 

Have you measured the resitance across the power rails with a DMM? Power off of course and using both normal resistance and diode test mode?
If a short is shown tracking it down power off is easier and safer.

[Ice-Tea]

Accidently listed a TDS 3064B for 12€.