Studer 169 Master Module Recap

Hi guys! I'm restoring a  Studer 169 and now I'm replacing all tantalum and electrolytic caps on the master modules. I've removed all the caps from the pcb and I've got a big doubt about how to place the polarity of the 1000uf 16v  axial caps (C97 and C98). If i follow the service book polarity on the axial caps should be  placed in the same way ( positive on the top to negative on the bottom). I attach the picture. The problem  is that right now I don't remember how mines where placed on the pcb but I'm sure that both caps  weren't placed in the same polarity direction. That is confirmed when I've checked other user master boards like roginator's thread. My question is that if I should follow the manual?  Or its a mistake from the book and I'll have fireworks inside the Studer? Maybe  polarity in this case is not that important? (Maybe that's a dumb question, sorry but I'm newbie).

Thanks! All the best

Joan

Shakusky said:

My question is that if I should follow the manual?

Click to expand...

You are right, C98 is backward in manual.

Maybe  polarity in this case is not that important?

Click to expand...

It is.

moamps said:

You are right, C98 is backward in manual. It is.

Click to expand...

Great! Thank you so much!!!

The junction of those two goes to R99. In the attached schematic snippet you can see the +ve of C97 goes to this point (up) and the negative of C98 goes to the same point so it should be fitted +ve down.

Cheers

Ian

ruffrecords said:

The junction of those two goes to R99. In the attached schematic snippet you can see the +ve of C97 goes to this point (up) and the negative of C98 goes to the same point so it should be fitted +ve down.

Cheers

Ian

Click to expand...

Thanks for the info Ian!!

Hi

I'm after the party...anyway , I confirm C98 is backward in the Studer layout at service manual !!!
not usual for studer but it happen...
This post remind me something so I just double check in my Studer 169/269 red binder, an I find my hand writing correction at this service manual page/section

side note: when recaping (or any major component change) take a pict of the pcb BEFORE, so when in doubt you have the original state to check  8)

IIRC it's exactly how I find this mistake 6 or 7 years ago when recapping/restoring a "large" 369

Best
Zam

zamproject said:

Hi

I'm after the party...anyway , I confirm C98 is backward in the Studer layout at service manual !!!
not usual for studer but it happen...
This post remind me something so I just double check in my Studer 169/269 red binder, an I find my hand writing correction at this service manual page/section

side note: when recaping (or any major component change) take a pict of the pcb BEFORE, so when in doubt you have the original state to check  8)

IIRC it's exactly how I find this mistake 6 or 7 years ago when recapping/restoring a "large" 369

Best
Zam

Click to expand...

Thanks Zamproject.  Will do for sure!

One side question, taking advantage of  the  wisdom of this forum!  I'm planning to replace 4,7K Trimpot on input modules in order to calibrate them.  I'm  thinking about putting a Bourns Multiturn potenciomenter (took the idea from Roginators post). The issue is that old trimpots have only two pin, and the bourns has three pin. User user 37518 said in that same post that its possible to solder the middle tip to one of the other tips. is that right?

Again, thank you so much! I was close to have some fireworks inside the Studer!

Finally I've recapped master modules with mixed luck. One works like a charm and the other one doesn't work at all. Before the recap the module was working except the limiter  :'(.  Unfortunately I broke the path between C2 and C3 but I connected them trough a tiny  wire and checked there  was continuity with a multimeter, so i guess that's not the problem

Now VU doesn't move (only slihgty when I turn it on and off).

- I've fully recapped master module with high quality electrolytic and tantalum caps
- I've swapped IC1 from the working master channel  with no luck.
- Doesn't work when I turn on PFL switch, only vu moves slightly and I can only hear pops when I activate/deactivate pfl switch
- Doesn't send anything from insert jack
- No Identify signal, but it doesn't work with the other master channel because I still haven't recapped  monitor module (the Studer was in very bad shape)
- I'm building an extension card but I still haven't got finished yet, can i do the measuring with one or I will necessarily need three cards?

Could anyone give any advice, where I should start looking? I'll really appreciate it.

All the best.


Joan

I attach the master module schematic

Shakusky said:

...- I'm building an extension card but I still haven't got finished yet, can i do the measuring with one or I will necessarily need three cards?

Click to expand...

IMO, you need only PP2 connector/card fitted. Apply the line signal to hi-line input and trace it through the module.

moamps said:

IMO, you need only PP2 connector/card fitted. Apply the line signal to hi-line input and trace it through the module.

Click to expand...

Thanks for your reply.  Once I finish the extender card I'll check it out.

While I’m waiting for the extender parts to arrive. I’ve fixed one broken path, and I’ve been checking some points and now the situation is this:

1 - Fixed the mixer oscillator and the master channel receives signal from ident.

2 - Checked insert point on module: send doesn’t send signal , the return works perfectly.

3- Pfl on master works

4 - When Send signal post fader to master channels, and raise the fader I can hear sound but it interrupts with constant pops in exact very short periods of time.

5- swapped IC1 and nothing changes

Could be the transistors?? I believe I’m getting close.

Any help is really appreciated! Thanks!