Golden Age PRE-73 broken - need some help pls

[DIY Daniel]

Hello guys, I had a pair of GA Pre-73 working for a while. Now one unit is broken I guess. The signal (Mic or Line) is very quiet and I get only 11V at the measure point on the pcb.
The Output of the powersupply is 24V seems ok.
If someone got an Idea to make it run again would be great. Thanks a lot!

 

[gyraf]

Check tantalum caps (in supply lines) for shorts?

 

[DIY Daniel]

I checked the tantalum caps, no shorts. Even swapped some electrolytic caps but no success. I noticed the 270ohm 5W getting very hot so the caps around will suffer. Thank you for your help gyraf and btw. thx a lot for the pultec and gssl I love em

 

[Voyager10]

Hi. On your photo I couldn't see any wires which appear to connect ground between the power supply (top left) and the main amp board.

I'm guessing, therefore, that circuit ground goes via the chassis - i.e. mounting screws for the PCB make contact between a contact area on the PCB and the stand-offs in the chassis.

If so, you won't be getting any meaningful voltage readings while the board is unscrewed like that, so you'll need to fix it back in before re-measuring.

Poor ground might be your original problem, so it's worth giving all the fixings a clean & screw them up tight to see if that helps.

 

[DIY Daniel]

@Vayager10 Thank you for your advice you are absolutly right. I always tested the circuit fixed with all screws otherwise you got no correct ground. Yesterday I swapped the 2n3055 but same result. I even tried to contact Golden Age but they ccd me to a local distributor and never heard something again .

My last try is to replace all the tantals back to electrolyths.

 

[Voyager10]

That seems a lot of effort, it might be worth a little investigation first.

There should be a direct connection between +24v on the power supply and +24v on those resistors. You should be able to trace this through with a meter with a continuity test range.

 

[guitarous]

@Vayager10 Thank you for your advice you are absolutly right. I always tested the circuit fixed with all screws otherwise you got no correct ground. Yesterday I swapped the 2n3055 but same result. I even tried to contact Golden Age but they ccd me to a local distributor and never heard something again .

My last try is to replace all the tantals back to electrolyths.

Did you replace the tantals for electrolyths? I'm having a similar issue with no luck so far.