Studer A800 audio noise from PSU

[Pat Maki]

Update - Put in the 2N5884 but that didn't get me the +15V.....voltage took a slow nosedive to 0....so swapped the LM340KC and that brought the +15V back. Looks like problem solved. Found a couple brittle regulator wires

 

[Brian Roth]

For future reference...

Beware of all the Molexes hiding behind the audio cards. You have to "fold down" that entire front section to get to them (almost a 2-man job to do that because the assembly weighs a jillion pounds).

Yellow Frako(?) axial electrolytics on various audio cards. They tend to short.

Bri

 

[Walrus]

Yes, cleaning up those molexes is definitely a labour of love, as you have to remove all the cards then pull out all the rear connections before you can unscrew loads of screws to remove the motherboards.
All the while with the front section resting on your lap!
Yes, I have done it to a couple of machines!

 

[aurt]

One more "while you're in there" suggestion. C6 on the 810 card is a 100uF 35V axial lytic. It's in the circuit controlling the triacs that turn the power on or off. When it dries up it will cause the supply to power cycle at mains frequency, which makes an incredible commotion with the inrush current. Sounds like it's being dropped down the stairs. Worth considering if you've got it out.

 

[Pat Maki]

One more "while you're in there" suggestion. C6 on the 810 card is a 100uF 35V axial lytic. It's in the circuit controlling the triacs that turn the power on or off. When it dries up it will cause the supply to power cycle at mains frequency, which makes an incredible commotion with the inrush current. Sounds like it's being dropped down the stairs. Worth considering if you've got it out.

Thanks, yeah replaced all Frakos throughout with new Vishays.