My Revox B 760 tuner fix up project

[beels]

W1jim - thanks so much for this thread! I had a similar issue with my B760 and was able to fix it using your experience and part selection. In my case, it was the ones digit in the frequency display that was misbehaving -- it would only show either a 0, 4, 8, E, or c. The ICs were the same, so I replaced IC2 (9317BPC) on the Display Board with an SN74LS47. My ICs are actually socketed already, which is different than yours.

Now I just need a new Signal Strength meter. Tried banging on it a little, but looks like my indicator needle is actually loose inside and flopping around.

 

[w1jim]

Glad you were able to capitalize on my tinkering.

 

[w1jim]

Update.
I was playing around with the B 760 and noticed a smell - it was plugged in but not turned on.
I found that the 0.1uf/250v capacitor mounted to the back of the voltage selector and paralleled with the AC power cord was the culprit. I could see inside it’s transparent case where it was shorted.
I replaced it with the brown capacitor in the picture.
I had to dismount the transformer to get some maneuvering room.

 

[amptramp]

If you look down this list from item 17 to 19, you will find X1, X2 (line-to-line) and Y2 (line-to-ground) capacitors that are designed for service as safety capacitors and interference suppressors on the plug side of the power transformer. They are guaranteed to fail open if they fail at all. They should be used for all input filters and bypasses:

https://justradios.com/capacitors.html

I have some other justradios capacitors in a box behind me and I can vouch for the quality. The proprietor, Dave Cantelon, is a member of the London Vintage Radio Club in London, Ontario, Canada, as am I, and he is well respected in the antique radio restoration business.

High Voltage Electrolytic and Film Capacitors for Tube Radios (justradios.com)