On Wednesday, June 27, 2018 at 3:30:53 AM UTC-4, wrote:
On Friday, June 22, 2018 at 4:35:46 PM UTC-4, wrote:
This is my own receiver. Last year it started taking longer and longer for the protection relay to activate and turn on the speakers I finally took it out of service. I recall that it had no other problems that were evident. I had posted this problem at that time and I think that it was Chuck up in Canada who nailed it immediately. He recommended changing C6 on the protection board and .that resolved the protect relay problem. Now however there is another problem that I never had before. Most of the dial lights including the signal meter light are out and that meter also seems to be inoperative as well. I never had any trouble with any lighting or the signal meter on this receiver. This is a big quadrophonic receiver. The switching is done through the main selector switch and it's a nightmare to get to. A real rats nest. Does anyone who has worked on these recall any common problems with lighting on one of these? I suspect a ground problem because so many of these lamps are in parallel but it's so crowded in that area you can't see anything. I Really appreciate any help. Lenny

Chuck

First, thank you very much for the power supply jumper information. I hope that I will not have to use it but it is comforting to have it. The reason I say this is because in the interim I tried my Blue Stuff treatment. I sprayed the switch sections quite liberally and I really worked the switch through all of it's positions.

What I had previously written about the effect that Blue had on the intermittent phenoclic switches in the old tuners was not an overstatement. My display lamps are all on now and there is no smoke. I guess that I would say that I'm "cautiously optimistic" that I may actually have restored these tarnished contacts before they actually had a chance to burn.

I've turned the receiver on a few times now since the Blue Stuff treatment and and the display has come on strong without flickering each time. I guess we'll see.

Now I have to address the other problem with the non functioning signal meter. As I had said it always worked before and never caused a problem. But now it just lights up and does not indicate signal.

I really don't see how but could this be some crazy kind of coincidence, or perhaps something associated with the lighting system problem?

The tuner section of the schematic, F-1479-2A shows two meters and one small 6V 100ma lamp. Please correct me if I'm wrong but M705 looks like it could be the signal level meter and M706 looks like it is connected to the discriminator output for station centering. Then there is that small 6 volt 100ma. lamp which is connected off pin 12 of the board. Could that be the stereo lamp? To troubleshoot the signal level problem would M705 simply get a DC output off that HA1120 chip and through the transistor proportional to signal strength? Thanks for any further help. It is very much appreciated.
Lenny

IIRC, the Blue Stuff product contained an actual abrasive along with the blue schmutz carrier. If the abrasive scoured the contacts into working, I think I'd follow it up with a non residue cleaner to get the blue carrier off. I remember the blue carrier thickening into a stiff almost glue like consistency over time.