Advice on Parabee and failing C4S

[banjopicker]

There's a loose connection in the amp.  Physically moving it restores the connection, then the amp goes back to working.

The way I set up the amp for testing I think this is only likely if it is that joint on the C4S itself. The amp was secure, still and stable and had not moved for some time as I allowed it to stabilize electrically as well. With the lightest possible touch of the probe to the copper wire going into the "I" (imagine me playing the buzzer game "Operation")--which didn't move the board at all much less any of the rest of the amp's wiring--the second LED lit and stay lit. It was almost like I reset the C4S by quickly shorting it to ground.

On a previous diagnostic attempt when it wasn't working, I had aggressively poked around everywhere in the amp with a chopstick to see if I could locate any bad connections and it made no difference. I have also moved the amp in the car several times while I have been troubleshooting it and it never affected its behavior. So the multimeter probe resetting it may be a red herring, but at a minimum, even if it is a bad connection, at least it narrows the location further. I will wait to reflow joints until I can isolate the actual culprit so I don't screw up the diagnostics or the amp, and will report back if I make any progress.

Thanks again.

[Paul Birkeland]

That old magnet wire we provided is good sounding wire, but this kind of issue isn't all that surprising with how challenging that stuff is to solder.  I think the good news for you is that you probably don't need to replace anything, but it would be a good idea to get out the soldering iron and reflow some joints!

[banjopicker]

An unfortunate update on the amp.

I made no permanent changes because for a long time I was able to "reset" the c4s by shorting its ground quickly while it was live, and it would then work again (go from one lit LED without sound to two lit LEDs with sound), for longer and longer periods of time--first days and then weeks. Poking it physically didn't seem to do anything, but that doesn't mean it wasn't a physical problem, because my short circuit may have been bypassing a bad physical connection.

Usually there was no drama with any of this though it is clearly ill-advised (I am in no way defending this dangerous and haphazard troubleshooting--I was just doing what, by accident, I found worked). Over a week ago I did this and there was an unusual electrical pop, but it still reset and played perfectly until today. Today the amp went out so I tried to reset it as usual but there was a big pop and the whole c4s went dark (tubes still lit). So assuming the problem was always in the C4S or its connection, I need to repair the C4s now, probably restuff it with new components. Assuming that the problem is in the C4S and not further upstream, that will hopefully do the trick permanently.

Anything I should look out for as I proceed or tips on rebuilding the C4S? Any particular maintenance suggestions for these units while I have the patient open on the table?

Thank you,
Stephen

[Paul Birkeland]

You still haven't actually diagnosed what's going on.

If the connections to the C4S board are loose, resolder them and call it good.

If you pull the board out and replace all the components, you could possibly just make new problems.

[banjopicker]

Fair enough.

Thanks,
Stephen