Back again...problems with fading to black

[anthonynchandler]

Without too much surprise my Moreplay build is slowly giving up the ghost almost immediately after I ordered the upgrade! Bah ha ha.
It had been playing so well and then it started fading, but a hard tap to the volume knob brings it back, then after 30 seconds another fade into distortion and low volume.
I imagine it is a dead solder joint, but I redid the ones on the volume and a few others to no avail.
I expect it is better to fix it before the upgrade, but then the naive hopeful part of me pretends that the upgrade will take the bad solder joint out of the circuit!

How might I start to troubleshoot?

Many thanks, as always!

[Paul Birkeland]

Hitting the chassis disturbs all of the solder joints.  If both channels are fading out, this indicates the problem is not with the volume pot. 

When the sound fades out, do the tubes keep glowing? 

Generally it's very easy to just reheat all of your joints rather than spending too much time to find the one that's giving you troubles.

[anthonynchandler]

Thanks, Paul.
Yeahhh, I figured a reheat of all the joints will work best, and then see.
The tubes stay aglow before and during the fading. The problem is with both channels, all inputs and outputs.

I will check later this week as I seem to have come down with strep throat!

[anthonynchandler]

Strep throat is gone, so I am looking at the Moreplay again. As I was just about to redo the solder joints to rectify the fade to distortion I noticed one of the smaller brown capacitors has the beginnings of a bulge. While I doubt that relates to the fading, is that something I should replace asap? If I do I assume I should have to matching ones?

Any thoughts are always welcome.

Anthony

[Thermioniclife]

Yeah I Would replace and double check for proper polarity.

[anthonynchandler]

Sounds like a plan!

[Doc B.]

You also have a film cap that has a blob of solder on it. If that has melted thru the outer plastic coating you could have a shorted cap. If it just pops off and the plastic underneath looks OK it is fine.

[Paul Birkeland]

Once you have completed replacing that cap, please check the DC voltage at the junction between those two caps and report it here.  It is extremely rare for this kind of failure to occur, and it's possible that one of the 270K balancing resistors isn't well connected, which is causing too much voltage to appear across that cap.