New Crack "died" after 5 minutes of working great. How to revive?

[TubeNoober55]

Last evening, I got done putting my Crack together, and after some resoldering to get every resistance test to pass, I got every voltage test passed as well.  I set it up with some RCA cables, turned it on again, and plugged in a cheap headset with a 3.5 to 1/4" adapter, one that I wouldn't miss.  It sounded excellent, way better than I had imagined that headset could sound!  However, that wasn't to last, because after it being on  for about 5 minutes (3 minutes of listening), the volume suddenly faded out.  I checked the cables and tuned it off and on again, but still, no sound.  The only odd thing I heard was a moderate volume "thump" sound maybe a minute before it "died."  I unplugged it and left it for the night.

So, first question: Where would be a good place to start reviving it?  I attached some photos, so feel free to roast away! It's my first time doing a project like this, so there are probably a ton of nits to pick.

Also, I have another question about how to handle power left in the circuit.  I ask because after I flipped it over to take pictures, I trimmed a few leads back, and as my wirecutter touched one of the capacitor leads, it gave off a medium volume "pop" sound and a tiny spark.  No smoke or anything, but it is concerning. Would that cap be dead now?  But more importantly, if the circuit can hold onto that kind of power for ~18 hours after being powered, how exactly do I actually fix it without getting zapped or breaking everything?

[Paul Birkeland]

You would want to start with a voltage check before really doing anything else.  If the B+ isn't bleeding out of the circuit, that is something that could be indicative of an issue on its own, but we need quantitative information.  Are the tubes glowing when you turn the power on? Is the fuse blown?

As far as your build goes:


1.  The green wire going to A4/A5 cannot have that much of the jacket stripped off.  If that wire touches the chassis plate, you'll toast the power transformer.  The wire going to A9 looks to have the same issue.
2.  All of the lower terminals on your front terminal strip haven't been heated enough for the solder to flow properly.
3.  The wire to A7 has too much jacket stripped off.  If that extra exposed section of wire touches anything around it, your amp can be damaged.
4.  The solder joint at A1 is a cold joint.
5.  On the upper terminals on the front terminal strip, when something is to be "attached", you need to wrap the stripped wire or component lead up and around the terminal strip so it stays place.  If you just pass these through the terminal and expect the solder to hold them, you'll end up with an unreliable amp.
6.  The wire passing through B1 needs to be bent up so it doesn't touch B2.  If it touches B2, bad things will happen.
7.  The wires going to B3, B4, and B5 have too much jacket stripped off and they could short out to neighboring pins or the socket retainer ring.
8.  The green wire going to B8 has too much jacket off and could short out to a neighboring wire or socket terminal.
9.  12L and 20U have not be heated enough for solder to flow properly.
10.  21U is another place where the leads need to be bent over the top of the terminal so they stay put before soldering.
11.  The safety ground lug does not look adequately soldered.

[Drew1d]

Is your 12au7 wiring good?  make sure nothing is touching that shouldn't.