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...when I turn the amp from standby to ON. Hum goes away when I pull out the rectifier tube. I've tried different rectifiers and it doesn't matter. Even swapped out all my tubes one by one, as well as replaced every component of the LTP one by one, and every component of the power supply one by one. I can sort of play through the amp, but the hum and another LOUD abrasive noise will not stop. Also have one output tube redplating. Any ideas?
thanks!

The hum is because the one tube is redplating for sure,but you need to find out what's causing the redplating.I assume you have isolated the problem to the one socket and have tried the usual stuff like new tubes and bias check.
What amp is it you are working with?
Something is causing the tube to draw the current.The most logical approach would be to trace all the wiring associated with that socket and measure all the resistors.

Thanks for the quilck reply, phsyconoodler.
The amp is a Lightning-ish 20 watter with 6v6's with a few of my own tweeks. Other than that, it's a fairly standard circuit.
I did notice that the cathode pin (on the socket with the redplating tube) is loose. Take out the tube and the pin sticks up out of the top, then it must be pushed back down. That's about the only anomaly I've noticed. I've measured all the resistors, and my voltages appear to be just fine. And like I said, I've replaced many components already, so if I gotta replace a socket it's definitely no biggie.
I appreciate any and all help and suggestions, everybody. Please keep 'em coming. I'll be on and off here all night (as usual) to converse about this. As far as working in the beast goes, well, I've probably put in close to 8 hours today, so I'm callin it quits til tomorrow. I will say this: what sound I was able to get out of this new build -- WHOA!!! Definitely "clip-worthy"

The cathode pin is loose?Well that's where the problem likely lies.

jimipage wrote: I did notice that the cathode pin (on the socket with the redplating tube) is loose. Take out the tube and the pin sticks up out of the top, then it must be pushed back down. That's about the only anomaly I've noticed.

referring to the pin on the socket, not the tube itself.
Never had a bad socket before. How often does that happen?
Could that be the cause of a problem like I'm getting?
Any other symptoms for a bad socket?

Hi,

jimipage wrote: Never had a bad socket before. How often does that happen?

Did you get a bulk deal on those new fangled Shuguang things? If so, my stock ended up with about 15% bad sockets

Good luck!

update:
I ended up replacing both output sockets, but the hum was still there.(just as well -- I noticed a faulty pin in the other socket, too) I started chopsticking around and it appears as if the probem is centered around the PI. Looks like I'll have to rewire everything from that socket to the board, maybe even end up replacing that socket, too. The good news is I was able to get rid of the hum and noise momentarily by way of the chopsticking, but the crap kept coming back. I was able to make it go completely away by removing the chassis from atop the cabinet and placing it on a stand nest to the cab. Seems the vibration was helping to set it off. This build sounds absolutely killer! Reminiscent of an Express and a Studio .22 -- no kidding

S2 had a similar problem recently with one tube red plating and it turned out to be an under board wire that had chaffed - might be worth checking.

Other than what you have already changed out have you swapped the coupling cap to that tube?

And while we've got your attention You were wiring up a pair of output jack sockets and I think you were going for one 4 Ohm and one 8 Ohm. Have you thought about using a heavy duty DPDT slide switch as a changeover, might give you more versatility. (Reason I've chosen DPDT is to bridge each pair of lugs, just for insurance. 4&8 Ohm OT leads to the outsides, the centre to the jack tips and common from the OT to the jack sleeves)

hi, Strat
I did read about s2's dilemma when that happened, so the first thing I did check was under the board. I was having shorting problems where there was a frozen drip of solder underneath and just "hairs" away from one of the OT mounting bolts, so it was arcing. I figured that was the only problem, but I was wrong. In the process I think I ended up shorting out the OT. Luckily I had a replacement, but only with one tap, so my 4ohm/8ohm situation is no longer an issue
And, yep, I've switched out every component from the PI to the output, so I'm very sure the parts themselves are not in question. I believe I will go ahead and replace the socket for the PI tube tomorrow. That may be a little bit overkill since I'm thinking it just needs to be rewired, but I find it much easier to go ahead and replace a socket rather than de-solder and all that.
And I know I've said this before, but I will definitely have to post clips when this beast is done. I tell ya, I'm really satisfied and pretty proud of it. The only bummer is that I made an incredible effort to make this build as cleanly and "pro" as possible, but as you know all that can quickly go out the window when you end up swapping out so many parts. Still looks pretty good, though, but not quite how I intended. Next time, huh?

update:
I replaced the PI tube socket and rewired everything -- problem solved! Sure was a lot of work to finally find the problem, but I learned quite a bit. Thanks for the help, fellas. Once I can find my way through the mess that is my shop/recording studio I have to get some clips posted