s_r

I've uploaded a few closeup pics here. All I can see is how much cleaner the solder joints of other people here are. I've since cleaned up the residue between the crees joints after seeing how obvious it is in picture.

Well, I thought JoaMats suggestion about it being the 1N4007 was right. I got a voltage going both ways on it on the non working board but only one way on the working one. However I replaced it and it shows the same behavior once in the board. I swapped out the LT1021 in case that had something to do with it but the same result (voltage shown in both directions). Faulty STN9360 maybe? I've also double checked the current limiting resistor and it's actually 5.1R.

I tried reflowing a number of joints around the 10m90s & the resistors around them. No change in behavior though. Also did some more measuring, the voltage across the 4.7kOhm resistor on both boards measure the same (about 1.77V). Pin 1 on the 10M90S right above the DN2540 reads +17V while pin 2 reads +559V, same as the cree. Not sure if those measurements are of much use though.

Nope, the same is true on the other PSU board which measures just fine. As for the cree, D reads +559V, while G reads +17V (referenced to ground).

It's definitely the 10V LT1021. I'll double check the voltages on the cree in a bit.

I've just recently gotten to where I can test the PSU boards, however there's something up with the +450V supply. I only get +14V out of it. I get 569V out of the bias line so I think I can rule out the bridge rectifiers not working. I suspect the steel screw for the cree fet may have shorted, so I've swapped it for a peek screw. No change in behavior though. Anything I should check out with a scope first before I try swapping out the cree? Excuse the blurry pic.

As in total volume. The relative amount of noise is probably unchanged, but it's too quiet to notice. The board I have has spots for the 5pf caps in parallel with the 100k resistors. As far as I can remember this is everything I've tried: -swapping tubes, power cables/plugs on the PSU to see if the noise would swap channels -trying different sets of input & output tubes -powering up one channel at a time -replacing the takman resistors in the battery with xicons -replacing the 10k pots in the battery with PTF56 resistors -adding a 1k resistor to the gate of the K216s -lowered the resistors in the PSU for the -500V supply -touch an insulated screwdriver to the trace between the ptf56 & k246 per 8street's suggestion

It's been the about the same amount of noise on both to start with. Swapping tubes, power cables, or powering up one channel at a time didn't change whether a particular channel had noise or not. Earlier one channel alone would be much quieter than the other powered up alone. Haven't tried that again after doing some part replacements though.

Yea, I wouldn't dare move the probe while the amp is still on. The problem is I have no idea where/how to start looking. What parts would be a likely culprit?

A Rigol DS1054Z, and these are the additional probes I got.

Figured I should get other opinions as well. Now that I have a scope on hand, where/how should I go about trying to track down the noise problem in my T2? I haven't tried poking around yet, since I don't want to risk blowing up the scope.

So after not doing anything with my T2 for a while, I'm considering buying a scope to try to track down the problem. Would this scope & HV probes be enough to find whatever is causing the noise?

For $2.50 I'll take 20 pieces as well.

They're all (raised) xicons. A scope might help pinpoint the problem but it's been years since I used one (and not with anything high voltage). As it stands right now it's just a heavy, expensive paperweight.

I've put in some 1k xicons in series with the K216 gates now. It hasn't solved the problem, but it appears to have helped somewhat. The noise on the left channel is noticeably quieter than on the right now. Guess it's time to grab some caps to put in parallel with the 22k xicons in the battery. edit: Actually I'm not sure it changed the noise at all. It's been a while since I listened longer than a minute to the T2 due to the noise.

Much like this then (pic is of Inu's T2)? Would all the 2SK216's need this or only Q5/Q6 & Q26/Q27? D'you happen to have a part number for the .1uf caps?

Wish I did. Although I really wouldn't want to chance blowing up someone elses scope.

I've tried this now, and got no audible change through headphones. I've also been waiting for a replacement set of input tubes, which I got the other day, to see if that cures the noise. Still there, however.

I used silicone thermal paste, specifically this stuff.

Yea, I ordered some 22ohm resistors to put in the -500V supply as well. I assume you mean touch the legs of the 10k PTF56 or the 2SK246 and not the point where it's soldered, right? Do you mean the noise would maximize in the other channels batteries, or in the other battery in the same channel? Either way it sounds like I'm looking for a change in the noise by touching these points.

So I've now been able to replace the 10k trimmers with PTF56 resistors. The batteries adjusted just fine too. However the background noise is still there. Could the PSU be the culprit somehow?

I'd check if the diodes didn't have a high enough wattage rating. The vishays I use are rated for 1.3W (some are 1.5W).

I bought my teflon octal sockets off ebay, pretty sure this is the same item.

I originally thought the left channel might not have all its LEDs lit or maybe the battery was out of whack, but it checks out fine. I also tried all the combinations under the sun and the channels don't swap their behavior. Going to order some parts to try and swap in, mainly some PTF56s to replace the 10k trimmers in the battery. Would 10pf work as something to try in place of the 5pf cap?

Swapped the input tubes, no change in each channels behavior when powered individually.