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s_r

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About s_r

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  1. The ultimate DIY? A Stax SRM-T2!

    It's a good thing I have a decent hakko desoldering gun then. I'll take your word for it, but I'm just worried about taking the pads with it as I lift the RK50 off.
  2. The ultimate DIY? A Stax SRM-T2!

    I wish I knew. I've since tried removing the thermal paste from all the sand on the right channel in case it was shorting somewhere. No change though. Next thing I could try is putting .1uF bypass caps on the voltage set resistors in the PSU. If that doesn't do anything my next WAG is the RK50 being responsible somehow. Desoldering the RK50 seems like it'd be a huge headache, and a risk to damaging the solder points (the pins were a snug fit even before soldering them in).
  3. Where did you source the high voltage wire from? Probably won't be starting a circlotron build myself all that soon but it'd be nice to have beforehand.
  4. The ultimate DIY? A Stax SRM-T2!

    As I suspected, the sporadic noise hasn't actually gone for good. I've tried reflowing more joints just in case but that didn't do it. If it helps pinpoint things at all I've noticed that the back right EL34 has a tendency to physically ring. Even if the tubes are swapped around, the tube in that position starts to ring. I've tried putting in mullards, which didn't ring, so maybe the mesas are just more susceptible to ring as a result of whatever is going on.
  5. Watches

    The strapmaker is combat straps, based in Montreal. Also made shipping alligator leather a little simpler than if I ordered elsewhere. This pic shows a bit more of the dial texture, though it's still not quite how it looks in person. Gotta love the acrylic domes that these old watches tended to have too.
  6. Watches

    Really can't capture how nice the linen dial looks in photos. The 5740C is a pretty great movement, very accurate & the smoothness of the seconds hand is nice. Got the strap hand made since I wanted grey with round-scale alligator lining.
  7. The ultimate DIY? A Stax SRM-T2!

    Well I've reflowed a bunch of joints (probably more than was needed). Since then I haven't had problems with oscillation, excessive offset, etc. The sporadic noise seems to have gone as well, but of course just as I say that it'll come back to spite me. Anyway, thanks for the help. I think I can stop fucking with it and just use it to listen to music.
  8. The ultimate DIY? A Stax SRM-T2!

    Shouldn't have opened my mouth apparently, the T2 is acting up. I replaced the four K216s of the right channel with ones from my old board with resistors at their gates, also trying a 5pf bypass cap right now. Neither of these changes seems to have helped though. It's been a complete gamble when I first turn it on as to whether the offset will be fine, -30V or -450V. Sometimes I'd measure around -30V offset, then as I try to use a scope to see if there's oscillation, the offset fixes itself and there's no oscillation. Other times I'd adjust the batteries, which fixes the offset, then as I'd turn the amp off to put back the top cover it'd regain its problems when turned back on. Regardless of the offset/oscillation I get an intermittent scratchy noise. Just maddening.
  9. The ultimate DIY? A Stax SRM-T2!

    So I've installed a 10pf bypass cap. At first the value for offset was way high (like 400V give or take) but after adjusting the batteries it fell back to within normal values. The T2 has been on for at least 5 hours now, and it hasn't misbehaved in that time. I've had to go back and check after hearing some puffs of noise which turned out to be in the recording itself. At the risk of jinxing it, that seems to have worked.
  10. The ultimate DIY? A Stax SRM-T2!

    I was thinking of adding resistors to the gates of the K216s in the battery next. If I recall correctly this helped solve some noise in Inu's T2. I'll also try lowering the value of the bypass cap and seeing what that does.
  11. The ultimate DIY? A Stax SRM-T2!

    Well I loaded up the gerbers and took some screencaps of the relevant parts. There's certainly a difference between channels. I've also noticed that R86/R87 are physically higher off the board on the right, if that makes any difference.
  12. The ultimate DIY? A Stax SRM-T2!

    Put in the second 2.2pf cap just now, and the oscillation looks nigh identical as before. Guess I'll try changing the bypass cap value next. Edit: This is what the oscillation looks like with the bypass cap set to 20pf.
  13. The ultimate DIY? A Stax SRM-T2!

    Just the right channel, and it's come and gone up until now.
  14. The ultimate DIY? A Stax SRM-T2!

    Your board version is probably older than mine too, right (production v1.07/silkscreen v1.03)? Either way I'll see how it responds once I've added a second 2.2pf cap. On that note, what about soldering in SIP sockets to make swapping bypass caps easier?
  15. The ultimate DIY? A Stax SRM-T2!

    Seems like oscillation was indeed the cause of the noise & high offset which has been sporadically happening. Happens now with either tube or solid state input. For reference both channels have 15pf bypass caps across the 100k feedback resistors. What about populating both C12 & C13 with 2.2pf caps? Apparently doing this killed the oscillation in pedefede's T2 a few years ago.
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