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Tinkerer

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About Tinkerer

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  1. I got the 20awg PTFE stuff from naavships on ebay. It was the only multiKV silver plated stuff I could readily find. Unfortunately, only comes in one color so it's helpful to add some other markings to easily differentiate what goes where. Other stuff I just used the more standard silver plated teflon coated that's good to 600V or so. And I used two conductor silver plated shielded for the unamplified audio with the shield tied to ground. Been bringing an old IBM mainframe terminal and it's controllers back online lately so haven't got around to testing the new stuff yet. I did put in an order for replacement parts for my HV900 though. Hopefully, I'll get around to more testing later this month. Thanks for the troubleshooting stuff Soren, but there's so much energy in this thing, the 10M90S always gets toasted along with the 10V reference if anything else blows. The ones in the power supply that died were all brand new. I appreciate the slow power up info though. When I picked up my old Conrad variac last year, I wouldn't imagine I'd get so much use out of it on all sorts of projects, but it's become almost as indispensable as my multimeters.
  2. Just loaded it with proper resistance the same way you did way back at the beginning of the thread. Looked like one of the CMF60's (the 100R next to the 1N4007 diode) had lost a chunk of insulation on the underside only and I didn't see it. Either that or the new SMD STN9360's were garbage. It's the only PSU that needed new ones since I had enough salvaged of the others. Also possibly the socket for the voltage reference as that seemed to have melted and soldered itself to the chip. Hard to tell what was what gave out and what got damaged afterward, especially when one of the resistors burned and covered a good chunk of things with soot. All the other three ran fine. This one got up to regulated voltage, lasted about ten seconds, then popped. All the solder joints were good and the board itself was squeaky clean before it got powered up.
  3. Bumping this as I got some more multi KV rated silver plated wire in, enough to give all this a good test in a day or two. Had one of my reconstructed HV900 supplies blow under stress testing, bad resistor I missed I think, so will only be testing one channel. I'll let you guys know how it goes. It wouldn't be Fourth of July weekend without some fireworks after all. If anybody else has been working on this, now would be the time to pipe up if the latest current limiting mosfet additions worked for you or didn't.
  4. Soldering station recommendation

    I've been using a Radioshack one that I picked up on their going out of business sale for $30. It's similar to a Hakko 937 and uses the same tips but a little fancier in presets and stuff. I really like it a lot, especially the nice cheap variety of tips you can get from china for next to nothing. Best part is the quick heating and ability to keep a consistent temp on the tip even when soldering some larger stuff. It doesn't really bog down unless you're desoldering a big heatsink or something. Though I guess anything compared to my old plain twenty year old iron would be a pretty big improvement.
  5. What Are You Building Today

    Turning an old capacitive terminal keyboard from 1978 into a modern USB keyboard with fully programmable keys. Got it working fine, but had to tear it back down for keycap polishing and a few minor tweaks. Currently reapplying dielectric lube to all the key stems. Need to finish up this project so I get back to testing Circlotron stuff.
  6. Gonna test the current limiter on the HV 900's today. Just double checking that this is the right setup. If it works, I should have at least one channel up and running today. EDIT: I'm just trying to puzzle it out. Diode direction for an N channel mosfet should be Source -> Drain, right. Then the resistor is 60 ohms to get a voltage drop of -20VDC to activate the depletion mode gate at around forty something miliAmps to give some buffer room for the device to fully close before the 50mA limit on the output boards. I know this is simple stuff, but when it's a hundred bucks in exploded parts and worse, the time to pull everything apart, test it and fix it up again, I just want to be 100%. I had one other question though. The output stage bias trimmer on the driver board. We keep that shorted since the two pots on the Output V2 control the bias current directly now? And is the extra DC offset resistor still required if feedback is run from the output board like the silk says instead of from the driver board? EDIT 2: Nevermind, I get it now. I need to swap them around. The body diode is supposed to point back the opposite way to act as a suppressor.
  7. The ultimate DIY? A Stax SRM-T2!

    I saw you had to send the PSU front plate back about three times. Magnificent patience all around to make everything just right. I barely had the patience to beat together my circlotron case out of a server rack and some extra parts when they mailed it with chips and scratches.
  8. A 12000 euro amp

    That's a shit ton of tubes and transformers. Looks like a mainframe module from 1956.
  9. The ultimate DIY? A Stax SRM-T2!

    Gorgeous!
  10. goldenreference low voltage power supply

    The toroid came from some other big amp. I bought it second hand awhile back. The setup for the primaries is weird. The 220 is a fully separate winding.
  11. goldenreference low voltage power supply

    Got my spare parts GRLV PSU all finished up for the mini stax amps today. Wiring is a little ugly since I left the transformer leads long in case I ever want to repurpose the transformer again and left the other primary intact for 220V. Used an inline fuse because there wasn't really a good spot on the back panel that wouldn't look weird or collide with the board. The Kemet caps were nice and short enough for me to put in the case but since they're fat required adjusting some of the other bits before soldering to make sure they fit. Had some decent little heatsinks on the pass transistors originally, but even though the amp only pulls about 300-400mA, they got way too hot too quick. The bottom plate worked fantastic though and once assembled, the whole chassis spreads heat to all parts pretty well. And I just noticed in the picture that I forgot to scrub all the flux off those when I remounted them. Well, better go fix that. Hope you guys enjoy this particular combination of spare parts pile and overkill. Only cost me about $70 to put together with what I had laying around and half that was the case.
  12. goldenreference low voltage power supply

    Just a heads up that 7v reference and 1.07kOhm RN60 worked fined for 12V output. I powered it up and +11.98 and -12.00 dead steady on the board. Only need the +12 half for my purposes but I figured if I ever repurpose it later, it's easier to swap around a couple resistors than hunt down some transistors that might be OOP years from now.
  13. The Headcase Stax thread

    Does anybody know if the new US STAX distributor is up yet? I need a couple parts to refurbish an old Nova, and they're the cheapest for what I need.
  14. goldenreference low voltage power supply

    The nice thing about that case type if you look at the back is that it already has a few milimeters of isolation around the hole, unlike a TO-220. So the screw is all you need.
  15. goldenreference low voltage power supply

    I just used the same ones I use for all my TO-247 stuff. http://www.mouser.com/Search/ProductDetail.aspx?R=4180G
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