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Tinkerer

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Everything posted by Tinkerer

  1. So, having a couple problems myself, of my own making. Built one for 15VDC. Positive rail is fine at 14.98VDC. The issue is the negative rail. I'm powering it up with a variac connected to a spare transformer and it will kick over and light up all the LED's at around 18VAC. The issue is raising it to line voltage, the negative starts at -6VDC and just keeps going up as AC input increases. I backed it off once it hit about -23VDC. I swapped the Opamps and the Voltage Reference chips and same result so those aren't the issue. The MJF1531G was getting warm. I'm guessing the problem is with it or the Jfets? All the right parts are in the right places, but I bet something got toasted when I originally accidentally started it up with an MJF1531 in the MJF1530 slot.
  2. When I originally fired it up, the voltages seemed to automatically compensate for any adjustment I made. I would guess I because both halves are connected since I'm using a center tap setup. With all the stuff minus the boards and brackets installed, this was getting a little too heavy to move around by myself. It's easily a hundred and twenty pounds but it's the bulk that's killer. So I went ahead and put it where It's going to stay, next to my desk and shuffled everything else around. I just thought it was worth showing the T1W next to it for a size comparison. Final assembly continues, but it's mostly just cosmetic stuff like lengthening the transformer leads and sleeving them to make them look pretty while I wait on the last couple parts. This monster is definitely going to need a friend to help me move it if it ever budges from this spot.
  3. Alright, getting ready to get all the stuff together. Casework minus labels is done. Secondary power circuit is together and works, powering the solid state relay and the case LED's. Left it on all day. Voltage divider circuit doesn't get too hot and controls LED brightness fine. Inputs up to the pot are all wired. Keyed bypass switch works in all three positions (normal, potentiometer bypass, and loop out only). Audio wire shields all connected to chassis ground. Audio grounds themselves kept to their separate channels. Tried to test my GRLV+ as my last PSU board but I was a dumbass and didn't put the NPN/PNP MJF TO-220 pair in. Didn't realize I used two MJF15031's until I started it up and got horribly lopsided voltages. So a couple days until that part comes in. Also, what's the pots for on the GRLV+ again? Looks like they balance between the two halves of each circuit, but I'm not sure where to attach the multimeter leads to measure it. On the side of the 1M resistors closest to the pot? If anyone else is anywhere near completion on theirs and has run into any problems not mentioned in the thread. Now's the time to say something. Otherwise, I just had a couple stupid questions. You can run this single ended since it's basically a carbon with a circlotron output stage bolted on the front, right? EDIT:found the answer to CT transformer grounding. But now I'm wondering if having my grounding terminal block with two bolts to the chassis was such a good idea. Might have to isolate one of those screws. I think if nothing explodes in the next few days, it should be playing music by this time next week.
  4. Speaking of prices, I need to replace the sear spring on my old Iver Johnson Supershot top break. I've always done all my own gunsmithing but this is a pain in the ass where you have to knock out a number of pins and there's no exploded diagram easily available. I already got the part and a spare since they're only $2. The question is about how much would the price be for a real gunsmith to get it done? I know it's a cheap plinker but it has sentimental value. I'll drop a couple hundred bucks if that's what it takes.
  5. Yeah, just an old helipot precision potentiometer. It tracks extremely well and I don't fool with volume too much so I figured I'd give it a try. I don't mind giving up log volume control for the price difference between it and an RK50. We'll see if it was a dumb gamble or not once I get it all together. I got the parts to replace it with a more standard 4 gang audio pot if I need to.
  6. Getting some of the last back panel stuff done by hand before I give it a new coat of pain and labels. This is the relative position of everything near the back panel. I just needed to know if it's a problem to have a solid state relay and that little power supply that close to the volume pot.
  7. Most of the semis were the same price for me. Some stuff like the small fets were cheaper but out of stock. Similar situation on a number of CF60's in the right values. I remember I got a better deal on the main power caps, the tantalums, LED's, opamps, sockets and the voltage refs were cheaper than digikey,
  8. This would have been real handy when I was making my order yesterday instead of me digging everything up by hand. Also, somebody mentioned Arrow the other day, and I got about half my parts for cheaper from them including the voltage ref. The free ground shipping helped a lot too in making a split order between them and mouser.
  9. I can't believe how compact that all is. Makes my circlotron case seem even more ridiculous than it already is. I would hazard it's plain old heat shrink used to force the flat parts together to help keep the temperature drift between the two more in line.
  10. It's because the natural sources are so limited. Imagine if the federal government hadn't nationalized the reservoir in Texas all those years ago. Of course that might bite everyone in the ass now that the public production part of that agreement is coming to an end.
  11. I rewired my 007 MK I. Like most things, you just have to not be scared of it and have steady hands. It was more of a pain in the butt to find a place that had a spare cable in stock and figure out how to disassemble them without instructions than the actual recabling. It's just 3 small gauge wires soldered to 3 small soldering pads on each driver. The only trick is to do it quick, because if you sit there and pump a lot of heat into a thin polymer diaphragm, that can end badly. In other news, I had one of those days where I got both a good surprise and a disappointment at the same time. Got my T1W in and opened it up. Somebody went through the trouble to replace all the main power caps and the tubes the last few years. You could tell both by how good they looked and how the main board was squeaky clean while the pot and input boards had the appropriate 20+ years of dust on them. So once I changed the voltage to 117 local, I fired it up and it works perfectly. Balance and offset could be better, but within acceptable specs. I don't know how much of that is the tubes wearing or if they adjusted it at all. The pots seem to be in the default position. Will get it tweaked right in short order. So much for it being listed as "junk". Not sure if I even want to build the solid state tube replacements at this point. Probably should just to see how different it sounds since I have almost all the parts anyway. Just waiting on those sinks.
  12. One thing about the hammond sets, they're really nice but the main screw is not always the right size for certain transformers. Sometimes the washer too. Like with toroidy transformers matched by VA, the rubber pads are the right size, but the screw is too big for the M6 hole, and for some the washer needs a little ear cut off to account for the transformer leads .
  13. Pretty sure it's just "golden" anodized aluminum or maybe copper washed? My sinks I'm using for my carbon circlotron build have the same finish, but it's just regular old aluminum underneath.
  14. I had another general question for anyone who has used rod extensions for their potentiometers or attenuators. How essential are panel bearings? Do you use them at all or just have pretty tight tolerances in the hole of the front panel?
  15. So just two of those per tube straight triode replacement and enough sink to dissipate 5 watts a device? No diode and resistor between gate and source for feedback or anything? Just asking because I don't have a clue about the design end of things.
  16. This was what I was thinking. With the pot left hanging in the bypass position, shouldn't make any difference right?
  17. Basically, but it's a neat gimmick to remove the pot from the audio path if using a preamp and I already have the part.
  18. So I got an SRM-T1W for a deal I couldn't refuse. I thought it would be fun side project to fix up since I've never heard a T1 before. I've never really dealt with STAX tube amps before so I had two questions. First is that this likely still has the original tubes, so is there any easy way without a tube tester to tell if they need replacing? Secondly, I was hoping for a solid state equivalent circuit for the 6CG7 that I could build to try out. Otherwise, just going to be doing the usual cleaning, adjusting, replacing electrolytic caps etc.
  19. I have a Chicago Grayhill key-operated 4 gang switch I was thinking about using as a volume pot bypass. That way I could have my amp direct drive or not like the switch inside some of the STAX amps like the 727. Is this a terrible idea? I know it's dead in the signal path, but I don't know how much it would affect the sound if at all. It's a quality rotary switch, made to last a hundred thousand operations. I was originally going to use it as a main power switch but the rating is too low.
  20. I know the R8 and R9 have to be changed even if I was using the silk AC input value. I assume with less, the R10 and R7 as well. I just don't know to what. Will try to figure it out when the group buy boards come in. I know a few people upgraded their Carbons with the GRLV. Since that's the changes I need to do, if that's specifically documented anywhere, I'd really appreciate anybody letting me know.
  21. No, was just looking at the board silk for 20V and the comments of the thread. If it works, that's great. I would assume I need to change some of the resistors though?
  22. So, looking more closely at the GRLV board and reading its thread, I realized the 16-0-16 carbon secondaries aren't going to cut it with a 4 volt drop when I want 15VDC. This means a 4th transformer. I actually found a nice used toroid for only $30 shipped with the mounting hardware and the right rating. It's trying to cram that in there might take a little work. Somebody please correct me if I'm being stupid. Also, to get around the current limitations of the switches I'm using, I thought it might be good to hook up a 25A-rated relay with a heatsink. I'd have a keyed master power switch in the back for a small ungrounded 12VDC supply I made from a wall wart, and the circuit for that completed by engaging the front panel switch. I'd also run the LED's off this circuit and have the voltage divider to control brightness in front of them since it only take's about 3 VDC to engage the relay. Is there anything wrong with this setup for power? Oh, got the front headphone socket mounts drilled and tapped as well. And one last question, since I'll be drilling some back panel stuff next and I need to know this for jack options. Can this run single ended or only balanced? I know most of the other KGSS based designs can run single ended but I don't know how the output stage affects things. True push-pull is balanced only if I recall right.
  23. While I'm waiting on someone with some knowhow to chime in about the internal layout questions I asked, progress continues on the case. First side panel is mocked up minus the LED indicator for the hole.
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