Tinkerer

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About Tinkerer

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  1. Bumping this because I got my HV900 supplies all back up and running and need to make my last parts order to do some testing soon. I need to know the general voltage and current rating for the 60ish ohm resistor on the new current limiting adapter. Now that I looked at it closer, I think I get it. I didn't see the normally open part of the mosfet before. Also, if this works, I would assume the big resistors are not needed on the output boards. Though since I already have them, I'll probably install them anyway as long as I can find the sink space.
  2. Won't that need to be a 1kv'ish rated resistor though? Or were you guys thinking more of putting a couple smaller ones in series?
  3. Just a couple small questions. What type of case is best for the device for how much heat it's going to be shedding? TO-220 or TO-247? What value for the trimmer pot? Can we get a quick diagram of the circuit modifications with all alterations on the HV900? I just want to make sure I'm doing this right the first time. 50mA should be .6V across the 12ohm resistor. And about what's the minimum AC voltage on a variac you can set the current for this and the output boards before powering them up all the way?
  4. Yeah, didn't finish pulling, testing and cleaning everything until now. New 12V diodes are 5W and along with the new current resistors should beef that output board stuff up considerably. Plus being able to turn that on second after giving the driver boards a bit to power up should help too. I got them from Arrow. With the shipping difference it's about the same for small quantities. But thanks for the tip on the direct line. Might need that for a 7V ref for a different project. Those things can be a pain to find in stock at places for cheaper prices.
  5. Just a heads up that Mouser just got some of these in a couple days ago. http://www.mouser.com/search/ProductDetail.aspx?r=588-AP10162RJ Bit cheaper than DigiKey at the moment. FInally got all my stuff sorted and a big parts order to get the PSU's and output boards up and running. As far as I could tell, the things that blew were consistently. 12V diodes on the output boards all the time (some fused open is why I didn't realize this earlier) The diode side of the 4N25 half the time Big Cree devices on the output boards. Survived on the PSU's. Both 120 ohm current resistors on the Output boards always blew, the right less obviously as the damage was usually underneath. On 900V PSU's, 10M90S behind the DN254 every time. Other 10M90S and DN254 survived every time. SMD stuff, STN0214 always died, STN9360 survived rarely Voltage references always died without exception. Not fun on the wallet. BC557's died every time without exception Might save someone a bit of time if something goes wrong. Like you don't have to go hunting in the rectifier bridges or anything.
  6. So, I was just fooling with an SRM-Xh I got in. Everything turns on fine, all LED's on the boards light up etc. The balance on the right channel is within a couple volts. Offset is fine on both channels. But the left channel balance is almost -20VDC. There's no pots or anything on the inside to adjust. What's the likely deal? Carbon film resistors aging or did these things ship this way?
  7. So to reiterate on this. I should just need a lower voltage reference (7V) and 300? ohm resistors in place of the top 1.5K in each pair for 12VDC operation? Just want to make sure I have the resistor value right since I gotta make a part order soon for some other stuff and I'd like to get it all together. Also, is there any particular reason the STAX people put the positive on the barrel sleeve of the plug for the small amps? If not, it seems smarter to just swap the socket wires around so it can use any old common 12VDC wall wart.
  8. The problem with the single bridge on my boards (blue ones from the last GB) was the holes were smaller than the side ones so you had to drill it out to fit. I left the bridge lifted up a bit from the board so I could solder that top board trace from the top side to be sure it was connected right.
  9. Probably the trace on the top of the board for the bridge, that last leg closest to the AC input.
  10. Thought I would build my spare GRLV board and transformer into a 12VDC PSU for the little STAX amp. What value do I need for the R8/R9?
  11. Well yeah, you gotta desolder things to check them properly.
  12. Good one on a little transistor tester on my desk reads 4.4mA current and 3.1 gate voltage. Other good ones are within a little bit of that 4.6mA, 3.2V etc.
  13. Nice. I don't see any holes in the back plate for transformer mounts. Were you able to fit everything inside without resorting to that?
  14. I've been working on checking the blown parts in the HV900's slowly. Some parts good I didn't expect and some bad I didn't, like all the voltage reference chips. Did a bunch of alterations on the amp itself for quick connect transformer leads for testing and two stage startup as well from Soren's recommendations. But my question was about the new power resistors for the output boards. They don't fit on the existing bracket and will need a good few inches of wire to reach the pretapped M3 holes on the main sink. That adds up to about .25 microhenry of inductance for each pair. How much does that matter?