Tinkerer

Okay, so I'm getting into the bolt down stage (everything tested but the actual circlotron output) while I wait for final parts on my outer panels and I needed to double check some layout stuff. How much does it actually matter to have the transformers as far as possible from the PSU's? The easiest way to wire this would be to have the PSU's in the back, the transformers up the middle and the Circlotron output stage nearest to the front panel. This thing is spacious enough I'm hoping it's a nonissue compared to smaller amps. I was going to mount the potentiometer in the back and have a rod run through the length of the amp to the front panel. However, this means it will be running directly over the top of the three transformers. Though as you can see from the picture, it will be about 8 inches above them. How much of an issue will that be? Is it still better than having the potentiometer in the front and a really long ass run for the audio input from the jacks? Excuse the half finished case and the backwards potentiometer but should give a sense of the spaces involved. 12U, a real tub for sure.

Not audio exactly but my new modem has been overheating causing it to drop connection and restart all the time. I took it apart and the silicone pad for the heatsink wasn't installed right. Since I had it open, I grabbed a bigger one out of the old parts bin, tapped a couple new holes in the sink to fit the board mounts and notched the cover so the heatpipe could fit through and used proper paste for the mating surface. Works perfectly and runs way cooler now. I need that reliable internet to waste time here after all. Old sink on the right

Could you be more specific on why? The feedback was on a whole different board previously (output board), and would have had even longer connections that way. Edit: I just mean, is it that it can pick up noise or that the added capacitance of the wire mucks with something, I really don't know. I can add shielded wire if its the first but there's really not a solution to the second other than a shorter path, which would be pretty ugly point to point but easily doable.

Got some parts in from mouser and altered one of the amp boards. Guess there's really not a prettier way to do it unless you run all the wires underneath. Just double-checking one last time before startup. Pretty sure I did this right, but better safe than sorry. The +15 and -15 go to the rails right? And the hanging end of the 25K resistor goes to ground. Edit: turned it on, both LED's came on and nothing exploded. Gonna count that as a win. Checking the current and balance now. Edit 2: Okay. Current set to 10mA via .5V across the 50R. Default was around 15mA for both channels, that bracket got warm quick. I had to back the pots way off. Funny because the power supplies are almost dead cold all day long. Transformer was only lukewarm after all the testing.

I got one of those helipots. 20K resistance. It was a real pain in the ass to get one with all 4 gangs the same value though. Actually mine is 5 gangs but the first four are 20K. And I couldn't find a single modern "servo style mount" for it. Though I might just be searching wrong. I know I had a devil of a time finding good toroidal transformer mounting kits, but once I found a part number, it turned out Mouser carried them all along. EDIT: Wink, you know the resistance in the 4 gang one you listed? I never bought that one because it's not in the description and I wasn't able to backtrack the part code earlier this year. I just never wanted to gamble on it, if it was 1K or 200K or something.

I've already checked there and several other places. The problem is their biggest clamping mounts are 1.5" center bore or less, and I need a 3", over twice that size.

I have looked high and low for a servo clamp big enough to mount my big old helipot potentiometer and I've struck out. Anybody got a source for one with a 3" clamp? Otherwise, could I just use a rubber-lined munsen ring?

So mostly the driver board mods back on page 2? 200K from each SiC to the feedback terminal to keep feedback on the driver, and 2M from each SiC into the OpAmp for the servo? Then use the Output stage bias trimmer to short the servo input+ to ground? What about the other resistors and diodes in that post like the 100V diodes and the parallel reistors? Are they necessary or just part of converting the driver board into a standalone amp? Just trying to understand since I'm kind of a neanderthal when it comes to figuring this stuff out. I can monkey something together and follow instructions but actually knowing how everything operates is usually beyond me.

Right. What I'm asking is with the servo not getting input and not really doing anything, should it be bypassed completely? Or do the boards work fine if you just wire it up normally like this? Also, just double checking, but the Output low voltage input is supposed to be -15VDC like the silkscreen says right? I know the corrections posted higher up the the thread for the original output board are different than the current version we have, but I figured it's worth being sure.

Give the old movie a watch if you like 70's scifi. It's only about an hour and a half. The show departs drastically from it except for the main premise and a few thematic similarities though. The movie is mostly good for seeing what Terminator and Jurassic Park pulled from it later.

Bumping this back up to the top with a few more questions before I start hooking things up and hoping they don't explode. On the 4N25 opto relays. The ones I got didn't have the little notch to show direction. So I compared them to my Opamps and just used the direction of the printing on the top to determine which way to slot them in their sockets. Is that right? I have 6 6"x12" vertical heatsinks with 3" fins in my case to dissipate the heat from the boards which are mounted to 1/4" angle brackets. With 10 boards, not counting the onboard GRLV, I can stack two on every sink with one free space left on each side. My question is how best to mount the ten boards for best heat dissipation and the least interference. I thought maybe this way so I could get at both the output and driver boards from the top to adjust them while it was running. Related to the driver board. With the new output boards, what needs to be changed/left unpopulated/jumpered on the driver board for the driver to function correctly, if anything. What is the voltage I should be aiming for on the test points to have the correct current set on both the driver and output boards? Is 20awg thick enough for the 900V lines? I have some 4kV wire laying around in that size. Some of the AC runs will be a bit long on this amp because of the size of the case and transformer placement. Other than twisting the leads, should I also do anything like get some braided shields to sleeve them in and ground that to chassis, or is that overkill? Last, about what size fuse is needed for this amp? VA rating of all three transformers I have put together is 1000VA, so even though they're overbuilt that would still be what? 10A?

Made the regular adjustable voltage divider since I had all the parts. Turned out great. Thanks again.

Thanks for the recommendations guys. It's a good point about the brightness. I almost forgot how blinding they can be depending on the manufacturer and color. Looks like I have everything in my parts box already but an LM317 to make a variable one, and they're cheap. I always like a fifty cent solution.

I had another quick dumb question. Looking at a lot of the LED lit power switches, the LED's have a 12VDC rating. Since most of these are meant for things like car applications where they're running at 14-15VDC anyway, is there any reason not to just let it run a little overvolted off a 15V PSU straight?

Thanks, for the link. I guess I'll err on the side of caution for this build and get some proper ones from mouser. But I'll keep them around for less heavy stuff, like if I want to rebuild an old stax amp and replace its one turn pots.

I was going through some components for a project and realized that my trim pots were Chinese clones of Bourns (Baoter). They measure and tune fine though, look pretty decently made. Is there any major issue with using them?

There's an early 90's STAX DAC up there too. Any good? I never hear much positive about any dac that old.

Got the new Circlotron V2 output boards. Looks great! One question. The new pots on there are to directly adjust the current right? But the old ones had those connectors that I think went to the opto servo on the current source boards? So does something need to be jumpered or no longer populated on the amp boards? I don't have the schematic in front of me to see if that circuit is separate from everything else.

Excellent. Can't wait to pay shipping and get those version 2's.

Paid

As long as there's several group buys going on, any chance we can get one for the updated output boards (V2) on the Nanotube?

Bit of a silly question, but what is the best kind of lock washer to use with small nylon screws so they don't strip or snap? Split ring or inner toothed? And best to use a nylon nut or a stainless steel one? And secondly, in a really high voltage application where you have thick brackets (1/4"), is it better to use a nice ceramic isolator then extend the transistor legs with heavy gauge wire to reach the board properly or to use a thin silicone isolator so the leads don't need extending? I know neither is ideal, but looking for the lesser evil. I was leaning toward silicone but the center hole is 5mm on the ones I have and I was afraid the 1kv'ish voltage would be able to jump the less than 1mm gap between the metal even though the multimeter reads that it's isolated.

So, somebody tossed out an old Sony Trinitron WEGA KD-34XBR960 on my street, just about the last of the fancy CRT televisions from 2004. Took it in and gave it a once over. The tube was shot but the power supply and most everything else was A-Okay. So my question is, what is worth salvaging out of it? There's a bunch of onboard sinks that are the right pattern and pitch for what is used in many of the project boards here. Also a bunch of high voltage xicon resistors and some power resistors that look spiffy. Probably going to keep the flyback transformer in case I want to do a little plasma speaker build down the road for fun. Bunch of silvered mica and ceramic caps that look good in values I can use. But what about the devices? Anything special in the sand anyone might care for? Edit: Wrote down all the ones on the boards I kept, but its a few dozen different types. Rectifier bridge on the power supply seems to be a quartet of Vishay IRFIB7N50A's. Those worth keeping at all? They still seem to be in production so doesn't seem like anything special. At least its nice to get almost a dozen anodized TO-220 heatsinks for free.

Cool. Was hoping for a summary. Last correction I recall seeing here was just the back to back zeners. Also belated thanks on other help earlier. It was exactly what I needed, especially the CPF312R000FKB14 for the power resistors.