Tinkerer

Speaking of the elastic giving out in the old Mk I headbands, I have to shorten the elastic in mine about once every two months to get it back to spec. But then I use them practically every day and they rest on a stand when they're not being used with a dust cover on top of that weighing them down. Is that pretty similar to the rest of you guys? One of the reasons I haven't bought a new headband is that I'll be ticked if I have to do the same adjustment no matter what.

So I had a question about some Dale stuff I got from Mouser. Bought a few months ago but only really started going through it now after I got all my heatsinks and transformer stuff together. Online when I bought it, and on the label it says 1/2W-1W. But looking at the size of them and the data sheet it says rated for 1/4 watt. They're CMF60 series. Had a few of my xicons that showed up too small as well. None of the bags are opened. I don't know what I can do or exchange at this point, but I want to make sure I'm not stuffing boards with parts that aren't going to cut it, even if that means rebuying/returning some things. I'll go reference the Carbon BOM for anything that crosses over that can help, but I thought I would post here in case there were any obvious pitfalls I'm missing. Also a dumb question but what is the brand/label series for the bright red power resistors with the marked bands? I took a shot in the dark and wound up with some of those chalky looking BC ones. But with the circuit needing them increased to 12ohm, I needed to buy new ones anyway so I wanted to make sure I got it right this time. EDIT: Probably a mislabel on the mouser end. I accidentally even got a couple itty bitty CMF55's stated to be 1/2W. Guess that's a lesson to me to read more carefully instead of just searching by voltage, type and power rating when shopping for resistors.

I had an ESP-6 that I totally refurbished at one point. Cleaned up the boards, resoldered everything, replaced nasty traces with solid copper point to point, all that. The transformers, all the resistors and ceramic caps were still good. The standard Koss pads for it are the 4A, not 4AA IIRC. But I found the best replacement is the Brainwavz extra thick pleather memory foam. Comfy and the seal helps out the somewhat anemic bass. The headband can also be replaced with a much more comfortable Realtek Koss clone from the same era. I forget the exact model but there are a couple. Also converted it to a removable cable since the old one was shot when I got it. Amazingly, the peak lights still worked though. They were the first stats I ever owned, and I kinda miss them. They were a bit weak in the bass and had a couple major treble peaks but pretty good for such an ancient brick. Their major weakness was not being able to crank them up loud I think, and how they didn't take EQ that well. I still have the speaker tap adapter box that came with it converted to balanced for my old orthos though. Fixed up stock And with the mods and different parts swapped in

Got around to making a quick and dirty model using the 5U case internal dimensions and the measured dimensions of the boards, my toroidy transformers, and brackets and such. Looks like there's room but you have to make best use of the vertical space. I don't really know what affects what like the real gurus here but I just tried to keep all the PSU's together and give the stacked amp boards their own space in the corner, as well as left space along the bottom back of the case for power plug/fuse/inputs/outputs. There's an inch or so left near the front that you might be able to shift everything even further away from the transformers as long as you keep all the faceplate controls in the center. As is, there's space to have the jacks or front power button offset. And model is here for anyone to play around with. http://www.mediafire.com/download/t7jk13n7s2ky166/Amp+mock+up+6.obj

I have a general potentiometer question. Anybody ever use one of the giant old milspec helipot potentiometers for volume control? I found a 20k quad for fifty bucks that I figured was worth a shot. The tolerances are good on paper but it's massive, like bigger than an RK50 quad massive. EDIT: I got this in today for anyone who needs a laugh at the size of it. Turns out it was 5 gang but I only needed the 4 20k and not the single 30k. So good and bad. Good: Pulled out my multimeter and gave it a once over. 5% tolerance on each gang is actually within 2% at max resistance and each gang is within 2% of each other at almost every point. Still tracks exceedingly well. Bad: sin/cos 360 pot so you only get a fraction of the manual adjustment for volume and would have to mark the volume indicators carefully. Old pot so old pot problems are likely. Still really impressed all things considered. For fifty bucks it was worth a gamble. I'll try hooking it up to my kgsshv at some point and get a listen.

Got mine yesterday. Thanks for managing all this.

The dual primary order should still be structured the same. 117 100 G 117 100 G CG, left or right or shuffle the center tap where-ever. So the 117 plug position should have both the 117's tied together and the grounds tied together The 240 should have them in series. The 100 should have the two one hundreds in parallel And the 220 should have a 100 and 117 in series So easiest way would be to record what pins are connected on the switch in each position, then sudoku it out. Which is just a roundabout way of saying what spritzer said really. At least your new trafo should have all the wires labeled so you don't have to ohm that out too. Just looking at it, I think the top row is all the primaries in proper order. Gray and white are the two 117's and yellow is the CG. But I'd certainly check it.

You used the 400mm one for that stuff, not the 300mm right? EDIT: Doesn't matter. Got my overspecced transformers in today from toroidy and they are way too big to make it work I think. Will take some measurments and double check later.

Sort of related to G600's question. Has anyone confirmed you can fit everything in a 5U case? I'll need to order my case sometime soon, and while my local machine shop will give me a pretty good deal on a custom if I have to get one, a modular 5U would still be quite a bit cheaper.

Just saw this post. Glad you're enjoying it. The 10S/12S really are great little amps.

Paid. Looking forward to them.

So what would be a good va rating for the two 380VAC transformers to give a little headroom?

So this wound up being kind of funny. I checked everything, and I mean every part of that side. Used multimeter resistance mode on the transistors to double check them and compared values to the good side. Everything matched up. All the top trace stuff to ground went to ground. All terminals were fine with or without wires screwed in. The couple little bridge traces were fine. So left with nothing else, I went trace short hunting systematically, every point to every other point. Then I finally found the culprit. The last time I had replaced the 10m90s for that rail, the solder pad for one leg lifted up just a hair and I had pushed it back down and soldered everything up fine. But moving the board around must have snapped it somehow, or maybe it happened when I double checked the tightness of the screws on the heatsinks. What it left me with was a shorted trace that you couldn't see at all under even magnification. Ridiculous. Took less than half a minute to remove the busted loose pad, score a bit of the trace down to copper, tin it, bend the cut lead over it and solder it properly. Then everything fired up, just as it should.

So I was fiddling with some things on mine today, putting in a new potentiometer, shortening a few cables, sleeving some of the wire runs with fiberglass to clean up the guts and as practice for cable management on the circlotron build. But when I tested the power supply before hooking everything back up, I got gremlins in that same damn +500V side again. No pops or sparks but it's outputting 182 VDC/402VAC at the +500 terminal. The trace tapped from the positive end of the HV rectifier bridge is 482VDC. These are new parts, but it should be the rectifier bridge since there shouldn't be any AC beyond that anyway right? Because the big caps behind that are for smoothing and the rest should be regulation? I know the resistors are all good. I desoldered and checked them all on the +500 side last time I had a problem. Same with the axial diodes except just checked that they were still functional, and same with the caps, all take a charge. Terminal blocks all connect to traces and nothing in them connects to ground that isn't supposed to. Anything else I might be missing? I guess the lesson here is never continue to touch something when it was already working fine. I'm this close to just getting a new PSU board and transplanting the known good parts since all the soldering and desoldering especially on the sand locations is starting to make them a little rough, and that goes double for the solder pads that connect to traces on the top of the board.

Welp, soren called it. Cold joint on the terminal block. Must have missed it when I reflowed the components originally. That was a lot of desoldering and hassle over nothing. Thanks for helping me work through things again guys.

Yeah. Both the 450VAC windings are fine. Same result if you switch them. Negative rail on the PSU ramps up to spec and the positive sits within a volt or two of zero.

First thing I figured when it went out was HV rectifier bridge, so I replaced that and the zener string at the same time just because I had the parts laying around. Didn't fix it. So then I replaced all the other transistors and diodes at the same time. Must've blown the new parts piecemeal then when I powered it up. Going to have to do the whole thing at the same time then now I suppose just to be sure. Well, I had to make a new mouser order for some other stuff anyway. Thanks. I'll give it another try in a few days.

Well, after everything running fine for a couple weeks, something gave out in the power supply. No pop or spark or smoke but the +500V just dropped down to nothing. Amp boards themselves are fine. On the PSU, the 15V+/- and the -500V are fine. The transformer is good. All the sand and the diodes were replaced on the +500. The traces look fine. No scorch marks under any caps or resistors I can see. I think it's become connected to the ground plane somehow past the R2 and R3 power resistors on the main +500 rail. I made a crude measured voltage map of the working and nonworking sides to compare. Working one might be helpful in the future for anyone else troubleshooting a 500V PSU on a KGSSHV. I know that sort of thing was asked about earlier in the thread. Mostly posting see if I'm on the right track or missing something really obvious. Sorry about the orientation. It was just easier for me to compare left to right.

Wow. That chassis is a work of art.

Just taking a crack at how many "get around to it" projects tend to sit in a box for years. Limbo probably would have been a better word choice. Thanks. I'm looking forward to just kicking back and listening to it for awhile. It certainly sounds great.

Yeah, if only for the overall cost and most of the casework, though I still had to drill a number of things like the feet, RCA plugs, switches, half the case screws were missing, that sort of thing. Board-wise, I'd prefer doing that from scratch. A lot less headaches. But there's a certain satisfaction in saving something from unfinished purgatory too.

Well, at least it's all worth it in the end. After all the questions and parts and time, she lives! And sounds great. The servos keep the IXYS parts within one volt balance and offset even at cold start. Only thing that didn't turn out so good is the attenuator I used that came with it. Unbalanced as hell and even has one volume click where one channel cuts out completely. Gotta get something better. At least max volume is just a jumpered connection so I can just use my preamp to control volume until then. The pictures aren't so great since it's storming like hell outside so natural lighting is pretty bad, but she turned out swell

The measurements referred to in the first two posts were taken at both the board's bias test point on the other side of C21 and at R42 each time where they were concurrent with each other. I just went and measured where R39 connected directly to the zeners later after all that because it was the most direct. It did make me realize something. If I measure on either side of R42, I get about a 50V drop on my multimeter. R40 is also a 100k resistor. So 580 -50 from the R40 is why I was getting 530V and why it measures fine at R39. It turns out I was just being stupid this whole time. So it seems everything is well and my issues with the bias were just cheap multimeter problems. Sorry to bother you guys about all that. EDIT: And wink called it

Doh, meant R42.

Yeah, it was really strange. But I was poking around the board and noticed something. I get 584V correctly where R39 connects to the string. It's just the test point and on the front connection of R40 where I'm getting 530V.