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D13 is right beside the 2SC1815 (Q20). I'll try swapping a few 4686's with spares, and D10 too since that looks suspicious to me (since it's right beside the +15 input). Edit: Well it's not any blown LEDs, they all light up after applying voltage directly to them. Still puzzled as to what would cause only D13 to light up. Also, measuring the -HV input on the problem board I get about -63V (-459V on the working board).

Well, there are no burn marks or anything visual that would indicate a bad part. I'll try and see if any of the 4686/1968's are blown (sure hope not though). Edit: It doesn't seem like the output transistors are the problem, their hfe all check out according to the spec sheet and unless I'm reading my multimeter wrong they seem to pass the diode test. Only D13 lighting up seems a little weird to me though, shouldn't D10 be lit as well?

I shut it off right away when I didn't see every LED light up, but remeasuring I got +457V on both +/- outputs of the problem board (while I get -a few volts on the good board since I set the balance/offset while it was warmed up).

So after testing the boards I got one to balance & offset fine. However there's a problem with the other board. Only one LED lights up (D13). I checked beforehand for possible shorts and didn't see anything, also made sure to hook the signal inputs to ground. Any obvious spots I should check first?

I let it stay on for another hour or so and those measurements didn't budge.

So after powering on the PSU board the first time (450V version) I get +459, -459, +15, -15, and +569 for the bias before the 4.7m resistor. Is 9V over on the HV rails anything to worry about?

They shipped it out on thursday and I got it tuesday morning, so pretty quick. Then again it arrived in canada on friday, so most of the shipping time was spent between customs and me.

Got the dissipante in from modushop, now I can start the hard part of the build.

I'm in for some 4686 & 1968, would certainly be a lot cheaper than off bdent.

Made some progress on the psu board. Though I forgot to get enough 150V zeners and .22uF caps with the right lead spacing. Anyone have extra PEEK screws they wouldn't mind selling me? 100 screws from solidspot is far more than I'd use.

Just to confirm, this is a 24V zener right?

The new site design really is a mess at the moment (the customer service tab just goes to 'page not found'). Anyway I sent them an email about the 4686's. I'm not holding my breath though, as it doesn't show on their product listing either.

Is there another reliable source for 2SC4686A's? Or perhaps someone willing to sell at least 12? Bdent's stock apparently ran out (doesn't even show up on their searches anymore).

Interested in those 1486's as well (would beat paying $35 for ten pieces on bdent). Also, is there another source for 2SC4686A's? Bdent's stock is apparently out. They were in stock when I checked about a week ago (really should have bought some then).

Hmm, even the 4170G is backordered too. I've checked mouser, digikey and future electronics for both of them so far.

Is there anywhere with 4171G ceramic pads in stock? All the sites I've checked have them backordered. Or does anyone happen to have a stockpile of them and wouldn't mind selling some?

Makes sense. My original confusion came from seeing other peoples amp boards with those jumper spots empty. For example this one (I grabbed this from this thread but I forgot whose board it is, sorry):

Here's the bit I mean: As far as I can tell it's just another bit to connect the traces on the bottom.

Hmm, I don't see that servo section on my amp boards. I assume it's because of the limited space on the offboard amp boards though. Which of the jumper spots are necessary to fill in if I intend on using the 1968 CCS? Also I need a wire from that single point above the 5pF cap to the 20k resistor right? The 175k resistors below the t-block are a bit in the way, but it shouldn't be too much of a problem. Anyway, I've done all I can at the moment until I get more parts or the replacement PSU boards in.

Are those 5pF caps on the amp boards necessary? I'll order some of those when I get the rest of the parts I need if so. Nevermind, found some among the pile of parts I have.

Yea there are six 100k resistors on this board total. I'll probably just make another smaller order with mouser after some more resistor stuffing (since I foolishly forgot to order two of each of the balance/offset pots). So, could I put a 3pin switch over the global/local jumper pads? Also, I assume mixing local on one set and global on another would be bad news right?

Is there an updated schematic for this amp revision floating around? I assume I use a jumper between which feedback I want and the middle pin (and solder the 100k into the appropriate spot). How much does the difference between the two matter?

Yea, I'm probably just being overly cautious. I'd rather that than not cautious enough and have things blow up in my face, though.

Before I make an order with mouser, would anyone mind checking over part substitutions I've made? Some of the parts listed in ujamerstand's BOM are unavailable (or backordered) and I've tried to find a part with identical specs to replace it. Except for the bridge rectifier they're all caps. The original mouser part # is to the left and the substitution to the right: 512-KBU4M > 625-KBU6M-E4 80-C322C102KDG > 80-C330C102JDG 80-C330C474M5R5CA > 80-C330C474M5R-TR 75-561R10TCCV47 > 75-561R10TCCV47BA 661-EKMH250VNN472MP > 661-ESMH350VNN472MP3 If the higher 35V rating doesn't really matter I'll grab the original cap here

Only one file, here's what the layers look like: http://i.imgur.com/aBPX9sU.png