O/L Problem with 6000's B bus + missing most 688 card schematics **SOLVED**

[SubspaceSound]

Hey all! Can't believe it took over a year to make my first post here. I made this account just before putting the money down on what is now my studio's 6056 E, and just now I've got time to join the community

So, this 6000 came to us in rough shape, and the service manual is beat up and missing a fair number of pages (not to mention more than half the DL snakes missing, no card or board extenders, crimp tool etc). The previous owner and tech did a few really janky things to it that we've since undone. Most of the console has been taken care of now, but one problem in particular has been sticking around: The B bus won't pass signal, it's O/L light is always on, and it seems to be trying to output DC to the master bus. But of course, the manual is missing every single schematic for the 688v with the exception of the 256 card (which is the original print... go figure).

I could get as far as isolating the fault to the 157b, before one of the quad op-amps, but without the schematics I'm stumped. I'd be eternally grateful if someone has those schems kicking around on their computer and could share them!

[Chris Simon]

Hi There,

Here's the 82157 schematic. Hope that helps. I have all the 688V schematics, but it's a 16 Meg file, and I can't post it.

Chris

[Frank Cross]

Strange read. I have the exact same scenario as I'm also restoring a 6056. I have all 56 channels fully working, entire console recapped. I have some minor issues in the 688 such as a channel passing audio set to A will play on A but if set to B or C will also play even with those not enabled on the 688.

I'm about to finish up the LED mod for all buttons and the VU's before getting into the 688. I also have a lot of spare 688 cards if you happen to need any. Once this console is finished I won't be getting another 6k so there isn't much need for them.

I can attempt to scan the chapter for the 688 and save them as the smallest file size possible. It might come in at a smaller size to post.

[SubspaceSound]

Strange read. I have the exact same scenario as I'm also restoring a 6056. I have all 56 channels fully working, entire console recapped. I have some minor issues in the 688 such as a channel passing audio set to A will play on A but if set to B or C will also play even with those not enabled on the 688.

I'm about to finish up the LED mod for all buttons and the VU's before getting into the 688. I also have a lot of spare 688 cards if you happen to need any. Once this console is finished I won't be getting another 6k so there isn't much need for them.

I can attempt to scan the chapter for the 688 and save them as the smallest file size possible. It might come in at a smaller size to post.

The 688's logic can be a nightmare... luckily, you don't see too many compounded failures on those cards. I consider myself lucky that other than the one troublesome 157, the rest of the 688 needs nothing more than some calibration and recapping.

I don't know how most people here handle redistribution of the schematics, but if the PDF for the 4000's service manual can clock in at 10 MB then just one chapter should be A-OK.  I'm also looking close at LED bulbs, some of the bulbs in mine are janky custom LED jobs, the rest are the originals.

[xmax]

A lot of issues that happen in the 688 section come from failing "hybrid"
Op-amps. Personally I would fully populate the 26 cards and mod S3E
 to make "A" a true 4K. Take all the best 688 parts and fix up B and C for
"back buss" duties. Are the documents posted in the schematic section?
If not I'm sure I have them. 

[walrus]

I uploaded some scans from my training course manual in a link in the Tech Docs section...
http://forum.sslmixed.com/index.php/topic,560.0.html

[SubspaceSound]

A lot of issues that happen in the 688 section come from failing "hybrid"
Op-amps. Personally I would fully populate the 26 cards and mod S3E
 to make "A" a true 4K. Take all the best 688 parts and fix up B and C for
"back buss" duties. Are the documents posted in the schematic section?
If not I'm sure I have them.

Right now, I don't have any problems with the sound of the 6K's hacked-up summing. With Rock stuff it even adds a bit of that edge that this console's transformerless inputs lack! If I was gonna mod the busses somewhere down the line, I'd probably go with a custom-built unit, something with different colors for each bus, i.e. super-clean, 2520, and OpAmp Labs summing

I uploaded some scans from my training course manual in a link in the Tech Docs section...
http://forum.sslmixed.com/index.php/topic,560.0.html

Thank you so much man! Somehow I missed your old thread every time I looked... just goes to show that just because I can hold a soldering iron the right way round, doesn't mean I can read.

Edit: As it turns out, the fault in the 157 was a lot more boring than most of y'all thought. Contained within this console's slightly seedy history was a complete failure of the original PSU's negative rail, which roasted a number of the 10ohm fuse resistors in the dynamics cards, and as it turns out, this one resistor in that single 157. After replacement and cal, the whole 688v is up and running once again!

[xmax]

Good news! And yes I have installed API and 990 summing amp on the b and c buses
already.