NEED HELP! URGENT! Erratic behavior of 651 centre section

[sintech]

Here's pics of the standard 24 card for reference for the mods to Marc's board.

[marcmozart]

OK now I found something...

I just checked the voltages on the inputs of the Logic Controller IC T1 (pin 55, 56, 57 on the back of the center PCB)

They all show about 8V (against 0V rail) with 2 buckets of channels on.

With all buckets on these values increase to 13V (against 0V rail).

Conclusions?

[sintech]

You maybe witnessing the loading from having dark buckets, I did some loading tests last year.. and the logic rail dropped as I populated dark unpowered buckets.

[marcmozart]

Update: I've just ordered a bunch of these CMOS ICs for the 024 Logic-Card.

Looking at the specs of these they can be run from 3 - 15 V so the voltages I've measured should all be fine.

I've compared my 024 card with sintech's 024 and recognized that T1 is a 4042 CMOS IC ("quad latch") whereas my 024 card has a Motorola MC14013BCP (a 4013-type "dual type D flip flop") installed. I could not find any evidence of these being compatible but will just order one of each and see what happens replacing them.

[sintech]

Hi, this would explain all the cut traces and mod work at a the back of your 24 card, it's all in the T1 area.  Stick to the 4013

[marcmozart]

Hi, this would explain all the cut traces and mod work at a the back of your 24 card, it's all in the T1 area.  Stick to the 4013

Who and why would do something so cruel to my 024 card 

Will report back once I replaced the MOS ICs...

[waltzingbear]

Probably SSL

Alan

[marcmozart]

Update: I just replaced all the CMOS ICs - unfortunately it didn't solve the problem.

Any other ideas? I really appreciate your input.

Thanks,
Marc

[xmax]

Recal one supply to about at center section with ALL channels pulled (fun I know) then
add channels one at a time until shit freaks out (recalibrate p.s. after each bucket) I did not have time
to read the whole post but it sounds like the center section works fine alone, or try pulling the ribbons
on one side of each center section, first right side then left side.
it sounds like you have a bad bucket or module freaking it out.
are you solos's working properley? good luck. N

[xmax]

I would highly recommend pull 3 modules on each side of the center section and pulling The top 3 ribbons, then calibrate the p.s. to exactly+/- 18 and of course 6.5 between 18 and 13, I have never seen a logic chip fail in the center section, and with over 20 years on this crap I have maybe seen 3-4 chips fail at all! (unless there is a ps problem that kills them) what I have seen fail on these desks are logic related diodes and fets. they usually short out, and one channel  or bucket or ribbon can often freak out the whole desk! on any of the mini monitor switches you should see a logic swing from -18 to +18. N

[marcmozart]

Pulled the top 3 ribbons on each side of the center section, however nothing changes.

I would highly recommend pull 3 modules on each side of the center section and pulling The top 3 ribbons, then calibrate the p.s. to exactly+/- 18 and of course 6.5 between 18 and 13, I have never seen a logic chip fail in the center section, and with over 20 years on this crap I have maybe seen 3-4 chips fail at all! (unless there is a ps problem that kills them) what I have seen fail on these desks are logic related diodes and fets. they usually short out, and one channel  or bucket or ribbon can often freak out the whole desk! on any of the mini monitor switches you should see a logic swing from -18 to +18. N

[marcmozart]

Here's a detailled report… (with a video clip)

- when I switch the desk on, the bulbs for MONO and QUAD switches on the MONITOR MATRIX are burning

- the channels are always stuck in Film-Mode, and the Monitor Matrix can not be switched from FILM to QUAD / STEREO. The MONO light is always on

- I can get a signal from EXTERNAL TO MONITOR, when I press the DIM button, the signal gets cut and the MONO button bulb goes out. Same when I press the CUT button.

- Whenever I switch on more than 3 buckets, all signals from both EXTERNAL and the QUAD BUSS get cut. I've already tried to remove the top 3 ribbons on the left and right side of the Master Section to rule out that it is not one particular Channels that makes the Logic Board go mad.

- The entire STATUS-section works fine.

I have uploaded a movie to this link:

https://app.box.com/s/v3g8ulhjmurp0vtd98h7

I think I remember that when the problem first occured, I smelled like burned electronic parts for a moment. Could be wrong though. What part could potentially be blown? As I mentioned, I replaced all the CMOS ICs on the 024 card already.

[sintech]

Crazy, as all these operations relate to the 24 card.

Could the bucket's going on be a bad diode? letting voltage travel the wrong way into the 24 card.

You could look for a diode gone short circuit on the 24 with your multimeter.

[marcmozart]

Thanks! How would I test for a diode gone short?

Crazy, as all these operations relate to the 24 card.

Could the bucket's going on be a bad diode? letting voltage travel the wrong way into the 24 card.

You could look for a diode gone short circuit on the 24 with your multimeter.

[sintech]

You can put it diode test/continuity (if it's short it will beep)