d8b fader issues

[TheJetTek]

My d8b has started having an issue where, upon booting, the faders are "stuck" at the bottom. Moving them from bottom to top and back a couple times "unlocks" them and they work normally. But if a fader receives any automation moves or if I drag the onscreen fader at all, the fader snaps back to the bottom and has to be "unlocked" again by moving bottom to top a couple times. At first it was just the first 8 channels doing this, now it's all of them. This happens whether in "normal" use or when using the ProBox. Same behaviour is both cases...

Any ideas or help would be appreciated.

[munkustrap]

For me there are only two possible issues:

1.) 12V supply issue --> Faders will gow down and stuck there. In this case you should also have Problems with your VPots. Are These working?.

2.) DACs on Faderboards are gone (dont ask me why). AD8803 (U908) 8 channel boards and AD8804 (U914).

I got 3 Faderboards for repair a few moths again with the same issue and on all 3 boards this component was broken. replaced it and it worked.

[TheJetTek]

The V-Pots are really sketchy sometimes. What usually happens is that I have to re boot the unit about 3-4 times before the probox firmware will load up properly and the v-pots stop going crazy. But then the faders are still having that same issue. If it is the 12V supply, how do I got about checking that? Is this something in the power supply on inside the console??

[munkustrap]

That sounds as a 12 v issue.
Maybe grounding between mgnd and dgnd is bad.
How are your skills on electronics?

You can check my manualnhow to build in a powersupply into console. There is a step soldering a gnd bridge
On the power connector board. This you can try to improve the gnd.
I can imagine that this solves your problems.

By the way. This issue generates multiple commands per seconds on the communication bus. Therefore the brain board
Gets stuck and cannot communicate. This is the reason why yyou need to boot several times.

Let me know if you have any questions.

Best regards

Munk

[TheJetTek]

If this is the case, is it likely that this has caused damage to any other console components?

[TheJetTek]

Ok, soldered the ground connection as shown in your power supply manual. No change in the issues. Any other ideas? One quite knowledgable person suggested the following:
"You may have a problem with the +/-16V from the CPU that is damaging the comparitor circuits on the fader cards."

Anyone with suggestions on how to test/fix such an issue??

[Crash]

You could measure the pins number 5 and 16 of the big ass connector and see if you have +/-16volts.

[Arslan]

If only one or two faders are not moving you could replace a single fader but if the whole board is not working you need to but a new one.