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Faders and Vpots DEAD. Please, please help?!

Discussion board for Mackie's d8b Digital Console users.

Faders and Vpots DEAD. Please, please help?!

Postby intolerance » Thu Jan 12, 2012 12:33 am

Hello all,

So I bought a d8b for a ridiculous price for use with Marc's d8bridge software. The faders and Vpots are dead, and I've tried EVERYTHING. All the LED's work along with the VFD display..all good. Communication with d8bridge all good. When you turn the Vpots, nothing happens and I've NEVER seen the faders move. I'm posting this here because I'm sure d8bridge is functioning as it should, so this is a hardware issue. I would be so grateful or any input on this!!!

Proplem: Vpots and faders are non responsive, almost as if their turned "off".

Trouble shooting I've done:

- Tested power all power supplies: Check. The Sparkle PSU is only kicking out 9+ volts instead of the required +12V's required to power the Linear power supply via the single molex connection. I have another PSU providing +12V to the linear psu via molex. No change.

- Tested all the pins on the Big Ass Connector: Check. Verified that each pin is receiving the required voltages. (as per the schematic)

- Verified the Brain Board is receiving required voltage: Check. Opened her up, cleaned and reseated all ribbon connectors (as per the famous ribbon cable issue) then checked both ends for continuity and required voltage is indeed feeding the brain board. Again, as per schematics. All checked out a-o-k.

- Verified the Fader Banks are receiving required voltage: Check. Verified that the Brain Board is feeding the correct voltages on each pin of the ribbon feeding the fader banks. I wanted to pull the fader banks out and test the faders motor circuit in correlation to the faders 'on/off' button, etc...but I couldn't find the right sized allen. I don't think this is the issue here as again, this is a global issue.

- Weird observation about the +16V: I was suspicious of the +16V, -16V, so on a hunch I provided my own +/-16V via a standalone psu I had kicking around, and the Vpots started working!? (Meaning; when I turn them they move the LED and send info to Cubase...as they should.) Faders still dead, but as you can imagine this was giant WTF moment as I've performed all the above tests with the standard default PSU's plugged in, and other than only getting around 9.4V where it needs +12V (easily fixed with other psu via molex, as stated previously) all +/-16V areas were cool. Hence, WTF???.

I'm totally stumped here, I feel completely defeated. :(

HELP?

What could be causing this? Everything's receiving power, d8bridge is working as it should, and everything else works. What gives??!! I feel like perhaps the faders were turned off at some point and need to be turned on somehow? (yes, tried the 'Faders Off' button) I don't know...Ideas? HELP?!

Thanks for reading!

-Aaron
intolerance
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Re: Faders and Vpots DEAD. Please, please help?!

Postby synthjoe » Sat Jan 14, 2012 2:32 am

9.4V looks a lot like a leaked filter cap in the PSU (PC style). A dried out main filter cap in a switch mode PSU (which 2 of the d8b's three are) will cause very nasty ripple on the power rail and it might result in peaks in the order of several 10 volts that might kill components. Maybe you have some problems with the +/-16V as well, it is needed to 'read out' the pot values (as referred to here). I suggest to do a full 'recapping' of all three PSU's and repeating voltage check after. Or a full testing of all three PSU's in 'real life' conditions (full range from 0 to max. load), but it might be more difficult to do without the proper test equipment.

If PSU's test OK (or after recapping) and voltage readouts are still off, you might have to dive in deeper...
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