by Y-my-R » Sun Sep 29, 2019 11:29 pm
Well... the power supply part of the CPU/rack-unit needs to work, for use with the ProBox. The computer portion doesn't really have to work for that.
At some point, I even had one of my D8Bs running with no mainboard in the CPU/Rack and only the power supply left intact, and it worked fine with the ProBox. It just needs proper power.
I didn't test any of the audio pass-through features that the ProBox allows in that configuration though (i.e. using parts of the master section as a monitor controller). But for use purely as a control surface, only the power supply in the CPU is needed. (I eventually got another CPU unit, to be able use this D8B as a mixer as well).
...and as @arjepsen said, for ProBox-only operation, you don't need any cards. No clock card, no fx cards, no i/o cards, etc.
You'd still be impacted by sticky fader problems, etc. though. Not sure how you could test for that, though, if you don't already have a ProBox to test it with, and do the fader calibration, etc.
Someone on here had a problem with the display in the top right not lighting up... so, that's another thing to check for.
You'll probably have to clean the v-pots. They were all very jumpy on the two D8Bs I have (and also on my spare that I bought for parts), and I'd think they most likely will be on such an old desk, if they haven't been cleaned before. So, that's acceptable, IMO, but you have to plan on spending a bit of time, cleaning the unit.
Speaking about cleaning... if the unit you're looking at misbehaves in some strange way, it's often also just about opening the bottom lid, and cleaning/reseating all the ribbon connectors you can get to (...and in some cases, also some that you can't easily get to...).
Don't try to clean the insides of the faders, though, you'd probably cause yourself more problems than it would do good.
But other than looking for physical damages, and to check if the mixer unit gets power, and at least boots to the dreaded "Error 43" screen, I'm not sure what you could check for, before you have a ProBox to connect to it (and your computer), and start checking if the faders and all other usable buttons etc. in ProBox mode behave properly.