I'm back! Like I mentioned, I'm slow. It's sitting out where the Christmas tree should be, by the fireplace.
There's a 3' 10 pin ribbon coming out of the master section that doesn't have a place to land and I'm guessing it was for the digital i/o that never happened. Is that right?
If you're referring to the ribbon I believe you are then that is correct yes. You may also have some random harnesses on each bucket that are intended for the meter bridge (if you don't have the meter bridge they would be tucked loose inside the chassis)
Maybe I'm blind, but it appears that ch 1-8 and 25-32 are 8 channel buckets added on either side of a 16 ch board/bucket.
Each channel has a 2 conductor ribbon connection to the master section on the back side of the chassis. What are those? Were they intended to be for the meter bridge that didn't exist when I bought the board?
Yes. They only appear to be going to the master section, but if you were to cut all those ties you'd see they're just a single split up ribbon cable that feeds each section of the meter bridge.
The big ribbon appears to be located right below the channel assign section. (one of my issues) Should I remove it and de-ox all the connections? Or is my problem in the master section?
It is unlikely you're going to need to de-oxit every pin on the ribbon unless the desk was stored somewhere particularly damp for a legthy amount of time. Both the plugs and sockets have gold plated contacts. A minimal amount of oxidation may be present but pulling and reseating should be enough to wipe that clear. It's also unlikely that a single dodgy channel contact would manifest as a whole master output side being low. My guess is that you're looking at something in the master section. The pots are notoriously dodgy on these, and the board is full of really cheap no-name electrolytic caps in the signal path. Additionally all the op amps are socketed, and they're milled socket contact- which is great- but, that doesn't mean the IC pins haven't built up corrosion in the sockets. you may find success in pulling and reseating the ICs on the master card (it can't hurt) and potentially re-capping the master card.
If the desk has been around a while, it also may not hurt to pull the main fader apart and give it a clean with isopro. The fingers on the wipers do oxidize and a drop of deoxit (for god's sake don't spray it) on the wiper fingers under the carriage goes a long way also. See expanded description below.
Thanks to this site, I've learned that finding the schematic is nearly impossible, so even if I take it apart I still don't really know exactly what I'm looking at. I am loath to take it apart any further as you might guess. I'm really not a bench jockey, I know just enough to break something with a misstep.
I may be able to assist. Please send me a PM.
I'll be cleaning all the i/o's on the back as a matter of course. This board has lived its entire life coupled to a RADAR, and all those cables will be cleaned as well. Should I just buy a case of Deoxit and give it a bath?
Another thing I noticed is that there seems to be a lot of micro-switchs on each channel. What am I looking at?
As far as Deoxit goes- your absolute best method, both for cost/waste, and for ease of use and not getting crap everywhere:
Get some Deoxit D100 liquid in the glass vial. I usually buy the 60ml jar. I get a needle-dispenser bottle and dilute the D100L to 20% with 99.9% isopro. You waste WAY less product, and the isopropyl is safer across more surfaces and substrates than the naptha based solvent in the spray.
My last question for today: can I effectively clean the faders without pulling each channel out? Or are they sealed? As slow as I am I don't want to waste time pissin' up a rope.
Yes. You can pull the faders independently of the channel cards. Two screws connect the fader to the panel, and then a header clip connector comes out and the fader assembly pulls out. At either end of the fader shell you'll see that the end tabs clip onto the edges. A small screwdriver and a gentle twisting motion will shuck them like an oyster.
Hit the whole thing generously with 99.9% isopro, to flush it. You will probably see some greenish gunky grease that has dried up and trapped all kinds of gross crap. Gently use a toothbrush and some of the iso alcohol to work that gunk out and wipe down the fader rails. With a clean qtip or bit of paper towel wipe the carbon track with a generous amount of iso. A flush after doesn't hurt. A drop (a
DROP) of deoxit on the fingers as previously mentioned- you will probably see they have a 'rainbow' like appearance if you look under the carriage.
Important: there are two sets of fingers- one well hidden under the carriage. The hidden set is the active wiper on the mono faders, so don't miss it!
You can also see there are some metallic traces at each end of the fader that the wipers 'land' on at both ends of the travel- these are also likely oxidized. You can see a before and after- you will probably need to give these a light scrub with a qtip and some iso.
Last step, get some light silicone shock oil from your local RC hobby shop (I use 50wt. for an almost frictionless feel, or 2000wt. for something with a little 'push' to it) You want to be
VERY sparing with this and careful not to get any on anything else- it's an absolute bastard to clean the residue of heavier silicone oil! A couple pin-head sized drops on either side of the carriage on the top rail. The bottom rail can be left un-lubricated, or you can put just the smallest amount of silicone on it. If you can't find silicone shock oil locally or on amazon, DON'T use regular household oil. It'll gum up over time. Sewing machine oil is an ok substitute.
As you may be able to tell I've done a couple of these before.... Got one 32 ch beast here right now!
