Cuts affected by Total Recall

[billythekid]

Hey all, I think I'm getting close to chasing this problem down, but am having trouble locating a schematic for a G Series Keyboard Interface. On one bucket in particular, I'm having phantom cuts turn on and off intermittently (regardless of being in or out of Total Recall). There is definitely a correlation between the total recall and this problem. 

In my videos you can see how the cuts are affected by the LEDs in the fader status portion of Total Recall. For what it's worth the total recall is not working correctly at the moment either. It's now showing all channels as being turned fully clockwise. And now two of the faders in the bucket are not responding, and being read on "Faders to Meters" even though all faders are down. Swapping out faders made no difference.

Links to a video of the problem:
-http://youtu.be/YYx-mNMTJrk
-http://youtu.be/B3Hg8bZHoq0

[sintech]

The Total Recall is on input, so you have an issue with the TR bus driver side of this combined G keyboard interface.

The circled fusing resistor, is that a burnt?

[billythekid]

The resistor itself actually looks ok, but the PCB is pretty fried around it. Next time I have it in front of me I'll be checking that resistor, but I'm a noob when it comes to tech-ing. Anyway you can explain what you mean by the TR bus driver side of this card?

If the resistor checks out, would it make sense to think it could be the PCB trace?

If there's anything you'd suggest I try or any information I can give to maybe gather some help, would be very much appreciated!

[sintech]

Yeah, now see what you mean by the cuts affecting the recall.

What's happening, the TR is on input, it's not seeing the Bus Driver part of the circuit, but still connected to the large fader.

So when you cut or move the fader top to bottom, all the TR objects will move from anti-clockwise to fully clockwise (or something like that)

The TR circuit repurposes the large fader lines when playing a setup, so hence why it's all related.

[sintech]

Attached is the circuit. it’s very easy to short this out by pulling channels in and out of a powered down bucket, whilst leaving the centre section turned on.

The three resistors TH1-3 fuse the power inlet.

Active parts:

The TR connections are isolated via Optocouplers  (IC 7-15)

IC 16-17 Logic

8x BC212LB

[sintech]

So this part of the PCB, that looks good. So really the first thing to do, is check you have power.

[xmax]

I had a similar problem, it turned out to be the 50 way ribbon on that bucket. But maybe not in your case. N

[billythekid]

Thank you, thank you, thank you! I truly appreciate the suggestions and the energy you've put into helping. My gut tells me it's going to be a problem with TH1-3. I'll be checking there first thing tomorrow. Then look for power on the part of the card you suggested. And then will verify the 50 way ribbon on the bad bucket is all good.

I hate to keep asking for more help, but can you explain how I'd actually go about testing by pulling the channels in and out of the powered down bucket while the center section is on? Sorry for being so thick, I have no background in EE, normally I make music lol

[billythekid]

Would there be a specific reason why there is only one bucket's cuts acting weird? Like would a specific TR Bit correlate to a specific bucket? Or something along those lines? Don't know if that's a really dumb question to ask :/

[xmax]

Swap the ribbon to another bucket, it will at least confirm where the problem is. If it moves with the ribbon
the problem is in the ribbon or computer, if it stays in that bucket then your problem is in that bucket.
There are several places you can swap the 50 way, you will see one goes from the bucket to the main
connector panel then from that panel to the computer. N

[billythekid]

And hopefully last questions, after googling schematic symbols, it looks like TH1 should be a thermistor and it looks like there is currently a resistor in there. Could that be the problem? Or does it not matter? Since the revision is blank, maybe I have an early revision before they changed it to a thermistor because of failure? I want to replace the it and don't know what to replace it with, a 10 ohm carbon resistor? Sorry for all the questions!

[sintech]

Looks to be a standard 10R here.

[waltzingbear]

in my experience, lots of the thermistors were changed to 10R resistors at the factory. ie deemed unnecessary.

that has obviously burned out before, you should check continuity of the supply to a few points it feeds to make sure it hasn't vaporized a trace somewhere. Do you know if this was working after the previous resistor was replaced?

But don't focus too much on this resistor, if the board has the proper voltage on it after this resistor, than that is not a problem. This resistor is there to form a small high pass filter in the power distribution system, ie isolate the cards from one another in terms of noise.

Alan

[billythekid]

Thank you for the replies!

Alan - Had this same issue back in September, we replaced that resistor because it looked fried. Everything worked perfectly until just recently.

The TH1-3 resistors are all reading 10ohms and there's power on the active components. I cleaned up the fried area and added a jumper from BICC1 to TH1 bc the trace seemed suspect and now have Total Recall working. Unfortunately the original problem is still there. Cuts continue to be affected by the Total Recall as in the videos initially posted.

I switched out the 50 way ribbon on the bad bucket with a good bucket. Problem stayed with the bad bucket.
Switched the bad bucket's fader modules with a good bucket's. Problem stayed with the bad bucket.
Switched the bad bucket's fader bus card with a good fader bus card. Problem stayed with the bad bucket.
Switched the bad bucket's channel modules with a good bucket of channels. Problem stayed with the bad bucket.
Switched the bad bucket's channel to fader ribbons with a good bucket's set. Problem stayed with the bad bucket.

So at this point I'm pretty lost lol Is there anything else I can switch out to try and narrow it down? Can I swap out the PCB that holds the channel modules? Does this sound like it could be a ribbon?

Seriously would very greatly appreciate any and all suggestions.

[waltzingbear]

you haven't swapped out the computer section. ie, move the 50 way to another slot.

you haven't swapped out the motherboard. I know not real, but it does lead to the suggestion to check very carefully the traces on the motherboard, particularly the power supply races in that area. The function of the logic relys on the difference between 18V and 11V rails, if something is affecting that locally, all bets are off.

because not much else is left to swap!

Alan