Yamaha PM700 my retirement console mods

[dirtbikeman11]

Hi everyone, I’m settling in on this newly acquired pm700. I plan to mod it to suit my needs. It’s very clean and after replacing 2 fuses inside it seems to work, except for the right VU program meter.
1st up after testing and cleaning will be to move the power supply outside of the box, to make room for the future direct out transformers. I believe there’s +-22v, +-15v, +12v,+6v. There are 15 wires carrying these dc voltages into the console.
Should I just get a 15 conductor shielded cable and build a box for the ps , housing all the pieces I have already? Or look for a beefier power supply that can accommodate all the voltages I need? Thanks in advance.

 

[dirtbikeman11]

 

[dirtbikeman11]

 

[dirtbikeman11]

Here’s a picture of the backside of the power supply board, looks like I can cut down on the number of wires from 15 to 12 in the cable and double up on some of them. Maybe use a dB 25 connector? Or is there something better? I’m very new at this. So any advice is welcome. Also there are other wires coming off the transformer not being used, do you think there would be 48v available in there? There is no phantom power in the stock mixer. Thanks Mike.

 

[sodderboy]

On my bench, I would add P48 in the external PSU, just like any huge console. Make it switchable on the back of the desk, low-profile toggles? I don't know the panel. Master OFF also, just because.
To connect, the dsub contact area is too small, even if triped-up. I like the AMP CPC connectors, Series 1 and 3, handle higher power and you can double pins. I pick the shells for the job. I would go 10 Ga on the 0vl and chassis (looks like no chassis wire to modules?*), 12 Ga on the +/-22, 14 on the rest. I don't know the power consumption, so maybe I would gauge lower for all, 12, 14, 16, it depends also on the length of the cable. Use the same size wire as the cable inside each chassis, replacing the original. If they are doubling smaller wire to save production cost, replace with bigger. Expando sheath over it and you have a monster!
* There is a lot of metal in there, so they must have it bonded and connected to mother earth somehow? Not familiar.
Mike

 

[dirtbikeman11]

Thanks Solder Boy, there are 5 fuses in the power supply. 1.5 amp to 1.0 amp. Does that give us an indication of wire size to use? I was hoping to find a 12 conductor cable that I could buy around 8’ and a multi pin connector like you suggested. Great idea on the phantom power being on the back panel. Why didn’t I think of that.

 

[dirtbikeman11]

Ok, so I removed the power supply to a separate box and bought a 48v ps to get phantom power into it as well. Tested the console again and everything that was working before, still does. I’d really like to fix the vu meter before I move on to more mods. It lights up but no needle function. This is the right main meter. I don’t know how to even access it? Does anyone have any experience with this? I swapped the L & R main channels but that didn’t work. Any ideas?

 

[NOON]

I'd suspect the cabling or the driver circuit before the meter itself, it's quite a complex path with quite a few failure points. Also double check the connection to the meter itself, I think mine stopped working at one stage and I just tightened some nuts to fix it. I've heavily modded one of these desks and it's a beast now. They're great even stock though. I'll do a post about everything I did when I get time.

 

[dirtbikeman11]

That would be great to see the mods you did. After I get this meter thing figured out I’m going to add direct outs on all 12 channels.maybe put a pull switch pot to replace Mon 2. Pull on to enable direct out, push in for stock Mon 2 send. It works in my head.

 

[radardoug]

Why do you need a switch?

 

[dirtbikeman11]

I heard pulling the direct out off the Mon 2 pot was a good place. Instead of loosing the Mon 2 pot as stock, I could switch back and forth as needed. Anyway I think I screwed something up when I removed the program meter bridge, swapped meters and put it back, now neither meter works and the console barely passes audio. I’m in over my head I fear.

 

[saulpickett]

I heard pulling the direct out off the Mon 2 pot was a good place. Instead of loosing the Mon 2 pot as stock, I could switch back and forth as needed. Anyway I think I screwed something up when I removed the program meter bridge, swapped meters and put it back, now neither meter works and the console barely passes audio. I’m in over my head I fear.

sorry to revive a dead thread. I'm jus saying. Probably a ribbon cable. Also. The mon 2 pot isn't a great place to pull a direct out to an unbalanced 1/4" jack actually. Turns out. Super noisy, etc. I made some little spade connectors or something that attach to the Mon2 point on the Cue switch? Or something. But. I'm not a big fan of this being the direct out.... the unbalance and all that just adds a ton of noise and crosstalk , connecting these channels in the middle by the parasitics,etc, even with all direct out jacks unplugged. that said, I haven't tried it transformer isolated; surely you would need a separate buffer to drive the transformer (like another opamp or something, etc .) otherwise you would be shorting that point to ground ,etc.

edit: I think there are a ton of issues with this model. PM-700. Still haven't wrapped my head around it or even looked at the circuit in a long time, but I get the feeling I remember there being WAYY too many resistors to ground or just murking up the circuit near the input? The other thing I almost remember, is thinking that the input transformer should be reversed, rather than the direction it is depicted in the schematic. i've messed around with this board quite a bit; and I think its just really hard to crack the code and make this thing "what you want it to be..." Clean, huge, overpowered. It seems like all the correct components are there "for magic to happen.." but honestly, I think the cards themselves were either a miss, or just designed for a different period of time and equipment we aren't used to. Anyway. Thought I'd just pop in and mention this. PM-700. What a dog. I think it can be brought to life, but honestly, I've been scratching my head over this board for a few years now and done some stuff to it... I think there's potential but its really a bit non-trivial if you ask me. The next thing I really want to assess: is removing as much "resistor junk" off the circuit as possible, and flipping the transformers around, devoting the console to probably more of a line in anyway. idk. Its so frusterating because the whole thing is built well and looks great it just performs so poorly.

edit 2: hmmm. I remember now I made 8 pin to 7pin opamp converter boards for this. so not worth it. you need original 7 pin or honestly the stock chips are fine. as far as the dead meter goes , such as the guy in the original post, those meters go open and are essentially impossible to repair, regardless of the driver circuit. man. I really wanna crack the code on this board because I've gone a ways with it but there's still a ways to go. maybe next year?