Yamaha PM2000 external PSU caps

[abbey road d enfer]

My main concern are the +/- 24V rails. Using the lower trim pot, I was able to get Pin 5 dead on -24V. I was hoping to do the same with the higher trim pot for the +24, but it dosent seem to move from 28 ish volts.

You probably should measure with some load attached.
Typically 78xx/79xx need to deliver minimum 15mA.
IDK about the 24V regs, but it maybe similar.

 

[RoadrunnerOZ]

...and check the trimmer itself. I've seen plenty of trimmers go bad after 40 years.

He actually replaced that along with the 36K - I’m assuming using a brand new one.

 

[Ghaleon]

...and check the trimmer itself. I've seen plenty of trimmers go bad after 40 years.

yup the new trim pot tested fine by itself, so we can rule that out.

 

[RoadrunnerOZ]

You probably should measure with some load attached.
Typically 78xx/79xx need to deliver minimum 15mA.
IDK about the 24V regs, but it maybe similar.

Good point although it appears there’s a 4K7 across the output which may be the inbuilt load for safety.

 

[RoadrunnerOZ]

Worth checking the divider - 620Ω and 10K

 

[RoadrunnerOZ]

It might be worth checking pin for like pin of the positive vs the negative regulator IC. Pin 1 +ve reg, pin 6 -ve reg - can’t seem to find datasheets on the TA7084AM.
I’d also check that the +32V is 32V. TR15 emitter via 10Ω to pin 3 of the regulator.

 

[Ghaleon]

Success It was TR1 - once everything else was checked and TR1 was swapped out, the upper trim pot was functioning again. +/- 24 now dead on.

Thx for all the help guys!

 

[RoadrunnerOZ]

Now - does the console work?

 

[Ghaleon]

Now - does the console work?

The console did indeed light up. My intial test was with 2 inputs/2 masters/TB/FX/FB modules installed. Things are sounding awesome so far

My plan is to go through it strip by strip and identify issues.

I've already recapped and cleaned the faders on 40 strips, still have the TB/FX/FB modules to recap.
I was thinking about starting another thread for issues with the modules? I want to be able to troubleshoot and repair everything myself, if possible

 

[Ike Zimbel]

I'd be surprised if you find a lot of issues with the modules. Probably best to keep the thread here, for now.

 

[RoadrunnerOZ]

Just sold a PM2000 on behalf of a client and it’s been sitting for 3 years in storage - fired it up and working fine. They built these things well and they’re pretty easy to service. I did service on one a few years back for someone who had bought it as is/where is and for its age I was surprised at how little was wrong with it. I’d say if you recap you’ll find little else wrong other than switches needing cleaning and possible wire rot and solder joint failure at wiring junctions - easy to find. Take good photos identifying any wiring locations before tugging at them to test!

 

[Ghaleon]

Ok so first issue has been encounted RE routing

It seems I can't send audio to PRGM 1 (master 1) from any input module. The VU isnt moving, whereas all other PRGM VU's see action when engaged. Tried different input modules, different input module placements on the board, and swapped out different master modules. Cable issues have been also ruled out. Master 1 seems to be the only one effected, all other XLR program outs work.

Also getting some wierd behaviour from the matrix section: MATRIX 1 out doesnt seem to work on any master module. Matrix 2-8 will work on some modules but not others (this could be dirty pots, still need to test more)

I had a peek inside the board, and didnt see anything blatantly obvious (rotting wires, bad solder joints etc). The module/frame connectors seem like they are in good shape, and both sides of the connectors have been cleaned with contact spray and a qtip.

Advice on where to go from here, what to check would be greatly appreciated!

 

[Ghaleon]

Some excellent info buried in another thread, courtesy of @Ike Zimbel

Background info: The PM-2000 channel strips plug into headers that are soldered to backplane boards. Each backplane board takes four strips and then links to the next one over with with bus wire links, about 1/2" (10cm) in length.
What's the issue? Sometimes the solder joints go bad on the links.
How does that show up when using the desk? Typically, a channel will not assign to a bus. So, for example, Channel-1 will not assign to PGM-1.
How to test for this? Pt-1: If, as in the above example, Ch-1 will not assign to PGM-1, the first thing to do is to test to see if Channels 2, 3, & 4 won't either. If they don't, that's a strong indication that you have a bad solder joint on the bussing for PGM-1. If they DO, that rules out a bussing issue and points to a problem on Ch-1 only, like a dirty assign switch, or possibly a soldering issue on its edge connector.
If things point to a bussing problem, the next step is to try and determine where the break is. To do this, move to the last four channels, 21-24 or 29-32 and try routing to PGM-1 from there. If that works, move down to the next four and try them (you just need to try one in each group of four). If it doesn't work, the break is between the last channel and the start of the PGM modules, OR, there is a fault with the PGM-1 module. Swap it with another PGM module and repeat the test. If it works in another slot and the other module doesn't work in the PGM-1 slot, the fault is in the bus wiring as already explained.
Eventually, you will find a point in the desk where above channel "X" PGM-1 bus works and below that channel it doesn't. This will always be a 4th channel (4, 8, 12 etc.) if it's a bus link issue.
Pt-2: Once you have the back of the desk open (remove two very long screws in top of meter-bridge and tip meter bridge back to access) you can use a DMM to measure along the busses to see where the bad joint is.
TIP: Take a Q-tip dipped in isopropyl alcohol and clean all of the bus wire leads before your start metering them. This will remove the film of gunk that has built up on them over the past 40 years and make it easier for your meter to measure resistance quickly and accurately (doesn't hurt to give your meter probes a swab too). You should read between 0 and 2 ohms between most points that you measure. If you see much higher readings, or a reading that won't settle, you've probably found the spot. I went through and re-did all of the upper ones in the pic attached. By re-do, I mean first de-solder the joint, and then re-solder with new solder. In the pic, I'm talking about the row of silver wires down the center of the photo, with each one of those being soldered to the board on either side. Another tip is to use thin gauge solder, so you can quickly do each side without inadvertently re-heating the other side while you're doing the 2nd joint.

 

[Ghaleon]

Update! I got the LED's done for the channel modules and the VU's. Recapped the FB/FX/TB modules as well. Still ironing out the audio gremlins in the board.

On the to do list:

Channel 18 + 19
Channel 18 has popping/noise issues working the PRG buttons, and some weirdness when the PAN + EQ pots are engaged + disengaged. This noise also effects channel 19 somehow

From all channels, PRG 6 button routes audio to PRG 8/master 8, and PRG 8 button routes audio to PRG 6/master 6

Recap phones board

Recap VU meter boards! Add bypass cap?
Brightness adjustment for LEDs - 10V and 16V ***

 

[RoadrunnerOZ]

From all channels, PRG 6 button routes audio to PRG 8/master 8, and PRG 8 button routes audio to PRG 6/master 6

Could be cabling swapped on the insert takeoff to the rear panel, or somewhere there’s a deviation away from the bus lines and a return in the master section. It’s been a while since I’ve worked on one - still not onto the one to be installed. Do the faders for each master work for that master - fader cable swap???

 

[RoadrunnerOZ]

Channel 18 + 19
Channel 18 has popping/noise issues working the PRG buttons, and some weirdness when the PAN + EQ pots are engaged + disengaged. This noise also effects channel 19 somehow

Check the 1K8 resistors on the wiper of the pan switch to ground - one may be open or drifted in value.

 

[Ghaleon]

Check the 1K8 resistors on the wiper of the pan switch to ground - one may be open or drifted in value.

Will check this thanks!

I was also investigating the back panes - it looks to me like they were modified somehow? Traces scratched out etc. I thought that it may have come like that from the factory, but maybe just a bush fix for something? I'll try and get a pic

 

[RoadrunnerOZ]

Will check this thanks!

I was also investigating the back panes - it looks to me like they were modified somehow? Traces scratched out etc. I thought that it may have come like that from the factory, but maybe just a bush fix for something? I'll try and get a pic

Look for any cross wiring to other buses - may have been done as a factory or third party mod though. There were some 2 bus mods done, non factory, but can’t remember what they were for.

 

[Ghaleon]

Look for any cross wiring to other buses - may have been done as a factory or third party mod though. There were some 2 bus mods done, non factory, but can’t remember what they were for.

This problem solved! A real obvious one, much to my dismay.

Updates on the board:

All VU meters have now been recapped
Got a couple more modules working (with Ike's help!)
Further backplane PCB work

Work still to do:

1 input channel still has an issue with the HPF switches - complete roll off below 2 khz when engaged. Channel seem to work fine otherwise

FB1 output is very low. Using a resistance test on the backboard, FB1 from the input channels to the FB module seems fine. On the FB module itself, I worked on the FB1 signal path. I swapped out all the tant caps, and IC 1 + IC 2 + IC 9. No change, still very low output from FB 1 output. You can hear FB1 from the matrix section without issue.

Other than that, I'm starting to look at the eq's if anyone has some guidance. I know about the JLM inductors, and Flying Eye has thier own version of an inductor mod.

I was wondering how much improvement there could be replacing the tant's with film? adjusting Q values and eq points through this method? I haven't been able to find a lot of info regarding this, just that ppl usually choose "neve" eq points, and can achieve this through replacing caps

 

[Ike Zimbel]

You can hear FB1 from the matrix section without issue.
If you can hear/see the FB-1 signal out of a matrix output, it means that all of the FB-1 electronics on the FB/Echo module are good. The fault is either in the output transformer for FB-1, or the wiring to/from the transformer. The metering is picked off just after the transformer, ahead of the XLR, while the Matrix signal is picked off just ahead of the o/p transformer.
Edit: I suppose there's also a chance that just the meter switching is bad...have you actually looked at the o/p from the XLR, or just used the meter to see if it's working?