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Oberheim Matrix 1000 PSU Fix guide Desktop Synthesizers
Old 15th May 2015
  #1
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Thread Starter
Oberheim Matrix 1000 PSU Fix guide

This hopefully will be the definitive guide to solving the dreaded Oberheim Matrix 1000 vibrating PSU issue. I like many others experienced the same issue, and it occurs when the transformer itself makes loud hum noise due to magnetostriction in the core material. Since the circuit is all linear, there are peak haversines of current flowing through the transformer to charge capacitors every cycle, and these peaks can be high enough to get the core laminations moving (if they are not staked well and varnished well) Its also an issue that can (and does) increase over time, as is the case with the M-1000 PSU vibrating like crazy. There is no easy way to quiet that down if it’s happening and a metal clamp (like the often suggested TX81Z fix) doesn’t do much. The only solution is to remove and replace but finding a linear PSU that will fit, is near impossible. The only real option is a switching power supply and one that has multiple voltages. In this case the M-1000 requires a quad switching power supply that can deliver 5V, 12V, -5V, -12, and a bypass of the onboard regulators. I had this work done by a synth tech but even someone with some limited skill could do it (BUT DO SO AT YOUR OWN RISK!!) Still it's pretty easy and shouldn’t cost much to do by any decent electronic technician. Anyway here are the steps and some photos. I got mine done and its glorious. This classic synth is worth the effort!!

Step 1: Use a volt meter and carefully measure the voltage on each regulator listed and on the photos (Make note of each, You will be looking for +5, -5, -12, +12. The attached schematic is very hard to read but you can reference that as well.)
Step 2: Completely remove old power supply and associated hardware
Step 3: Remove 5 regulators (shown in schematic and photos)
- 7805 (x2)
- 7905
- 7812
- 7912
Step 4: Install new PSU (Mean Well PSU RQ-50 - see attached pdf) Cost about $20-30 USD
RQ-50B: 45.5W AC/DC Enclosed Switching Power Supply: Mean Well
Step 5: Use one of the old holes to mount the new PSU our drill your own
Step 6: Apply some adhesive rubber strips on top (to keep case from rubbing)
Step 7: Run wires to each of the matching power points on the board you measured before (Note that you have to run a double wire off the PSU +5v terminal for the two 7805s which each require +5v)
Step 8: You have to run a common ground wire on U7 going back to the PSU (see on photo)
Step 9: Test

Good luck!
Attached Thumbnails
Oberheim Matrix 1000 PSU Fix guide-1.-remove-psu-regulators-m1000-.jpg   Oberheim Matrix 1000 PSU Fix guide-4.-new_2316.jpg   Oberheim Matrix 1000 PSU Fix guide-5.-new_2317.jpg   Oberheim Matrix 1000 PSU Fix guide-6.-new_2320.jpg   Oberheim Matrix 1000 PSU Fix guide-7.-new_2321.jpg  

Attached Files
File Type: pdf 2. Oberheim Matrix 1000 Schematics.pdf (2.07 MB, 536 views) File Type: pdf 3. RQ-50-spec copy.pdf (616.1 KB, 251 views)

Oberheim Noise Test.mp3 (4.90 MB, 4577 views)


Last edited by walterswan; 18th May 2015 at 05:13 PM.. Reason: Listing the correct voltage measurement on board typo (-5v)
Old 15th May 2015
  #2
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Awesome post man, thank you
Old 15th May 2015
  #3
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tux99's Avatar
 

Thanks for posting the details of your conversion, I think I will go down the same route with my Matrix-1000.
Old 15th May 2015
  #4
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autoy's Avatar
I thought this problem did not affect white-faced Matrix 1000 but the OP seems rather white. Can anyone confirm this is a general problem with all units? For future purchase interest, mainly.
Old 15th May 2015
  #5
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Thread Starter
I used a photo of a white m1000 to show what to remove but psu type isn't different so it shouldn't matter. I have seen reports of it occuring on both.
Old 15th May 2015
  #6
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mrdazobee's Avatar
 

Going to try this.Thanks for the detailed info!
Old 15th May 2015
  #7
Gear Head
 

Switching power supplies can be electrically noisy, and the Matrix wasn't designed to work with one (so doesn't have filtering for it). Any audio noise problems that you've noticed with the new supply?
Old 15th May 2015
  #8
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Thread Starter
Quote:
Originally Posted by grenert View Post
Switching power supplies can be electrically noisy, and the Matrix wasn't designed to work with one (so doesn't have filtering for it). Any audio noise problems that you've noticed with the new supply?
Actually I am very impressed how quiet the unit is and can't hear any electrical noise on the output. The noise floor is very faint or even less than that. And the tech that did the mod for me remarked of the same. I could run some recordings of it with a couple factory patches so people can hear it. I've played it now for a couple other m-1000 owners and they were impressed as well. So all good on that Mean Well PSU at the very least.
Old 17th May 2015
  #9
Gear Head
 

Great to hear! Thanks for sharing it with everyone.
Old 17th May 2015
  #10
One might simply just replace the power transformer with a torridal or rebake the original transformer....
Old 17th May 2015
  #11
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tux99's Avatar
 

Quote:
Originally Posted by kazper View Post
One might simply just replace the power transformer with a torridal
I looked into that some time ago but I struggled to find one that had the required dual output at the right voltages and fitted into the rather narrow space inside the Matrix-1000.
A custom made one would probably cost too much (but I didn't look into that as I wouldn't even know who to ask about that).
Old 17th May 2015
  #12
In the U.S. It seems harder to get something like that done for sure. In another thread some of the EU guys was saying that it's fairly easy to have custom stuff done or have the original transformer repaired fairly local often.

Nothing wrong with the modifications overall except those PSU need some cooling means. Did you look at the specs to make sure that it's attiquate in the space and don't require a fan?
Old 17th May 2015
  #13
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Thread Starter
Quote:
Originally Posted by kazper View Post
In the U.S. It seems harder to get something like that done for sure. In another thread some of the EU guys was saying that it's fairly easy to have custom stuff done or have the original transformer repaired fairly local often.

Nothing wrong with the modifications overall except those PSU need some cooling means. Did you look at the specs to make sure that it's attiquate in the space and don't require a fan?
Yes, of course. The PSU uses free air convection to cool and it doesn't break a sweat in the M-1000 case. Currently its running about 74 F/22C, but its rated up to 158F/70C. When closed the case is cool to the touch after being on 4 hours. I have attached the specs of the PSU in the first line of the post. I imagine there are others out there but this one checked all the boxes for me.
Old 17th May 2015
  #14
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Thread Starter
Quote:
Originally Posted by grenert View Post
Great to hear! Thanks for sharing it with everyone.
I attached a MP3 of a quick recording to the thread attachments, going through a few patches starting in Bank 2. I left space at the beginning, end and between patch changes. Its a raw recording into an Apollo. At the end I add reverb on the Apollo patch...just because. ;-)
Old 18th May 2015
  #15
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Quote:
Originally Posted by kazper View Post
In the U.S. It seems harder to get something like that done for sure. In another thread some of the EU guys was saying that it's fairly easy to have custom stuff done or have the original transformer repaired fairly local often.

Nothing wrong with the modifications overall except those PSU need some cooling means. Did you look at the specs to make sure that it's attiquate in the space and don't require a fan?
a switching supply will be far more efficient and by virtue far cooler to operate in a cramped space. as long as you use some filter caps on the output rails you should be fine as far as noise suppression. there are crappy switching supplies that have more noise and ripple on the rails than quality ones so test the rails with an oscilloscope first, not just a multimeter.
Old 7th September 2015
  #16
I have just done this mod with my two Matrixes - works like a charm! :-D
Thanks for finding this power supply, fits right in.

I had to change the fuse to something much bigger because even though it was a slow blow it couldn't stand the big power-on current of the Meanwell.

After switching on the first one, I thought I had ruined it because it didn't react and just showed the firmware version. The solution: it was doing the calibration routine (just wait a minute!) because I had changed the battery while I had it open. Phew! ;-)
Old 7th September 2015
  #17
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Quote:
Originally Posted by Mesmerised View Post
I have just done this mod with my two Matrixes - works like a charm! :-D
Good to hear another positive report about this conversion.

What fuse did you use instead?

I still haven't done mine due to lack of time but one day I will do it too.
Old 12th November 2015
  #18
Gear Head
 

Quote:
Originally Posted by tux99 View Post
Good to hear another positive report about this conversion.

What fuse did you use instead?

I still haven't done mine due to lack of time but one day I will do it too.
I'm curious to know about the fuse issue, as well, as I'm about do to this conversion..
Old 12th November 2015
  #19
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Quote:
Originally Posted by madmaxmarchhare View Post
I'm curious to know about the fuse issue, as well, as I'm about do to this conversion..
I didn't have any fuse issue to speak of, I only changed the PSU. Been running 7 months now nearly every day.
Old 12th November 2015
  #20
Gear Head
 

Quote:
Originally Posted by walterswan View Post
I didn't have any fuse issue to speak of, I only changed the PSU. Been running 7 months now nearly every day.
Thats good to know. I'm not sure why it would be an issue, but since someone mentioned it.

I wonder if it would be easier just to cut the posts to the regulators rather than removing them from the board? Also, is it correct that the center post on the regulators is the shared common?
Old 12th November 2015
  #21
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tux99's Avatar
 

Quote:
Originally Posted by madmaxmarchhare View Post
I'm curious to know about the fuse issue, as well, as I'm about do to this conversion..
Mesmerised replied to me with regards to the fuse type on VSE here:
problem with Oberheim Matrix 1000 - Page 2 - Vintage Synth Explorer Forums

Quote:
Well, I just went higher with what I'd got. I think I ended up with 1,8A slow blow. (on 230V, that is) 1A didn't quite cut it.
Let us know how your conversion went once you have completed it.
I have the MeanWell PSU here but haven't done the conversion yet.
Old 12th November 2015
  #22
Gear Head
 

Quote:
Originally Posted by madmaxmarchhare View Post
Thats good to know. I'm not sure why it would be an issue, but since someone mentioned it.

I wonder if it would be easier just to cut the posts to the regulators rather than removing them from the board? Also, is it correct that the center post on the regulators is the shared common?
Ah.. ok.. downloaded the schematic.. makes sense..
Old 12th November 2015
  #23
Gear Head
 

Let us know how your conversion went once you have completed it.
I have the MeanWell PSU here but haven't done the conversion yet.[/QUOTE]

Thanks for that info. If the fuse becomes a problem, I'll let people know. Should I film me doing the conversion? Would that help anyone?
Old 12th November 2015
  #24
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Thread Starter
Quote:
Originally Posted by madmaxmarchhare View Post
Let us know how your conversion went once you have completed it.
I have the MeanWell PSU here but haven't done the conversion yet.
Thanks for that info. If the fuse becomes a problem, I'll let people know. Should I film me doing the conversion? Would that help anyone?[/QUOTE]

Hey there, Not sure about cutting the regulators since my synth tech opted to remove them. The common was run from U7 but I would double check the schematic too. I am sure people appreciate a video.
Old 12th November 2015
  #25
F5D
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Thank you very much for sharing this information!

I have already recapped my whole M1000 3 years ago and replaced the battery with a new one + a holder at the same time. Mine does not vibrate, but of course it runs quite hot, so swapping the PSU might be a good idea to give the module more lifetime due to running cooler. Those of you who have swapped the PSU, how warm or hot does it run, when the enclosure is closed, still at room temp? Probably the linear regulators cause all the heat in the original psu. I have not checked how much the synth pcb generates heat.
Old 12th November 2015
  #26
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Thread Starter
Quote:
Originally Posted by F5D View Post
I have already recapped my whole M1000 3 years ago and replaced the battery with a new one + a holder at the same time. Mine does not vibrate, but of course it runs quite hot, so swapping the PSU might be a good idea to give the module more lifetime due to running cooler. Those of you who have swapped the PSU, how warm or hot does it run, when the enclosure is closed, still at room temp? Probably the linear regulators cause all the heat in the original psu. I have not checked how much the synth pcb generates heat.
This PSU uses free air convection to cool and it doesn't break a sweat in the M-1000 case. It runs about 74 F/22C even after on for an entire day. I am still quite surprised how quiet it is, both internally and its output.
Old 13th November 2015
  #27
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mixergod's Avatar
Just completed my upgrade here. After 13 years with a loud hum, resulting in severe under-use of the device... that's a huge relief. Also with the upgraded OS 1.16 and the new Detune, it easily stands up to some of my other polys.

Thanks 1000x @walterswan!!
Old 13th November 2015
  #28
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How similar is this to the power supply for the Xpander? I'd love to do this for my vintage Oberheim.
Old 13th November 2015
  #29
Gear Head
 

Can someone (perhaps OP) tell me where the black and red/black wire are going? Are they grounded to the case (away from the power supply?)? The picture just doesn't quite give me the amount of detail I'm comfortable with..

Old 13th November 2015
  #30
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synthdood's Avatar
Looks like they go to the power switch on the front.
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