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Sorting a Perreaux PMF 1050

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ET16

Super Member
I'm going through a Perreaux PMF 1050 amp. Unfortunately, there is not much info on these.

I was hoping to set the DC offset and bias, but I'm not sure of the pots and whether the resistors I see near them are emitters.

I'm also wondering about the main caps. There's nothing wrong now, but I was hoping to go up to 18,000uf from the present 15K. So far I've haven't found any replacements, as they are very short (50mm).

Any ideas?
 

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Mosfets so no emitter resistors.

On it's big brother the PMF-2150 the channel idle/bias current is adjusted using an inline mA meter in place of the + rail fuse. I assume the procedure is the same for the 1050.

Any wiggle room on the cap height? I found a 50mm dia by 63mm high at 15,000uF 100V.

It appears there is room in the left front of the chassis where you could mount some clamps to the chassis and hard wire the caps to the PC board if you had to.
 
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mrk229 said:
Mosfets so no emitter resistors.

On it's big brother the PMF-250 the channel idle/bias current is adjusted using an inline mA meter in place of the + rail fuse. I assume the procedure is the same for the 150.

Any wiggle room on the cap height? I found a 50mm dia by 63mm high at 15,000uF 100V.

It appears there is room in the left front of the chassis where you could mount some clamps to the chassis and hard wire the caps to the PC board if you had to.
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Thanks for the replies.
Sounds similar to a B&K ST202 I had. Which fuse would I pull? And which pot would do the trick?
 
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ET16 said:
Thanks for the replies.
Sounds similar to a B&K ST202 I had. Which fuse would I pull? And which pot would do the trick?
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On the 2150 it is the B+ rail fuse. And I can't say which pot is the bias/idle current or what the correct current would be for the 1050 amp.
 
Apologies in advance. I don't know how to say this without sounding like a jackass but here goes. If you don't know how to determine which fuse is for the B+ perhaps you should not be messing around inside this amp.

Like @tarior said those output devices are pure unobtainium, I would hate to see you accidentally destroy them.
 
To elaborate further. If that amp is working, I would strongly recommend not messing with it. The very most I would suggest would be to make sure the screws that hold the outputs to the heatsinks are tight, and that there are no cracked solder joints on the board. That's it. I wouldn't touch the bias or anything else.
 
I bought an 1150B 5 years ago and I have nothing but praise. I rebuilt the whole amp all in stock mode. One of the best sounding power amp I had. Its amazing to run this with the Vincent SA-T7 preamp.
2 weeks ago I bought a 1050. Component wise its the same besides its slimmer and A/B speaker switching. I'll be rebuilding this in the up coming months. I thought I'd chime in so I can follow-up with biasing specs.
 
@ET16 ,my advice is to leave it alone. Unless the amp is out of spec, people should stay out of the Perreauxes.

The Hitachi MOSFETs are only available now from scrapped gear. And all the transistors in every Perreaux are hand matched. Do not go replacing them unless they are dead. The caps are very high quality and I think I've only ever come across one or two in 40 years that needed anything.

They are a great sounding amplifier, right from the babies through to the big 5150b/5550, apart from all of them suffering from low level mains. Hum and noise wasn't their best attribute. Basically they are all pretty much the same, just higher voltages, more devices, the further up the range you go.

PS. Your 1kR trimpot is bias (measured over fuseholders with a DCmA meter) and the other should be a 100kR trimpot. It is NOT for DC offset. It is for 20kHz (HF) distortion nulling. Do not touch it. You need to drive the amplifier to rated power at 20kHz and trim the distortion null to less than 0.009%. At that power level and frequency, just the movement of a test lead will throw your distortion out the window. And at that level and frequency, you only have a few seconds before you start burning up the Zobel.
 
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It happen to me when I built my very first 100 watt mosfet amp out of the 1982 Electronic Enthusiast magazine. I traced the board from the magazine page and built the whole thing from scratch. On the final setting I didn't know the bias setting were tricky enough I can't stay longer on idle with the wrong setting. From the J transistor shorting probably up to 3 components. It ran quick.
After I was done with the project, that amp was 10 times better than our 35 watt panasonic consul. Even after years and I went to tubes, if I go back to solid state, I always have a soft spot on Mosfets. That's why I bought the Perreaux. Looking at the circuit design, it looks pretty much the same as the one that I built back 40 years ago. And last 4 years ago I had a chat with one of Perreaux design engineer. It sounded like he was doing the same in the beginning but he ended up re-designing his dad Perreaux, improved it and the rest is history.
 
tarior said:
To elaborate further. If that amp is working, I would strongly recommend not messing with it. The very most I would suggest would be to make sure the screws that hold the outputs to the heatsinks are tight, and that there are no cracked solder joints on the board. That's it. I wouldn't touch the bias or anything else.
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Why not..? That unit is a 2nd generation Mosfet thats 40 years old.
I know there is 1 certified Perreaux service center in the US, I have his contact # somewhere because he did my PMF 1150 which is basically the same in the early hulk package.
I remember he did the whole works on mine. Total recap. Not even 500 bucks. Very Happy!
 
ET16 said:
Was it Precision Audio Labs?
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The 1150 and to the 1050 is almost the same circuit, same hitachi transistors and transformers!
So sorry for the late chime in.... Anyways here is my discussion with Jeffrey at Precision Audio Labs.
I'm not going to disclose an exact number of payments that can cause any misleading. What is important is this guy knows exactly what he's doing with no guessing games.
My personal input is after you get your amp all square up, do not get any of those low-class solid state or tube preamp. Get yourself a real good one that you are comfortable paying. I'm using a Vincent SA-T7 which is not the best but in the top category. With the right speakers, Your system will shine and sound like a $35k equipment with personal long term satisfaction!

Hi,
I’m more than happy to do the work on your 1150B. We don’t distribute schematics to the public and I’m the guy in the US who has done 98% of all Perreaux restorations since the mid 80’s. I’m very sorry, but early on in Perreaux’s history, TV butcher shops started butchering Perreaux pieces almost to the point of destruction, so we stopped distributing schematics. I know your 1150 very well, and I know exactly what goes wrong with them. I also stock the only parts for the PMF-Series of amplifiers in the US. I also have a ton of Perreaux in my system at my home and I love the sound of their amazing amplifiers. Several issues with the PMF series:
· Power switch failures
· Popping, Crackling, sizzling sounds from the left or right channel
· Some of the 1150’s need new power filters. I install audio-grade capacitors that make the 1150B sound better than when it was new. Why? Cuz’ Audio-Grade capacitors were not invented in the 80’s and 90’s.

When these amplifiers arrive at my service center, I replace “all of the parts that go bad over a period of time” and after the service, I issue a One Year Warranty for my work. You’re looking around $*** for the restore, unless your two power filters are bad, which adds another $*** to the total price, bringing you to around the $*** area. BTW the power filters I install are six times taller than those low-boys that are “factory”.

Lastly, because of the TV shop butchery I mentioned above, and because that most guys think they are electrical engineers, I do not give out assistance to DIY guys who are trying to fix their own stuff. If you want her “Better than factory” you can send her to me. The 1150B is one of the lighter Perreaux amplifiers and shipping is not to bad on them. I’m in the St. Louis Metro Area AND I’m about two-weeks behind with Perreaux service, so if you can send her several weeks from now, that would work out.
Please let me know if you have any questions!
Best regards,

Jeffrey A. Jackson
President at Precision Audio Labs
lktrnx@gmail.com
http://www.precisionaudiolabs.com
MSEE, BSCS, Member at ISCET, Member at Society of Broadcast Engineers
IT Domain Administrator, Web Architect, Client-Server Environment Administrator
40+ years experience working on High-End and Legacy Audio Brands: Audio Research,
Conrad Johnson, Bang & Olufsen, Dynavector, JL Audio, Kenwood, Mark Levinson, Marantz,
McIntosh, Naim Audio, Paradigm, Perreaux , Pioneer, Sansui, Sony, Velodyne, Yamaha
Factory Authorized Servicer for North America http://www.perreaux.com/contact
 
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I'm gonna chime in on this threading soon. I have all the recap parts for the 1050. I just need to work on some other projects for now till then.
 
rudolfo said:
I'm gonna chime in on this threading soon. I have all the recap parts for the 1050. I just need to work on some other projects for now till then.
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How did you go, this is my system needs checking over as its been in garage for a dozen years now so won't power up until its checked over; getting back in to enjoying music again now the kids have grown. I haev owned these since the 80's.
 

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My 1050 is back operating again and sounding awsome added a new digital front end Eversolo A8 to go with the Classic preamp and tuner. Its a work in progress will be restoring my Technics SL1600Mk2 turntable next. The second photo is a little blured late night listening session while leaning to drive the streamer.
 

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Oh BTW should add the PMF1050 Poweramp needed a new bridge recitifier, all MOSFETS were fine no caps needed replacing. The Preamp the SX1 needed recapping as some were beyond tollerance.
 

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