PL400 newbie

dobrojim

New Around These Parts
Joined
Jan 18, 2021
Messages
2
Location
Reston, VA
#1
Hi everyone, total newbie here. Back in the 70s I became familiar with PL400 as a neighbor had included one for the killer stereo that had put together. I remembered that amp ever since. Very recently a well to do friend had grown tired of what he presumably considered clutter and gave me a pair of PL400 amps which he had lying around in is house unused. So now I'm trying to figure out what to do with them. They are now at a repair shop for a guy I trusted with a Fender tube guitar amp repair. His preliminary effort is that one of the 2 amps, powers up okay but one channel is low on power. The other amp has DC output in one channel. Both appear to need meter and/or lamp repiar. I guess I should read through the intros below as I am unsure what to do with these PL400s (I believe series I). I don't really need them but I recognize the potential and/or the possible value if sold (or repaired and then sold).

Maybe one important thing to ask the community is a recommendation for a repair person, ideally near Wash DC.

Or alternatively, a source for the service manual and schematic.
 
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mlucitt

Veteran and General Yakker
Joined
Jun 24, 2011
Messages
2,501
Location
Jacksonville, FL
#2
Your experience (as related by your technician) is typical of these 40-50 year old amplifiers. The difference between Phase Linear and any other amp of that vintage is that Phase Linear built them so they could be updated and brought back to life. These amps should not be powered up until they have the power supply capacitors replaced. Also, they should not be connected to speakers because of the tendency to place DC on the speaker outputs.

You can do the upgrade yourself if you are handy with a soldering iron. Or, there are technicians in Virginia that will help you get those amps restored better than factory new. The answer you are looking for is White Oak Audio Design. The website is here:
https://www.whiteoakaudio.com/estore.aspx

This forum has a library section and you will find your documents there. Also, do a search on PL400 rebuilds, you will see that you are not alone.

Welcome to this site. You will find great support here. Tell us a little bit about yourself, and attach some pictures of your PL400 amps.
 

dobrojim

New Around These Parts
Joined
Jan 18, 2021
Messages
2
Location
Reston, VA
#3
Thanks for the welcome and reply.

The advice not to power up was something I was also warned against when I decided to dust off my Fender Bandmaster (mid 60s era).
My understanding is the electrolytic capacitors degrade simply from idle storage and will smoke and/or catch on fire
if one attempts to power up after a long period (in my case it was 15-20 years) of sitting idle.

So anyway my thinking now is that perhaps I should go ahead and have a re-build done on the one PL400 I have
that is in semi-working condition. It sounds like that one may need one or more new output transisters given
the discrepancy in output between the channels. That's in addition to the need for the kit that basically does
a re-cap repair/enhancement. BTW, that amp had a toggle switch installed on the front as a previous owner
wanted a direct way of powering it up and down.

The two amps are almost a 3 hour drive from me at my technician's house near Redding PA. So
I won't be able to provide pix until I go back up there.

A little more about me - emergency logoff, wife needs computer. WIll add more later.

So my background - retired biologist from 28 years of federal service with NIH, something I am most
grateful for. My specialty was DNA sequencing. Going back long before, grew up in DC area, started
playing guitar at age 10, started riding motorcycles at age 13/14 (in the dirt). Raced MX for a number of
years. Now have a Beemer road bike (05 R1200ST) but honestly, I don't ride it that much anymore.
Didn't really get completely serious about playing music until much later and now play guitar, dobro,
weissenborn guitar and sing at times. Built knightkits and heathkits when I was barely 10 or so. Ten years
later built the Hafler DH-101 preamp I still use in my system. Married to the same wonderful woman since 1990.
Two kids, both now college graduates.

So yeah, re the PL400s I was gifted, I guess the main question in my mind at this point is
which kits to get. The meters have issues. The caps and transistors are all old, closer
probably to 50 than 40 years old. So all that should be replaced.

It's great to find a community which can offer support and the wisdom born of experience.
PS- my father was an electrical engineer but while I understand the function of individual
parts, I don't have the first clue about how they all work together. So I leave that to people
who do understand such things.
 
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WOPL Sniffer

Veteran and General Yakker
Joined
Aug 10, 2015
Messages
6,637
Location
Arizona
Tagline
Screw it
#4
"It sounds like that one may need one or more new output transisters given
the descrepancy in output between the channels". ??????????


If it's 40 years old..... Replace it.
 
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