Help ! Has anyone repaired a Marantz PM57 Amp ?

[Jack]

I was checking the "idle current" on my beloved PM57 and a freak
accident crashed the right amp - the scope ground lead popped loose
and fell on a component in the circuit and instant smoke ! I was
crushed. I love this amp. Its reproduction is superb. So, I rplaced a
few parts and turned the amp on and more smoke ! What am I doing
wrong ? I am a retired EE with many successful years of design and
building of audio equipment - should I quietly give up ? Someone
mentioned that the "new" Marantz amps are practically impossible to
repair because most of the parts are "selected" when they are built -
Thanks, Jack

 

[N Cook]

Jack <UJackH@hotmail.com> wrote in message
news:d2c17743-b09b-4d0b-aeed-169f028a5ad5@g17g2000prg.googlegroups.com...

I was checking the "idle current" on my beloved PM57 and a freak
accident crashed the right amp - the scope ground lead popped loose
and fell on a component in the circuit and instant smoke ! I was
crushed. I love this amp. Its reproduction is superb. So, I rplaced a
few parts and turned the amp on and more smoke ! What am I doing
wrong ? I am a retired EE with many successful years of design and
building of audio equipment - should I quietly give up ? Someone
mentioned that the "new" Marantz amps are practically impossible to
repair because most of the parts are "selected" when they are built -
Thanks, Jack

magic word "variac"

At least with a stereo amp you can DVM "diode" test between good and bad
channels and remove obvious bad parts. Then gently power up , via a variac,
no speakers, monitoring a few pairs of voltages to home in on some/all ?
remaining obviously bad. Rebuild and power up again via variac , monitoring
a few pairs of votages, etc, When all matches across , connect speakers,
again powering up via variac , increasing volume gradually , still
monitoring a few voltage pairs


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Mark D. Zacharias]

"Jack" <UJackH@hotmail.com> wrote in message
news:d2c17743-b09b-4d0b-aeed-169f028a5ad5@g17g2000prg.googlegroups.com...

I was checking the "idle current" on my beloved PM57 and a freak
accident crashed the right amp - the scope ground lead popped loose
and fell on a component in the circuit and instant smoke ! I was
crushed. I love this amp. Its reproduction is superb. So, I rplaced a
few parts and turned the amp on and more smoke ! What am I doing
wrong ? I am a retired EE with many successful years of design and
building of audio equipment - should I quietly give up ? Someone
mentioned that the "new" Marantz amps are practically impossible to
repair because most of the parts are "selected" when they are built -
Thanks, Jack

I have a PDF of the service manual for this model. It is about 2.75 meg in
size, and I can e-mail it to you if you like, and assuming you can take the
attachment.

(This is a good time to mention to the group that I an changing my e-mail
address for the time being...)

You can e-mail me at:

mark_zacharias@labolgcbs.net

and reverse the domain to read "sbcglobal" and notice there is an underscore
_ between my first and last name.

and I will send the manual.


Also, I have some experience repairing amps and might be able to help with
technical advice.


Mark Z.