Carver PM-1.5 Amp Help

[bytraper]

Hi everyone,
Its a stereo amp thats supposed to deliver 450W rms per channel into 8ohms.

One channel (right) is very quiet but I can just hear it through the speaker
I have attached, the second channel is louder but not by much Im assuming
the amp is blown somwehere, does anyone know any common faults that would
cause this in this particular model amp or have any idea where I should
actually be looking?
I can provide photos if that will help.

Also would anybody have a schematic diagram for this?

Cheers!

 

[[email protected]]

bytraper:
Get your DMM out and take voltage measurements in the power supply and
make some component tests, primarily the semiconductors, low ohm
resistors and electrolytics in the audio power output/driver stages.
Also, be certain that you have not forgotten to jumper the preamp
out/main in connections if there are any..... and make sure that all
the switches are in the correct position and a tape monitor or adaptor
switch is not left on.
The good news is that because a stereo amplifier has duplicate
circuitry in the Left and Right channels you can easily make circuitry
comparisons. It would be unusual that BOTH channels would have
exactly the same failures so be certain to look at the things that both
channels have in common like the power supply and the switch positions,
etc.
electricitym
..
..

 

[Bruce Esquibel]

[email protected] wrote:
: bytraper:

: The good news is that because a stereo amplifier has duplicate
: circuitry in the Left and Right channels you can easily make circuitry
: comparisons. It would be unusual that BOTH channels would have
: exactly the same failures so be certain to look at the things that both
: channels have in common like the power supply and the switch positions,

The bad news is the Carver stuff from that era didn't use conventional
designs and the above would probably not apply.

Most of his amps were rated from 350 to 600 watts rms but the heaviest of
them was probably around only 20 pounds. The power supplies in those were
very unusual (named magnetic field) compared to standard amps and likely the
problem with the amp is related to that.

Although hunt and peck might work, this is really one peice of hardware one
should have the manual on, at least the schematic to examine the power
supply portion of it. The "grounds" on those amps should be particularly
noted. It's not a hot chassis like modern day tv's are but the rail
voltages (from memory) aren't taken from what you think is ground. More of a
reference voltage from that triac thing to other points.

Anyway, scout around ebay, there is usually a guy on there selling the
manuals for those things. Probably photocopies but should be under $10.

Note that these amps had dozen of circuit mods made to them at the factory
and chances are none of the "factory" schematics show them. Also I haven't
checked recently but parts for the exotic stuff were next to impossible to
get even just 5-6 years ago. Think Bob Carver started up his own company
called Sunfire after selling "Carver" to some investment firm.

Good luck with it, you found a real challenge there.

-bruce
[email protected]

 

[Mark D. Zacharias]

[email protected] wrote:
: bytraper:

: The good news is that because a stereo amplifier has duplicate
: circuitry in the Left and Right channels you can easily make circuitry
: comparisons. It would be unusual that BOTH channels would have
: exactly the same failures so be certain to look at the things that both
: channels have in common like the power supply and the switch positions,

The bad news is the Carver stuff from that era didn't use conventional
designs and the above would probably not apply.

Most of his amps were rated from 350 to 600 watts rms but the heaviest of
them was probably around only 20 pounds. The power supplies in those were
very unusual (named magnetic field) compared to standard amps and likely
the
problem with the amp is related to that.

Although hunt and peck might work, this is really one peice of hardware
one
should have the manual on, at least the schematic to examine the power
supply portion of it. The "grounds" on those amps should be particularly
noted. It's not a hot chassis like modern day tv's are but the rail
voltages (from memory) aren't taken from what you think is ground. More of
a
reference voltage from that triac thing to other points.

Anyway, scout around ebay, there is usually a guy on there selling the
manuals for those things. Probably photocopies but should be under $10.

Note that these amps had dozen of circuit mods made to them at the factory
and chances are none of the "factory" schematics show them. Also I haven't
checked recently but parts for the exotic stuff were next to impossible to
get even just 5-6 years ago. Think Bob Carver started up his own company
called Sunfire after selling "Carver" to some investment firm.

Good luck with it, you found a real challenge there.

-bruce
[email protected]

I would just recommend getting a specialist to repair it. Carvers are pretty
"special". I have seen bad solder at an input coupling cap on one of these,
though.

Mark Z.