Carver M500t Electrical buzzing after warm up

[DManzaluni]

I have a reasonably loud Electrical buzzing about 10 minutes after
warm up on my Carver M500t which I suppose is a bit elderly by now.

Sorry if this sounds a bit unsepcific but does anyone know what can
cause that type of thing please? Do these things suffer from anything
as simple as leaky caps or is the unit probably terminal.

(I should add that I am in New York where there is unlikely to be
anyone nearby who can fix it so if it is not easy, I amy well not be
able to do it myself)

 

[DManzaluni]

Perhaps the power transformer. Not too uncommon. No good fix I know of
though...

Mark Z.

Thanks Mark, unless anyone out there has any other ideas, that was the
answer I was NOT trying desperately to avoid. It is what I was
suspecting myself and I wanted someone to tell me I was wrong. It
does sound like a combination of transformer hum (coming thorugh the
speakers) and something worse.

Curiously enough there are a few out there at the moment being sold
off inexpensively but they sound like power transformers too!
(continuously blown fuses)

 

[Dave]

I have a reasonably loud Electrical buzzing about 10 minutes after
warm up on my Carver M500t which I suppose is a bit elderly by now.

Sorry if this sounds a bit unsepcific but does anyone know what can
cause that type of thing please? Do these things suffer from anything
as simple as leaky caps or is the unit probably terminal.

(I should add that I am in New York where there is unlikely to be
anyone nearby who can fix it so if it is not easy, I amy well not be
able to do it myself)

The electrical buzzing, does it come through the loudspeakers or is it more
of a mechanical vibration emanating from the amp/transformer itself? If
it's coming through the speakers, I'd look at replacing the (either 2 or 4)
large electrolytic power supply filter caps... they definitely DO have a
finite lifespan. The power transformer should work forever unless it's
asked to provide more current than it is able. Even then there should be a
thermal fuse in the windings which would keep the windings from shorting.

Often the most difficult part of this re-cap is sourcing caps which are the
proper size and rating. If you have trouble sourcing try posting on
AudioKarma or AudioAsylum boards, those guys have a lot of experience with
this type of repair.

Dave

 

[DManzaluni]

The electrical buzzing, does it come through the loudspeakers or is it more
of a mechanical vibration emanating from the amp/transformer itself?  If
it's coming through the speakers, I'd look at replacing the (either 2 or 4)
large electrolytic power supply filter caps... they definitely DO have a
finite lifespan.  The power transformer should work forever unless it's
asked to provide more current than it is able.  Even then there should be a
thermal fuse in the windings which would keep the windings from shorting.

Often the most difficult part of this re-cap is sourcing caps which are the
proper size and rating.  If you have trouble sourcing try posting on
AudioKarma or AudioAsylum boards, those guys have a lot of experience with
this type of repair.

Dave

Well that sounds more hopeful: I thought I had said that the sound
does come from the speakers: Apparently not! I might even be able to
do it myself if it is just filter caps: They tend to be relatively
separate from the rest of the internals. Is it this way in the Carver?
And how do I ascertain what the values are? I am in New York where
getting unusual caps shouldn't be too impossible.

 

[Bruce Esquibel]

Well that sounds more hopeful: I thought I had said that the sound
does come from the speakers: Apparently not! I might even be able to
do it myself if it is just filter caps: They tend to be relatively
separate from the rest of the internals. Is it this way in the Carver?
And how do I ascertain what the values are? I am in New York where
getting unusual caps shouldn't be too impossible.

I think I have bad news for you.

Unless that model was out of the series Carver made in the 1980's, it doesn't
follow standard amplifier designs.

He (Bob Carver) used something he called "Magnetic Field" something or other
and the power supply in there isn't like anything you can think of.

Basically they produced amps like the 1.5t where it could output 1200 watts
RMS (short term, like 4 or 6 seconds) per channel in a box that weighs
around 15 pounds.

The key was the power supply, it used some kind of "loose wound" core and
a special triac tied into it somehow that controlled regulation.

Although the caps probably can be found somewhere, I think the problem is
the transformer itself. They made buzzing noises in all the models and I
beleive it's from whatever they used to gunk the "loose core" inside of it.

I'm saying it's more mechanical than electronic.

I think at this point in time you may only have the choice of finding another
M500t which has some other problem and scavenge the transformer out of it.

If Carver is still around it's like so many other companies where it's name
lives on but has nothing to do with what it made in the past.

Bob Carver is behind another company called Sunfire but I really don't know
if they can or will handle problems with the old Carver stuff. I think
this was one of those messy situations where he signed over the patents and
technology to the "new Carver" which went into the toilet.

A bit of history with that letter t after the model name, it stands for
"transfer function". In the 80's Bob Carver claimed that he could listen to
any audio amp and copy the sound characteristics into his amp design making
a clone of it.

One audio magazine (Stereophile) took up the challenge and brought him in
to listen to some high end, mega dollar amplifier. He listened and tweaked,
listened and tweaked more, ending up with a virtual clone of the mega
dollar amp. Although the challenge was debated for years, it does seem he
accomplished his claim.

Thus all his amps ending with that letter t is supposed to have the same
sonic quality (however you want to descibe that) of that mega dollar amp
from the challenge.

-bruce
[email protected]

 

[DManzaluni]

I think I have bad news for you.

Unless that model was out of the series Carver made in the 1980's, it doesn't
follow standard amplifier designs.

He (Bob Carver) used something he called "Magnetic Field" something or other
and the power supply in there isn't like anything you can think of.

Basically they produced amps like the 1.5t where it could output 1200 watts
RMS (short term, like 4 or 6 seconds) per channel in a box that weighs
around 15 pounds.

The key was the power supply, it used some kind of "loose wound" core and
a special triac tied into it somehow that controlled regulation.

Although the caps probably can be found somewhere, I think the problem is
the transformer itself. They made buzzing noises in all the models and I
beleive it's from whatever they used to gunk the "loose core" inside of it.

I'm saying it's more mechanical than electronic.

I think at this point in time you may only have the choice of finding another
M500t which has some other problem and scavenge the transformer out of it..

If Carver is still around it's like so many other companies where it's name
lives on but has nothing to do with what it made in the past.

Bob Carver is behind another company called Sunfire but I really don't know
if they can or will handle problems with the old Carver stuff. I think
this was one of those messy situations where he signed over the patents and
technology to the "new Carver" which went into the toilet.

A bit of history with that letter t after the model name, it stands for
"transfer function". In the 80's Bob Carver claimed that he could listen to
any audio amp and copy the sound characteristics into his amp design making
a clone of it.

One audio magazine (Stereophile) took up the challenge and brought him in
to listen to some high end, mega dollar amplifier. He listened and tweaked,
listened and tweaked more, ending up with a virtual clone of the mega
dollar amp. Although the challenge was debated for years, it does seem he
accomplished his claim.

Thus all his amps ending with that letter t is supposed to have the same
sonic quality (however you want to descibe that) of that mega dollar amp
from the challenge.

-bruce
[email protected]

But this isnt a mechanical sound coming from the transformer, it is an
electronic sound coming from the speakers

 

[Bruce Esquibel]

But this isnt a mechanical sound coming from the transformer, it is an
electronic sound coming from the speakers

Sorry, when I saw this from the last post you made...

Well that sounds more hopeful: I thought I had said that the sound
does come from the speakers: Apparently not! I might even be able to

I took that to mean it wasn't coming from the speakers but the unit itself.

In that case by all means try replacing all the large style electrolytics
in there. They used to be standard but these days who knows.

-bruce
[email protected]

 

[Gareth Magennis]

I think I have bad news for you.

Unless that model was out of the series Carver made in the 1980's, it
doesn't
follow standard amplifier designs.

He (Bob Carver) used something he called "Magnetic Field" something or
other
and the power supply in there isn't like anything you can think of.

Basically they produced amps like the 1.5t where it could output 1200
watts
RMS (short term, like 4 or 6 seconds) per channel in a box that weighs
around 15 pounds.

The key was the power supply, it used some kind of "loose wound" core and
a special triac tied into it somehow that controlled regulation.

Although the caps probably can be found somewhere, I think the problem is
the transformer itself. They made buzzing noises in all the models and I
beleive it's from whatever they used to gunk the "loose core" inside of
it.

I'm saying it's more mechanical than electronic.

I think at this point in time you may only have the choice of finding
another
M500t which has some other problem and scavenge the transformer out of it.

If Carver is still around it's like so many other companies where it's
name
lives on but has nothing to do with what it made in the past.

Bob Carver is behind another company called Sunfire but I really don't
know
if they can or will handle problems with the old Carver stuff. I think
this was one of those messy situations where he signed over the patents
and
technology to the "new Carver" which went into the toilet.

A bit of history with that letter t after the model name, it stands for
"transfer function". In the 80's Bob Carver claimed that he could listen
to
any audio amp and copy the sound characteristics into his amp design
making
a clone of it.

One audio magazine (Stereophile) took up the challenge and brought him in
to listen to some high end, mega dollar amplifier. He listened and
tweaked,
listened and tweaked more, ending up with a virtual clone of the mega
dollar amp. Although the challenge was debated for years, it does seem he
accomplished his claim.

Thus all his amps ending with that letter t is supposed to have the same
sonic quality (however you want to descibe that) of that mega dollar amp
from the challenge.

-bruce
[email protected]

But this isnt a mechanical sound coming from the transformer, it is an
electronic sound coming from the speakers



I've had some experience, years ago, with the Carver PM1.5 type amps. They
had a switched power supply via a triac. They also had a voltage adjustment
preset. If the power supply voltage was too low you could get constant
switching noise from the amps output. Correcting the voltage eliminated the
noise.

IIRC the voltages were around + and - 120v, perhaps a bit less - you might
want to check the caps' voltage rating and take adequate precautions!

(The PM1.5 used a dual power supply - the 120v supply was switched in to
drive additional output transistors when the signal exceeded that of the
lower voltage supply. This gave quite good headroom)


Gareth.