Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

This can be the main filter capacitors, and or also a regulation problem in
the power supply. I have seen faults in the output stage also cause hum and
noise.

If you are not experienced at servicing these amplifiers, your best solution
would be to give it out to someone who is experienced at servicing this type
of amplifier. It is also a fairly high end unit, and is worth investing in a
proper repair. At home you may not have the proper test gear to verify its
operation after parts have been changed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Tom Noll" wrote in message
om...
Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

This can be the main filter capacitors, and or also a regulation problem in
the power supply. I have seen faults in the output stage also cause hum and
noise.

If you are not experienced at servicing these amplifiers, your best solution
would be to give it out to someone who is experienced at servicing this type
of amplifier. It is also a fairly high end unit, and is worth investing in a
proper repair. At home you may not have the proper test gear to verify its
operation after parts have been changed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Tom Noll" wrote in message
om...
Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

This can be the main filter capacitors, and or also a regulation problem in
the power supply. I have seen faults in the output stage also cause hum and
noise.

If you are not experienced at servicing these amplifiers, your best solution
would be to give it out to someone who is experienced at servicing this type
of amplifier. It is also a fairly high end unit, and is worth investing in a
proper repair. At home you may not have the proper test gear to verify its
operation after parts have been changed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Tom Noll" wrote in message
om...
Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

This can be the main filter capacitors, and or also a regulation problem in
the power supply. I have seen faults in the output stage also cause hum and
noise.

If you are not experienced at servicing these amplifiers, your best solution
would be to give it out to someone who is experienced at servicing this type
of amplifier. It is also a fairly high end unit, and is worth investing in a
proper repair. At home you may not have the proper test gear to verify its
operation after parts have been changed.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Tom Noll" wrote in message
om...
Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

Sounds like the doubler caps are bad, B+ will probably be low,
especially under load.

Terry
www.mcintoshaudio.com

On 6 May 2004 06:47:13 -0700, (Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

Terry
WB4NHB
www.mcintoshaudio.com

Sounds like the doubler caps are bad, B+ will probably be low,
especially under load.

Terry
www.mcintoshaudio.com

On 6 May 2004 06:47:13 -0700, (Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

Terry
WB4NHB
www.mcintoshaudio.com

Sounds like the doubler caps are bad, B+ will probably be low,
especially under load.

Terry
www.mcintoshaudio.com

On 6 May 2004 06:47:13 -0700, (Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

Terry
WB4NHB
www.mcintoshaudio.com

Sounds like the doubler caps are bad, B+ will probably be low,
especially under load.

Terry
www.mcintoshaudio.com

On 6 May 2004 06:47:13 -0700, (Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.

Best regards,

Tom

Terry
WB4NHB
www.mcintoshaudio.com

(Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.


If the hum comes only from the chassis, and is not present on the
speaker's sound, then it may be a mechanic problem. Check for lossen
screws on the power transformer mounting.
Best regards,

Tom

---
Ing. Remberto Gomez-Meda
http://ingemeda.tripod.com/
INGE - Ingenieria Electronica.
Puerto Vallarta, Jalisco, Mexico.

(Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.


If the hum comes only from the chassis, and is not present on the
speaker's sound, then it may be a mechanic problem. Check for lossen
screws on the power transformer mounting.
Best regards,

Tom

---
Ing. Remberto Gomez-Meda
http://ingemeda.tripod.com/
INGE - Ingenieria Electronica.
Puerto Vallarta, Jalisco, Mexico.

(Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.


If the hum comes only from the chassis, and is not present on the
speaker's sound, then it may be a mechanic problem. Check for lossen
screws on the power transformer mounting.
Best regards,

Tom

---
Ing. Remberto Gomez-Meda
http://ingemeda.tripod.com/
INGE - Ingenieria Electronica.
Puerto Vallarta, Jalisco, Mexico.

(Tom Noll) wrote:

Hello,

Last night when I turned off the stereo I noticed a new noise. As I
went over to pull the switch, I noticed an obvious hum, which sounds
like 60Hz, coming from the chassis of the MC-240. There is also seems
to be some vibration present. I believe that there is no change in the
sound as presented as signal to the speakers; no hum or excess noise.
This is the sort of sound that comes from an overloaded transformer--
but the power transformer was not overly warm, I think. My setup
involves no preamp, just a CD run straight into the amp. All
connections look unchanged and good.

Today I'll check the voltages out. I have no technical experience with
this amp, but know my way around with a DVM.

Is this hum a sign of some particular problem? Is there some
particular component or measurement I should look into?

Thanks for any help or suggestions.


If the hum comes only from the chassis, and is not present on the
speaker's sound, then it may be a mechanic problem. Check for lossen
screws on the power transformer mounting.
Best regards,

Tom

---
Ing. Remberto Gomez-Meda
http://ingemeda.tripod.com/
INGE - Ingenieria Electronica.
Puerto Vallarta, Jalisco, Mexico.

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Tom,

The parts list from McIntosh does list the caps as 250 Volt, and you
should replace both of them, as they are in a series voltage doubler
arrangement and the caps must be identical. The capacitor with the
black cardboard sleeve has lots of voltage on the can itself, which is
why the can is also insulated from the chassis. You can go a bit higher
in capacitance (up to around 330uf) and higher voltage ratings are OK.
It might be difficult to find these caps, you might want to try someone
like Antique Electronics Supply (www.tubesandmore.com). Remember there
are hazardous voltages inside this amp, and misconnection of these caps
is dangerous. Best of luck.

Regards,
Tim Schwartz
Bristol Electronics


Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Tom,

The parts list from McIntosh does list the caps as 250 Volt, and you
should replace both of them, as they are in a series voltage doubler
arrangement and the caps must be identical. The capacitor with the
black cardboard sleeve has lots of voltage on the can itself, which is
why the can is also insulated from the chassis. You can go a bit higher
in capacitance (up to around 330uf) and higher voltage ratings are OK.
It might be difficult to find these caps, you might want to try someone
like Antique Electronics Supply (www.tubesandmore.com). Remember there
are hazardous voltages inside this amp, and misconnection of these caps
is dangerous. Best of luck.

Regards,
Tim Schwartz
Bristol Electronics


Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Tom,

The parts list from McIntosh does list the caps as 250 Volt, and you
should replace both of them, as they are in a series voltage doubler
arrangement and the caps must be identical. The capacitor with the
black cardboard sleeve has lots of voltage on the can itself, which is
why the can is also insulated from the chassis. You can go a bit higher
in capacitance (up to around 330uf) and higher voltage ratings are OK.
It might be difficult to find these caps, you might want to try someone
like Antique Electronics Supply (www.tubesandmore.com). Remember there
are hazardous voltages inside this amp, and misconnection of these caps
is dangerous. Best of luck.

Regards,
Tim Schwartz
Bristol Electronics


Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Tom,

The parts list from McIntosh does list the caps as 250 Volt, and you
should replace both of them, as they are in a series voltage doubler
arrangement and the caps must be identical. The capacitor with the
black cardboard sleeve has lots of voltage on the can itself, which is
why the can is also insulated from the chassis. You can go a bit higher
in capacitance (up to around 330uf) and higher voltage ratings are OK.
It might be difficult to find these caps, you might want to try someone
like Antique Electronics Supply (www.tubesandmore.com). Remember there
are hazardous voltages inside this amp, and misconnection of these caps
is dangerous. Best of luck.

Regards,
Tim Schwartz
Bristol Electronics


Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Thanks again, and with best regards,

Tom

Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Some time ago a student built his own McIntosh style amp as a thesis
project. I've long forgotten the guy's name, but the upshot was that
distortion seemed a little high and it turned out one tube had turned
out to have almost zero emission.

Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Some time ago a student built his own McIntosh style amp as a thesis
project. I've long forgotten the guy's name, but the upshot was that
distortion seemed a little high and it turned out one tube had turned
out to have almost zero emission.

Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Some time ago a student built his own McIntosh style amp as a thesis
project. I've long forgotten the guy's name, but the upshot was that
distortion seemed a little high and it turned out one tube had turned
out to have almost zero emission.

Tom Noll wrote:

Thanks for your help, guys. The first filter cap had leaked and all
the high voltages are much too low, so the doubler caps are bad too.

Next question: what voltage rating do I need to replace that doubler
cap which floats and is wrapped in black cardboard? For both caps the
schematic calls for 250 mF no voltage rating given, the bare can is a
250 V unit. I've noticed that schematic values are not always
reliable.

The other question is how could that amplifier have sounded so good
when it was so out of whack? Ans: the Macintosh engineering for fault
tolerance is well-earned.

Some time ago a student built his own McIntosh style amp as a thesis
project. I've long forgotten the guy's name, but the upshot was that
distortion seemed a little high and it turned out one tube had turned
out to have almost zero emission.