[[email protected]]

Hello.

I have a pretty old receiver, Marantz MR250, more than 20 yrs old
actually. Its sound is still wonderful. Only problem is - occasionally
it gives this "boom" sound from the speakers. The exploding sound is
indepentent of the volume, how hot the receiver is, or anything else.

I think it may have something to do with old capacitors.

Anyone knows what's the problem?

thanx,

at44...

[harrogate3]

wrote in message
ups.com...
Hello.

I have a pretty old receiver, Marantz MR250, more than 20 yrs old
actually. Its sound is still wonderful. Only problem is -
occasionally
it gives this "boom" sound from the speakers. The exploding sound is
indepentent of the volume, how hot the receiver is, or anything
else.

I think it may have something to do with old capacitors.

Anyone knows what's the problem?

thanx,

at44...



Older amps often have a single supply rail requiring a large isolating
capacitor in series with the loudspeaker. This capacitor has to charge
up when the amp is first switched on and produces the characteristic
audible 'thump' from the loudspeakers.

Could it be that you have a faulty supply connection within the amp
that means that there is sufficient capacitance on the amp rails to
keep it going for a while but that will allow the output cap to run
down and need to recharge?


--
Woody

harrogate3 at ntlworld dot com

[Mark D. Zacharias]

harrogate3 wrote:
wrote in message
ups.com...
Hello.

I have a pretty old receiver, Marantz MR250, more than 20 yrs old
actually. Its sound is still wonderful. Only problem is -
occasionally it gives this "boom" sound from the speakers. The
exploding sound is indepentent of the volume, how hot the receiver
is, or anything else.

I think it may have something to do with old capacitors.

Anyone knows what's the problem?

thanx,

at44...



Older amps often have a single supply rail requiring a large isolating
capacitor in series with the loudspeaker. This capacitor has to charge
up when the amp is first switched on and produces the characteristic
audible 'thump' from the loudspeakers.

Could it be that you have a faulty supply connection within the amp
that means that there is sufficient capacitance on the amp rails to
keep it going for a while but that will allow the output cap to run
down and need to recharge?

Why assume that this model has only a single-ended power supply? It was
marketed years after Marantz went to split supplies and direct-coupled
outputs.

Regarding the OP's question, we here on Usenet cannot hear your symptom, and
so at this point are just guessing, like the other reply was guessing.

If your sound is in the nature of a loud "POP" then that is a sudden DC
shift. In your case may be caused by a bad solder connection or maybe a bad
voltage amp IC - Marantz and others had some problems with those in the time
frame from which your receiver came.


Mark Z.

[Paul Guy]

On 7 Aug 2006 15:59:06 -0700, wrote:

Hello.

I have a pretty old receiver, Marantz MR250, more than 20 yrs old
actually. Its sound is still wonderful. Only problem is - occasionally
it gives this "boom" sound from the speakers. The exploding sound is
indepentent of the volume, how hot the receiver is, or anything else.

I think it may have something to do with old capacitors.

Anyone knows what's the problem?

thanx,

at44...


I have a Marantz 2245 that had similiar problems. In my case only
ONE channel had the problem, it was independent of volume control,
tape loop, etc. I pulled out the power amp "module" (heatsink+plus
board) for the offending channel, and discovered there were only a few
electrolytic capacitors... 20 uF at 25 volts if I remember. So I
replaced all of them. Problem went away!
The amplifier sections aren't very pleasant to service... draw
pictures of wire connections, and take care with your
soldering/desoldering. With typical equipment, it will take you 2-3
hours, if you are very careful.
You didn't say if BOTH channels are affected. If so, then the above
solution won't work for you.
The capacitors aren't very expensive.... should be a buck or less
each. Watch out for polarity when you remove them (it should be shown
on the board, or remember what polarity position the old ones had). If
you screw up polarity, chances are you may cause real performance
problems, or the amp could overheat and burn itself out.

Paul
.................................................. .............
Paul
Somewhere in a Nova Scotian fog
ANTISPAM - Please remove the m's in my email address

[Mark D. Zacharias]

Paul Guy wrote:
On 7 Aug 2006 15:59:06 -0700, wrote:

Hello.

I have a pretty old receiver, Marantz MR250, more than 20 yrs old
actually. Its sound is still wonderful. Only problem is -
occasionally it gives this "boom" sound from the speakers. The
exploding sound is indepentent of the volume, how hot the receiver
is, or anything else.

I think it may have something to do with old capacitors.

Anyone knows what's the problem?

thanx,

at44...


I have a Marantz 2245 that had similiar problems. In my case only
ONE channel had the problem, it was independent of volume control,
tape loop, etc. I pulled out the power amp "module" (heatsink+plus
board) for the offending channel, and discovered there were only a few
electrolytic capacitors... 20 uF at 25 volts if I remember. So I
replaced all of them. Problem went away!
The amplifier sections aren't very pleasant to service... draw
pictures of wire connections, and take care with your
soldering/desoldering. With typical equipment, it will take you 2-3
hours, if you are very careful.
You didn't say if BOTH channels are affected. If so, then the above
solution won't work for you.
The capacitors aren't very expensive.... should be a buck or less
each. Watch out for polarity when you remove them (it should be shown
on the board, or remember what polarity position the old ones had). If
you screw up polarity, chances are you may cause real performance
problems, or the amp could overheat and burn itself out.

Paul
.................................................. ............
Paul
Somewhere in a Nova Scotian fog
ANTISPAM - Please remove the m's in my email address


The 2245 is toally different than the OP's MR-250. Not even made in the same
factory or by the same company, really.

Pretty good generic advice for amp servicing, though...

Mark Z.