home 5-channel amplifier problem

P

Pentti J. Kantanen

Guest
Hello, I'm in need of some hints here..
I have a regular four channel kenwood amplifier/radio unit that one day
started to make crackling and bussing sounds at all outputs..
Inside I found a blown electrolytic capacitor (the insides had been
pushed out through a small hole that had appeared on top of the cap).
It seems the cap is in the power supply quite near a reulator, maybe
filtering the 50Hz AC out or something?
Anyways, I contacted Elna (the manufacturer of the cap) and sent them
the part, they were nice enough to send me an exact replacement.

I replaced the part on the board and found that the amplifier does not
work anymore.. It powers one but the display is messed up and nothing
works. Looks like over/under voltage from the power supply to me.
I measured something like 35V DC from the cap, slightly more than the
rating. I can't see any other visible damage or oddities.
The blown cap does stand very close to a heatsink that I believe is the
regulator's.

Maybe the cap was blown because of over voltage in the unit? How come
the unit worked with the blown cap but not with a good one? What causes
this overvoltage?
Any repair hints or things to measure?
 
My thoughts:

Did you get the polarity on the new capacitor correct? Did you disturb or
need to remove any other components/connectors/etc. when you removed the
defective capacitor? Was the circuit board contaminated by the exploding
electrolyte? Was the new part soldered in correctly without introducing any
new shorts/faults? Is there a defective regulator, diode, or other active
component in the supply circuit?

Good luck

Bob

"Pentti J. Kantanen" <guess.what@dnainternet.net> wrote in message
news:4092a674$1_1@news.dnainternet.net...
Hello, I'm in need of some hints here..
I have a regular four channel kenwood amplifier/radio unit that one day
started to make crackling and bussing sounds at all outputs..
Inside I found a blown electrolytic capacitor (the insides had been
pushed out through a small hole that had appeared on top of the cap).
It seems the cap is in the power supply quite near a reulator, maybe
filtering the 50Hz AC out or something?
Anyways, I contacted Elna (the manufacturer of the cap) and sent them
the part, they were nice enough to send me an exact replacement.

I replaced the part on the board and found that the amplifier does not
work anymore.. It powers one but the display is messed up and nothing
works. Looks like over/under voltage from the power supply to me.
I measured something like 35V DC from the cap, slightly more than the
rating. I can't see any other visible damage or oddities.
The blown cap does stand very close to a heatsink that I believe is the
regulator's.

Maybe the cap was blown because of over voltage in the unit? How come
the unit worked with the blown cap but not with a good one? What causes
this overvoltage?
Any repair hints or things to measure?
Click to expand...
 
To be honest I did try a bit different cap in there firs. It was of the
same uF rating but a higher voltage one, electrolytic also.

I didn't touch any other components and the blown cap leaked only on
itself, no damage on the board or other components.

I most definitely installed both parts the right way around. + and minus
signs were printed on the board.

The cap seems to be right where the power comes into the bigger
mainboard from the transformer/rectifier board, before the regulator.

It was an easy job to replace the cap, I don't think I broke anything.

Bob Shuman wrote:
My thoughts:

Did you get the polarity on the new capacitor correct? Did you disturb or
need to remove any other components/connectors/etc. when you removed the
defective capacitor? Was the circuit board contaminated by the exploding
electrolyte? Was the new part soldered in correctly without introducing any
new shorts/faults? Is there a defective regulator, diode, or other active
component in the supply circuit?

Good luck

Bob

"Pentti J. Kantanen" <guess.what@dnainternet.net> wrote in message
news:4092a674$1_1@news.dnainternet.net...

Hello, I'm in need of some hints here..
I have a regular four channel kenwood amplifier/radio unit that one day
started to make crackling and bussing sounds at all outputs..
Inside I found a blown electrolytic capacitor (the insides had been
pushed out through a small hole that had appeared on top of the cap).
It seems the cap is in the power supply quite near a reulator, maybe
filtering the 50Hz AC out or something?
Anyways, I contacted Elna (the manufacturer of the cap) and sent them
the part, they were nice enough to send me an exact replacement.

I replaced the part on the board and found that the amplifier does not
work anymore.. It powers one but the display is messed up and nothing
works. Looks like over/under voltage from the power supply to me.
I measured something like 35V DC from the cap, slightly more than the
rating. I can't see any other visible damage or oddities.
The blown cap does stand very close to a heatsink that I believe is the
regulator's.

Maybe the cap was blown because of over voltage in the unit? How come
the unit worked with the blown cap but not with a good one? What causes
this overvoltage?
Any repair hints or things to measure?
Click to expand...
 
Installing cap with same capacitance and higher voltage rating won't do any
bad to functionality or performance.

"Pentti J. Kantanen" <guess.what@dnainternet.net> wrote in message
news:4092bb85$1_1@news.dnainternet.net...
To be honest I did try a bit different cap in there firs. It was of the
same uF rating but a higher voltage one, electrolytic also.

I didn't touch any other components and the blown cap leaked only on
itself, no damage on the board or other components.

I most definitely installed both parts the right way around. + and minus
signs were printed on the board.

The cap seems to be right where the power comes into the bigger
mainboard from the transformer/rectifier board, before the regulator.

It was an easy job to replace the cap, I don't think I broke anything.

Bob Shuman wrote:
My thoughts:

Did you get the polarity on the new capacitor correct? Did you disturb
or
need to remove any other components/connectors/etc. when you removed the
defective capacitor? Was the circuit board contaminated by the
exploding
electrolyte? Was the new part soldered in correctly without introducing
any
new shorts/faults? Is there a defective regulator, diode, or other
active
component in the supply circuit?

Good luck

Bob

"Pentti J. Kantanen" <guess.what@dnainternet.net> wrote in message
news:4092a674$1_1@news.dnainternet.net...

Hello, I'm in need of some hints here..
I have a regular four channel kenwood amplifier/radio unit that one day
started to make crackling and bussing sounds at all outputs..
Inside I found a blown electrolytic capacitor (the insides had been
pushed out through a small hole that had appeared on top of the cap).
It seems the cap is in the power supply quite near a reulator, maybe
filtering the 50Hz AC out or something?
Anyways, I contacted Elna (the manufacturer of the cap) and sent them
the part, they were nice enough to send me an exact replacement.

I replaced the part on the board and found that the amplifier does not
work anymore.. It powers one but the display is messed up and nothing
works. Looks like over/under voltage from the power supply to me.
I measured something like 35V DC from the cap, slightly more than the
rating. I can't see any other visible damage or oddities.
The blown cap does stand very close to a heatsink that I believe is the
regulator's.

Maybe the cap was blown because of over voltage in the unit? How come
the unit worked with the blown cap but not with a good one? What causes
this overvoltage?
Any repair hints or things to measure?
Click to expand...
 
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