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How to Revive an Aging Amp
How to Revive an Aging Amp
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Old 30th June 2004, 06:17 AM   #1
caesar148 is offline caesar148  United States
diyAudio Member
Join Date: May 2004
Location: S. California
Default How to Revive an Aging Amp

I have a Parasound HCA-220II power amp which is showing its age. The midrange and bass isn't dynamic and fast as it used to be. Also, there seem to be a lost of details. I am wondering what I can do to bring the life back to this amp. I am thinking of several options:

1) Replace the bulk caps to newer and bigger caps. Originally values are 25,000 uF. What value should I use?

2) Replace the retifier diodes to higher current type.

3) Replace all the power transistors to new ones. There are 2SC3263 and 2SA1294. A total of 24 pieces altogether Not sure if this helps.

Will these modification work and are thre anything else I can do to improve the sournd?
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Old 30th June 2004, 04:08 PM   #2
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK
I suggest replacing all the electrolytics only.

Better quality types are available, you can increase values by
a notch, e.g. 25->33, 33->47, 47->63 etc, double the smaller
values if you are so inclined, in a power amplifier should be fine.

For the electrolytics in the signal chain there is some mileage in
increasing voltage ratings, and bypassing with polycarbonate
types (or more expensive and larger polypropylene).

Clean all input and output sockets.

Finally with a soldering iron, solder and solder pump, methodically
resolder every joint in the amplifier. If your iron is not big enough
leave the larger joints for the power supply lines etc.

Replacing semiconductors will not help IMO.

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Old 1st July 2004, 07:22 PM   #3
lucpes is offline lucpes  Romania
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Join Date: Dec 2003
Location: Romania, EU
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Most likely the big electrolytics are ok so I'd leave them like that.

Support changing all the other electrolytics, Panasonic FC is very good & cheap for this purpose.

To properly solder the power lines (soldering is better with time instead of using crimped stuff in power amps or speakers) use a 100W soldering iron or get a soldering gun for this stuff only. Check fuse holders for oxidized parts. Clean all connectors with a contact cleaner.

Also check the connections for the speaker cable for loose/oxidized issues.

Regarding output trannies, there's no such thing as transistor aging.
We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines. Measurements can provide a measure of insight, but are no substitute for human judgment. Nelson Pass
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