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Harmon Kardon A401
Harmon Kardon A401
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Old Yesterday, 03:55 PM   #1
mr2racer is offline mr2racer  United States
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Default Harmon Kardon A401

Hello Everyone.

I have a Harmon Kardon A401 integrated amplifier. I bought it new in 1976. Later I sold it to a friend who returned as junk a few years ago. I replaced all the electrolytics and the output transistors. It works again and sounds alright. My question is if I replace the small signal transistors with up to date versions will it sound better? Or is it a waste of time and money? I've attached a list of those transistors. Most are no longer available so I would have to find substitutes.

Thanks, Kevin
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File Type: jpg A401 Small Signal.jpg (33.9 KB, 35 views)
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Last edited by mr2racer; Yesterday at 04:00 PM.
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Old Yesterday, 04:00 PM   #2
nigelwright7557 is offline nigelwright7557  United Kingdom
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I would never replace semiconductors in an amp unless they are definitely faulty.

Putting in faster transistors can result in oscillation and/or instability.
So I would just leave them be.

Electrolytics are the things that age fastest so replacing those was the right way to go.
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Old Yesterday, 04:49 PM   #3
mr2racer is offline mr2racer  United States
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Thanks Nigel. I'm a tube guy so I know little about transistors. Some of the electrolytics seemed to be glued to the boards. I guess that was the electrolytic leaking out of them?
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Old Yesterday, 06:39 PM   #4
Ylli is offline Ylli  United States
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Most of the time the 'glue' is there to mechanically stabilize the part. Electrolytic capacitors tend to be a bit massive, and gluing them to the board helps prevent mechanical stress failure of the leads. But leakage is certainly possible.
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Old Yesterday, 06:44 PM   #5
Mooly is offline Mooly  United Kingdom
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Harmon Kardon A401
Changing the transistors won't change the sound quality at all... and as Nigel hints at, if you make a wrong choice it could bring new issues to the table.
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Old Yesterday, 07:02 PM   #6
huggygood is offline huggygood  France
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