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Harman Kardon PM655

Ultra Wideband Integrated Amplifier (1985-86)

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Harman Kardon PM655


Power output: 60 watts per channel into 8Ω (stereo)

Frequency response: 0.2Hz to 150kHz

Total harmonic distortion: 0.08%

Damping factor: 65

Input sensitivity: 0.12mV (MC), 2.2mV (MM), 135mV (line)

Signal to noise ratio: 77dB (MC), 79dB (MM), 80dB (line)

Dimensions: 443 x 134 x 398mm

Weight: 10.3kg


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PM655 in repair... No Bass, all other OK

Hello everybody.

First sorry but my english is not good. I get a amplifier from my friend to repair. I haven´t too much experience with a amplifiers and I don´t found the problem. I searching some hours ago why zero bass coming out.

The amplifier is working, power amp, pre amp, treble control, balance are OK. Only if I turned the potmeter for BASS, nothing happened. I resoldered many many old and broken contact because thats a very old machine :).

I downloaded both schematics and checked. I checked the "Bass Control Circuit" and Q901, Q903, Q905 looks like OK and every voltage is arround the nominal. I don´t found where I have a chance to found the error.

I haven´t more idea where is the best to search. Maybe somebody have some idea for me. If yes, please comment here.

Thank you very very much.

Erfurt, Germany.

no bass

check electrolitic caps in signalpath, sometimes they loose capacity.
Regards Werner

capacitors - signalpath

No results. Looks like all is fine. Only 4 dead capacitors on the phono preamp. 4x330uF 25V. But after I installed a new ones, everything same (of course). Or maybe I don´t see the important capacitor. But I think I checked all what is in the signalpath. And mostly all capacitor had a very very good capacity. And not with 20-30% different like the new cheap capacitors... 47uF is 47uF, 1uF is 1uF. My all new capacitors is more bad. Not like this 30 years old ones :)

Harman Kardon PM 655vxi Bias too high after repair

If the output transistors 2SC3281, 2SA1302 are changed to the today commonly available ISC types bias adjustment range may be too low. Simplest cure is to increase R456 (or R457 of the other channel) to 1k .. 1k2.

This website is not affiliated with or sponsored by Harman Kardon. To purchase PM655 spares or accessories, please contact the company via their website or visit an authorised retailer.