Help with Harman Kardon PM 655 Vxi phono input?

[Babyboomer78]

I am the original owner of a HK PM 655 Vxi. Love the amp. Recently no output at all from the phono input (I only use MM) I was using compressed air and gave a shot to the stylus; I think the amp was powered on but speakers were off, and the problem seems to have happened near that time, but I'm not certain. Did I blow a preamp fuse (is there one?) or worse? CD player still sounds fine through the amp, and turntable checks out fine on a different amp. Thoughts? I am handy but not a technician, able to remove cover and maybe do basic stuff....like fuses and deoxit, etc. Thanks and hope I can rescue this fine amp.

 

[chazix]

Did I blow a preamp fuse (is there one?)

Welcome to AK! I don't think I'll be able to help very much, but I can field this one: there are no fuses, as such, for the phono preamp.

There are phono-specific power supply regulators, and those regulators have certain parts that are known as fusible resistors. Those resistors would be soldered in place on a circuit board. It's conceivable that those resistors perished. (Actually, that kind of part is notorious for degrading just due to age, but it's unusual for them to fail so completely that they lead to a symptom like this one.)

There is also a muting circuit that's specific to phono, and I'm slightly inclined to think that's a more likely cause of the symptom. But I should admit that I don't understand how that muting function is supposed to work. The service manual I looked at is maddeningly obscured in some of the relevant parts of the schematic.

I'm afraid I think you're going to need a tech to diagnose and fix this.

BTW, are you sure that compressed air is a good way to clean a stylus? There will be other AKers who know more about that than me, but I can't see doing it, myself.

 

[WaynerN]

I have one of these amps as well. Did you check your MM/MC switch on the front panel? The button should be out for MM (moving magnet).

'ner

 

[Babyboomer78]

Thank you for the feedback. Yes, the MM switch is correct (I tried both!) . No, I don't think, in retrospect, I should use compressed air for this=too fragile. Not sure that caused the issue, but I will look for more gentle cleaning methods.
If you find anything else let me know - love this Harman Kardon amplifier!

 

[Akustic]

Have had a couple of HK's from that era ..
Nice gear with switches that occasionally fitz in and out ..

I got to the point that I would just flip all of the switches and knobs when there was a problem ..
So far that works for me .. Deoxit and try it again before digging in too far ..
The others are gone, but I still listen to a PM660 everyday .. it's a nice sounding amp.

 

[Akustic]

I am the original owner of a HK PM 655 Vxi. Love the amp. Recently no output at all from the phono input (I only use MM) I was using compressed air and gave a shot to the stylus; I think the amp was powered on but speakers were off, and the problem seems to have happened near that time, but I'm not certain. Did I blow a preamp fuse (is there one?) or worse? CD player still sounds fine through the amp, and turntable checks out fine on a different amp. Thoughts? I am handy but not a technician, able to remove cover and maybe do basic stuff....like fuses and deoxit, etc. Thanks and hope I can rescue this fine amp.

Harman's amps during the Matti Otala era were some very nice sounding amps .. clear, neutral & detailed but not sterile, hard or edgy .
They really were some of the best sounding and most powerful integrateds on the market .. They were first to market high current amps outside of the high end.
Not at all dark or syrupy like the Marantz's, Sansui's, or Pioneers of that era ..
If sound quality was on your shortlist, you were auditioning a Harman ..
They fell off during the 90's ..

 

[zebra03]

Have had a couple of HK's from that era ..
Nice gear with switches that occasionally fitz in and out ..

I got to the point that I would just flip all of the switches and knobs when there was a problem ..
So far that works for me .. Deoxit and try it again before digging in too far ..
The others are gone, but I still listen to a PM660 everyday .. it's a nice sounding amp.

Absolutely . Constant Deoxit sessions and knob twisting and button pushing seems to go hand and hand with this era of HK .

 

[WaynerN]

Absolutely . Constant Deoxit sessions and knob twisting and button pushing seems to go hand and hand with this era of HK .

I have to do this often as well. I find that getting into the control knobs and switches to apply Deoxit is next to impossible without a partial tear-apart. I have one channel (left) that will occasionally cut out. A flip of the selector switch and the monitor switch does the fix. Some rainy day............

BTW, my 655 is powering my AR-3 speakers. What a combination!