• 04-02-2006, 07:14 AM
    Scott in Jersey
    Help fixing my HK PM640 Vxi Integrated Amp Please
    Hello folks. I am new to this forum so please excuse my ignorance to any unkown help request protocols.

    Here's my problem that I'd like advice on how to fix. I have a Harman Kardon PM640 Vxi High Voltage High Current Intergrated Amplifier which has a barely audible left channel. Makes no difference if using A or B or Both speaker selector settings or any of the inputs (CD, Tuner, etc.). I have to turn it up about 60% of max to get any sound from the left speaker at all. Which normally I would never do given the power of an HK amp. I am running Ohm Walsh Cam - 32 speakers and the amp is set to 8 Ohm mode (has a 4/8 ohm setting option). I have tried both the 4 & 8 ohm speaker settings & the problem still exists.

    I have openned up the chasis to look for blown fuses, etc. but cannot see anything that looks broken. I also have no idea what I am looking at. I have a local repair shop that could probably fix it for an arm & a leg, so I thought I would ask you audiophiles first.

    Thanks for any advice! - Scott in Jersey
  • 04-02-2006, 07:32 AM
    First you need to do a little more isolation to verify that your assumption is correct. You are assuming that the problem is with the left channel of your HK.

    Swap your speaker leads. Unplug the leads going into the left speaker and hook them up to your right speaker. Of course, you must unplug the leads going into the right speaker and plug those into the left one.

    If the problem switches to the right speaker, then either it's the speaker wire or the amp. If it does, then swap the speaker connections at the back of the amp and see what happens.

    P.S. There is no "unknown help request" protocol. Just ask an honest question and you should get an honest answer.
  • 04-02-2006, 07:59 AM
    Scott in Jersey
    Update on HK pm640 Vxi Int Amp Testing
    Thanks for the suggestion Jeskibuff. I swapped the speaker leads left to right & right to left and had the same problem just from the right side (when hooked up to the left speaker lead on the amp). I have tried both cheap speaker wire (~22 gauge) and my high end 12 gauge, same result. I have also tried other speakers (DCM TF500s) and had the result. I have also tested the Sony CD player, Onkyo Integra Tuner & Apature HD AV interconnects using a old Sony Integrated Amp and everything worked fine from both channels.

    So I am pretty certain the problem lies within the HK Intergrated Amp left channel. Any further suggestions would be great appreciated. Thanks again!
  • 04-02-2006, 08:06 AM
    Well, if there's no circuit protection reset button or fuses, likely it's an output transistor that has failed. Most likely you will need to pay the piper to have it serviced by a qualified technician. The most important thing is that you've confirmed the problem is with the HK, instead of possibly misdiagnosing the problem and paying a technician to tell you there is nothing wrong with it.
  • 04-02-2006, 10:08 AM
    I would e-mail HK service and find out what they may think. When I have had a problem with a Rotel product I contacted Rotel and they recognized the problem from my description since other units had been repaired for the same thing. It was repaired cheaply because they did not have to spend a long time diagnosing. HK will know the unit and may very well be cheaper.