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ryley_999 12th June 2012 09:37 PM

troubleshooting old pionner GM-H100 :confused:
i got an old pioneer gm-h100, he said he couldnt get i to turn on,

well i fix a few cold solder joints, and fixed up the remote turn, now my problem is, when i connect it to the car battery, it turns on, but i get no sound at all,

BUT when i connect it to my little 12 volt 4 amp supply, it make sound, both channels work, but they distort when it get turn up, very low volumes it sound fine when i turn it up it get very distorted,

also when i only have one speaker hooked up to one channel, i can turn it up louder then when i have a speaker on both channels connected,

another thing i noticed was, when i hook up the power from the 4 amp supply, the the volts Drop down to 9.5-10 volts, with no load on the amp. and i have connected this psu to many other amps and i was able to push alot more power then what im getting now,

so i was wondering if there is maby a drain somewhere on the power supply in the amp? rectifiers, caps?

also when i check the output of the switching transistor i get no reading, when i check the ~ legs on the rectifier. i get nothing, but when i check the +&- legs i get about 7-8.5 volt,

sorry if this is a dumb question with a simple anwser, i figured i should ask people who know what they are talking about b4 i start tearing into it

plz and thank you

ryley_999 14th June 2012 01:24 AM

well i know ur gonna think im weird for trying this, but i pulled out the full wave rectifier, turned the amp on, and obviously i dont get any sound, LOL but, now the switching transistors don't heat up like they used to, b4 when i turned it on, they would get so hot within a few seconds i could burn myself on them ( yes they are on a small heat sink), but now they barely heat up with the rectifier out, also the voltage drop at the power termanals are gone, voltage stay pretty much the same,

also i forgot to mention in my last post with no load or signal hooked up to the amp, just the power and the amp turned on, its pulling about 3.6-3.8 amps. too me that seems like a bit much for no load, thats why i im thinkin there is a drain somewhere, i pulled the caps, tested them, none are shorted or even swollen. i checked the outputs they are fine, i haven't pulled the drivers yet because i cant see them causing the amp to pull almost 4 amps with no load connected,

Tekko 14th June 2012 05:06 AM

This thread should be moved to the car audio section.

tiefbassuebertr 14th June 2012 11:51 AM


Originally Posted by Tekko (
This thread should be moved to the car audio section.

No, because the only difference to home audio and public address amps is the power supply.
I think it is the same amp model than this:
FS: Pioneer GM-H100 Non Working - Car Audio Classifieds

First step in such cases is the disconnect of the SMPS. Connect instead this a normal power supply (toroid transf., rectifier and caps) with the same secundary voltage than the internal SMPS.
Second step is the disconnect of all the output power devices - go to
Now only the Transistors Q13/15 and Q14/16 provides the output current.
If now you can hear music (only low volume possible) and the voltages without music inside the amp are right, the failure is present either at output power devices and/or the SMPS. Otherwise you must check the front-end (LTP, VAS Vbe multiplier).

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