Hello, I have a Pioneer GM-X334 that I think may have some sort of thermal problem. It mutes the audio when the volume is turned up or when the bass hits. The audio is clear but all four channels are affected and the audio is temporarily muted for 2 seconds then it comes back on then off again until I back the gain or volume down. It seems like a low voltage/current problem but right now I am bench testing it with a 13.6VDC@6AMPS power supply into an 8 ohm speaker and the input voltage stays rock solid at 13.8 at the amps terminals all the time. Visually, all components look good but in the 15V regulator section, the two power transistors Q960(Part#D2395), and Q961(PN#RB1566) are running very hot to the touch. I can only hold them for 3 or 4 seconds. I tried an old pyramid amp on the same power supply and cables and I can get far more output out of it. Any suggestions will be appreciated.
(SOLVED)
I was about to post the above thread last night but something told me to take the board out and check the pcb traces on side B. I discovered an open trace connecting capacitor 220uF/10v (C651 on service manual) to 100K resistor (R651). I soldered it back together and the amp plays normal again I have no idea what would cause the trace to open up and there wasn't any burn marks there. However, the two power transistors that I mentioned above are still very running hot with a single 8 ohm speaker connected. The audio power transistors, and power supply FETS, run nice and cool though. Is it normal for these pass transistors to run hot to the touch? I would feel more comfortable adding a heat sink to them.
(SOLVED)
I was about to post the above thread last night but something told me to take the board out and check the pcb traces on side B. I discovered an open trace connecting capacitor 220uF/10v (C651 on service manual) to 100K resistor (R651). I soldered it back together and the amp plays normal again I have no idea what would cause the trace to open up and there wasn't any burn marks there. However, the two power transistors that I mentioned above are still very running hot with a single 8 ohm speaker connected. The audio power transistors, and power supply FETS, run nice and cool though. Is it normal for these pass transistors to run hot to the touch? I would feel more comfortable adding a heat sink to them.
It's common for linear voltage regulators to operate at high temperatures. This is a weak point on a huge number of amplifiers. You can add heatsinks.
Yes I plan to cut some aluminum stock I have lying around and bolt it up to the transistors.
10 years ago I used to run the same amp with the back plate removed and had a of pc fan blowing on the board to cool it down but the heat sinks should do the the trick now.
10 years ago I used to run the same amp with the back plate removed and had a of pc fan blowing on the board to cool it down but the heat sinks should do the the trick now.
If it's not really lightweight, you'll need to provide additional support for it so that it doesn't stress the pads or the legs of the transistors.
The transistors are arranged side by side on the board but have some capacitors behind them so the sink cannot be very deep. I think I will use a rectangular piece about 1/2"High by 1.5"Wide by 1/4"deep. Essentially it will be look like half a stick of gum. It should be fairly light and those transistors look beefy enough to support it by itself.
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