Irem M-92 Sound Problem

PCB problems and fixes
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Nebula
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Irem M-92 Sound Problem

Post by Nebula »

Dear forum,

I recently got an M-92 board from Irem with the game "In The Hunt" perfectly preserved. I was checked it with my homemade supergun on an LCD TV (it's the only one I can try it on right now) and it works perfectly but the sound coming out of the jamma edge is a very high signal, on the order of 4V, which causes me to have to put the volume knob to a minimum so that the sound is not distorted (a milimeter from the minimum Confused).

I know that this board installed from factory some ELNA electrolytic capacitors that usually fail and leak their acid, so I was willing to change them all, not only to try to solve the problem of sound, but also to prevent future leaking. At that time, it did not look like any capacitor was in poor condition or leaking.

After replacing capacitors, I again tested the board and it seems that the sound has improved a bit, but it is still a very powerful audio signal (and distorting if I go up the volume knob).

In addition, the signal amplifier seems to be overheating (I can not bear to touch the heatsink when the board has been working for a while)

I wanted to ask you if this is normal scenario, if the sound signal should be so powerful and if the amplifier is heated that way in normal operation.

The amplifier that uses this board is a Fujitsu:
http://www.andysarcade.de/data/electron ... mb3730.pdf

Can it be a problem with the amplifier and should I replace it?
Some of you guys that have a M-92 board, could you please check voltages of sound signal on jamma edge?

Thanks in advance!
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