Dangun Feveron PCB sound problem.

I picked up a Feveron PCB from a member here and the sound isn’t working correctly from it. You can hear the music but the speach has kind of a hiss to it and the regular in game sounds a so low you can hardly hear them. Told him the day I got it in the mail (Saturday) after trying it out. He sent me another one out on Monday. Ok I got it today and that one works fine. I want to help him out with the one that doesn’t work so……. I looked at each of them and found that the incorrectly working one as a few things different from the one that does work. First I noticed that the sound amp has been replaced. Second there is this solder bridge between these two pins of this chip.






And this is the other thing. This cap solderded here.


Like I said I hope to help him out with this board if I can before I send it back to him.

No help on this one?

It seems that there may have been an attemped (unsuccessfull) repair carried out on this board.

The ceramic cap has been added to filter noise on maybe the 12 volt supply to the audio output IC. The IC was probably replaced in an attempt to fix the distorted sound.

Is that the Z80 with the pins shorted ? It may be intentional, (it looks too blatant to be an accident), but doubt it unless its some hack.

What is the proc IC type and what pin numbers are shorted together.

The chip is a TMP68HC000P-16(on the good board) The chip on this one doesn't have any numbers on it. Looking at it from the parts side of the board form the notch in the chip it is the bottom row of pins 17 & 18

lill-c said:

The chip is a TMP68HC000P-16(on the good board) The chip on this one doesn't have any numbers on it. Looking at it from the parts side of the board form the notch in the chip it is the bottom row of pins 17 & 18

Click to expand...

OK I will check the pin out, in the mean time remove the short and see what happens

lill-c said:

Looking at it from the parts side of the board form the notch in the chip it is the bottom row of pins 17 & 18

Click to expand...

Bottom from the LHS ?

Pin #one is top LHS looking at the IC with the notch on top (from the parts side).

Yes notch up and left hand side it is pin 17 & 18.

That's a short between the halt and reset pins on the main CPU. Looks odd but not related to sound I think. The cap is on the speaker negative (jamma pin L). I would try to bypass the amp entirely and tap sound from the volume pot and see if the distortions disappear.

MKL said:

That's a short between the halt and reset pins on the main CPU. Looks odd but not related to sound I think. The cap is on the speaker negative (jamma pin L). I would try to bypass the amp entirely and tap sound from the volume pot and see if the distortions disappear.

Click to expand...

I tried to just hook up a speak up to the pins on the pot. I got no sound. Should I pull the pot off the board?