Gorf background sound

joseph77

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Just started digging into the Gorf I got and noticed there is no backround sound. Any particular areas I should look at on this?
 
I'd start by checking the amps on the tiny amp board. One of them could have died. Next, it could be one of the custom audio/input/output chips on the ""game board".

Edward
 
All three of the Gorfs I have had ended up having some kind of audio problems. I agree with Edward, definitely look at the amp. If you want to verify if its the TIP31 swap them side to side and see if the problem moves.

All three of mine needed a TIP31 on one of the channels.

2 had blown speakers. The voice coil was seized solid in both cases. The channel with the blown speaker was the same as the one needing a TIP31 in those cases.

The AMP board also has a 2N4403 in each channel. I also ended up replacing it on the last Gorf I had. In this case I replaced the blown speaker and the associated TIP31 and had sound. While letting it burn in it would randomly crash and lock up after a hour or so. I could disconnect the AMP and it would run forever. I also want to say that the channel I had fixed always had a constant tone coming out over it during the crash/lock up. I swapped in a new 2N4403 on a lark and never had the problem again. My assumption was it was failing, overdrawing current from the supply at some point (drive to ground???), and crashing the board because the voltage dropped. Total guess. I did not go back and dig into it to understand the detail of the circuit once it was running.

Some notes I made to help me isolate a given channel by sound.

The volumes knobs. The left is channel 2, right knob is 1.

Channel two, among other things, holds the background "dum dum" sound on Astro Battles as well as the enemy laser sound on Laser Battle.

Channel 1 is the Gorfian voice (when the game talks) and has the fire sound of your ship.

I do not recall which speaker is which. Once you figure out which channel you have working you can derive the speaker for it.
 
There's also a couple tantalum caps on the amp board.....these, too, are known to take a shit.

Edward
 
Did not get a chance to troubleshoot it tonight but it is the channel 2 sounds that are not working. If I wanted to rebuild the audio amp board who or where is the best to purchase the parts from?
 
I tend to order from Mouser and Jameco. I don't recall anything super exotic on there. The transistors, some diodes and resistors, and the caps Edward mentioned. Jameco may have it all.
 
Other channel fixed?

You ever figure out your other channel?
 
I had the same problem with my Gorf. No sound when the invaders were marching left and right. I metered the parts on the sound controller pcb. You can refer to your manual on the correct reading on each part. I found a 330 ohm resister that was showing a short on my ohm meter. It should have read 330 ohms, but it was metering at 3.3 mega 0hms. Pulled the resister off and replaced it with new resister. Fired up the game and now the sounds are working again....Yea!!!

Then half way into the first screen my fire button stopped working........WTF!!! Now I am trying to fix the fire button problem......time for more research......good luck on getting your Gorf up and running.....don't give up...

Update - I found the problem with the fire button. It turned out to be a cold solder on one of the header pins on the controller pcb which connect to the wire harness coming from the fire button. Reflowed the solder on the header pins. Plugged the molex connector back on the pins and all is working again.
 
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