Help - Asteroids totally silent no sounds or hum from speakers

action76

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Help - Asteroids totally silent no sounds or hum from speakers

I got an Asteroids cab recently and it works fine except there is no sound whatsoever. I do not hear a hum or hiss from the speaker. The AR board is fine because I tested it in another machine and the sound worked fine in it. I am assuming the problem is on the PCB now? I am totally new to Asteroids repair so I'm not sure where to look. I can do board work no problem I just need to know what to test or replace. Any help would be greatly appreciated.

Thanks,
Stephen
 
I'd first check the volume POT inside the coin door area. Got connection? Pot is clean? etc

Then I'd suspect the edge connector.

Then, if you suspect the logic PCB, check for damage in the audio output section - cap is missing or broken trace etc ... or the LM324 P11 AMP is bad.

The output AMP needs +22V. So check that.

If you have test equipment, look at signals going into pin9 of P11 and/or out of pins 8 and 14.
 
What VC said. Asteroids has dedicated circuits on the game PCB for each of the sounds, so there can be a lot of possible issues, though the most likely (if all of what VC said are ok), is the LM324 amp in the upper right corner (above the edge connector), which is the main preamp that sends the mixed audio signals to the AR, where they are power amplified to drive the speakers. You can socket and replace it, if you are handy with soldering.

Definitely make sure your voltages are correct first though. Also, make sure none of the caps in the upper right corner of the board are broken, cracked, or missing (which is common, as some of them are large, and stick out). Google up a high-res pic of another reference board, to compare the locations of the larger caps.
 
Thanks VC and andrewb! I will start looking at these things when I get a chance. This helps tremendously.
 
check speaker coil wires, swap in a known working example

LOL - yes, we've had many threads where it was just a bad speaker. Or even a mouse-eaten speaker. Open up the marquee area and be ready for a surprise. :eek: (might also check wires at the speaker)
 
The speaker was not hooked up actually. I hooked it up and it did not work and I tested the speaker on a stereo and it was working. Although It was not an original speaker. It was a 4 ohm speaker. Isn't the asteroids one supposed to be 8 ohms? Also is a LM324AN the same thing as LM324?
 
Speaker impedance doesn't really matter. The TDA2002 amplifiers on the AR are rated to drive down to 1.6 ohms, so pretty much any speaker will work. I'm not sure what the original ones were for Asteroids (as the schematics just say '8" High-Fidelity Speaker') but you'll be fine with what you have.

And yes, LM324AN is the same as LM324.
 
in the past i have tried to repair a blown speaker by first repairing the AR board (that of course didn't need any repairs)

silly me, it never fixes it :-(
 
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