Did you try checking the levels at the pins with the chip out of circuit?
Probably should troubleshoot the board without the chip before you toast
another one.. :)
Kurt
> I'm not sure if my first post went through. Sorry if this gets posted
> twice....
> Can someone give me some ideas?
>
> *******************************************
>
> I've been working on a Midway Space Invaders and need help getting the sound
> back. Normally I find this to be a fairly easy fix but I'm running into
> some difficulty here. When reading the audio voltage, I'm only getting
> about 6.5 volts when it's supposed to be around 18v unregulated. Last night
> I noticed that some of the pins on the audio amp were shorted together, so I
> replaced it with a brand new LM1877N audio chip. The chip was ruined and
> some of the pins were, again, shorted together. I believe something is
> drawing in too much current and killing my poor chip.
>
> The power supply board is known to be working, so I'm pretty sure I can
> eliminate it (although I'm not so sure about the flakey wiring harness).
> I'm pretty sure the problem is in the amplifier section. I pulled out the
> chip and tried to find any shorts in that section and replaced a couple (but
> not all) of the tantalum capacitors and the nearby LM3900 chip. After that
> I ruined yet another LM1877 chip! This is the point where I have to admit
> my troubleshooting technique is a little limited and I don't want to destroy
> any more chips. Fortunately they're only about a buck a piece at Jameco.
>
> Can anyone offer me some suggestions? The speaker checks out ok, by the
> way. - And yes, I'm putting the amp chip in the correct way. The audio
> board schematics can be found here...
> http://spaceinvaders.retrogames.com/html/index.html
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Received on Thu Dec 12 12:17:03 2002
This archive was generated by hypermail 2.1.8 : Tue Dec 02 2003 - 17:51:31 EST