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Slack's World
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August 20, 2014, 01:48:50 AM

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by Slackmaster Stan

Problem: Brought home a Xevious that I pieced together from the local warehouse. Worked fine except for the sounds which most of the time play at a higher pitch with a thinner sound than it should.

8/13/2006, I swap a different Audio/Regulator II-01 board that I have. Second board is dead, swap them back. Check voltage and adjust the 5V to about 5.1 as found on the edge connector of the filter board. No impovement.

Inspection of board reveals a SN74LS283N (4 bit adder)chip has corrosion. I tried burnishing the pins and reflowing the solder. This seemed to help and I thought I had it fixed, but the sound was going in and out.

Checked the schematics and it definitely appears that this chip is part of the audio circuit, so it is worth further investigation. Close inspection shows that the ground pin is broke in half. Try to adjust and the pin breaks lose. Clip and desolder (with a bit of pad damage).

08/17/2006, I manage to find a board (thanks brit-boy) that I can salvage a M74LS283P (close enough?). I use the heat gun to remove the chip. Worked great, though I wondered if I had toasted the chip. Replace chip, check some traces, get impatient and try out the board. No go, now just clikety sounds. :-(

I try to find some patience and get out the continutity meter and find out that my +5V isn't good. I botched up the pad, so I bridge the connection, check out the rest of the pins...Success! Oops my video is out of wack...Just the vert hold, nevermind.

Solution: Poor ground on SN74LS283 (at 8K), broke pin, replaced chip.

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