RE: Techtoolslist Digest, Vol 4, Issue 7

<x-flowed>It's starting to look like a design flaw. The 68B21's RESET line is
simply tied to Vcc through a pull-up resistor. I've now jumpered that
to the board RESET line and I get a clean start up almost every time
(I have substituted a good 68B21 to no avail previously).

Sooo, if this works in the game, another Tech Tip will appear on RGP I guess.

John :-#)#

At 11:51 AM -0600 2/23/05, Robert C. Bullock wrote:
>John:
>
>-----
>However when I replaced the suspect 175, no sounds, and when I put the
>original 175 back in the (now socketed) PCB, I don't get the sounds even
>with the Bugtrap the same way.
>-----
>
>Hmm, the only similar thing I've seen is a bad -5V reg (7905) on Atari
>Roadblasters in the sound section. Putting my logic comparator on one of the
>chips fixed a problem with the scrolling playfield, but killed the sound.
>Take it off, it scrolls again, sound works.
>
>Replacing the voltage regulator fixed it. The voltage on the pulse to sync
>that section of the board was low.
>
>You'll have to Google this or give me a deal on that pinout cart :) and I'll
>dig the particulars back out. This sounds somewhat similar.
>
>
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</x-flowed>