Re: Battlezone repair log

Has anyone ever tried the "Full Screen View" trick where you disable
WINDWBLK by making it stuck high? It's sometimes neat to see the flying
tank bits and dropping missiles outside of the normal window. I was
thinking of adding a toggle switch for that. Maybe putting it behind
the coin door.

Matt

On 10/23/2013 12:31 PM, Joel Griffin Dodd wrote:
> Some great Sherlock Holmes style investigation there well done, thanks
> for the read.
>
>
> On Tue, Oct 22, 2013 at 11:38 PM, David Shoemaker <davids@oz.net
> <mailto:davids@oz.net>> wrote:
>
> Board would work sometimes, glitch others, also intermittent math
> box errors. Just generally unstable.
>
> Replaced all the rom sockets and CPU socket with new. Also
> replaced the headers pins on both the CPU and math box boards with
> new square pin .156 headers.
>
> Board now runs stable, no math box errors (I didn’t replace the
> interconnect cable pins, but with the new larger surface area for
> contact they seem to be fine.)
>
> Board works fine on bench (with o-scope) but in the upright
> periscope model cabinet no picture.
>
> This one took me a couple hours to figure out, had to pull a spare
> monitor out of storage to ensure I wasn’t crazy.
>
> The harness I have on the bench is a salvage from a trashed out
> cabaret cab. It has a jumper between pins L & P on the CPU edge
> connector. This puts the board into “Invert” mode for direct
> viewing. The analog switch at E10 was bad (replaced with DG201).
>
> Added a switch into my bench harness to be able to exercise this
> invert circuit.
>
> Also found that maxim IC has a DG201 pin compatible part the
> MAX4511. I have a couple samples on order to see if they work in
> this application.
>
> Replaced E10 (DG201)
>
> Board z channel working only partially. Many retrace lines are
> visible, adjusting the monitor brightness and contrast is not able
> to clear the problem.
>
> Used the scope to trace around the z out circuits. Had a moment
> of wild goose chasing the DVY4 signal which doesn’t move an
> appreciable amount in self-test. Verified the same signal with a
> good board. As the resistor ladder dac appeared to be all good I
> starting looking at the Q7,8,9 transistor chain to see if that was
> acting up. Q8 didn’t seem to be doing much.
>
> Traced this back through N9 (ls02) to the shift register at P9
> (LS164). A(1), B(2) and clock(8) were all good but QE(10) &
> QF(11) were both dead. Piggybacked a new chip on top and got some
> signal which resulted in some z channel effect on the self-test
> screen.
>
> Replaced 74LS164 & P9 and now have full z control.
>
> Badly unstable screen, vectors jumping around all over.
>
> Found .047uf poly cap at C59 was broken on one leg.
>
> Replaced C59 and screen stable.
>
>

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Received on Wed Oct 23 16:47:39 2013