Re: LL PCB repair

Would be totally awesome Steve !

Remember this baby has been converted to Asteroids with a bootleg kit BITD so I guess I'll need Asteroids bootleg sigs ;)

However....I just diagnosed my very first fault on an arcade PCB with my Fluke. I'll immediately will admit that I could have found the issue just using my eyes too......

Hooked up my 6800 to 6502 converted pod, powered up UUT. Fluke says UUT power is not OK. I check on the board and indeed it's only about 4,6V

Nice, that works :) Cranked up my test switcher PSU to 5,1V on the board and no more complaints from the Fluke.

So first things first: Bus check. Response => pod timeout Bad UUT clock.....touch the 6 Mhz test point with the Fluke probe and it sticks high. Reset the board and it sticks low and whatever I do it sticks low.

Mmmm so we got a clock problem, let's see where that crystal is.......mmmmm....should be very near that test-point but all I see is........two holes in the board.....the crystal is missing or broke off :P

Guess I'll need to dig one out or order one....gonna be hard to get the exact correct frequency AFAIR.....but OK I feel both happy and a bit stupid for not noticing this right away :)

Cheers, André

Op 21 feb. 2013, om 19:05 heeft xray2 (Steve) <xray2@arcadehacking.com> het volgende geschreven:

> Andre,
>
> I'm out on business travel right now but can send you my notes for testing the LL board with the fluke when I return home this weekend. It's probably not a lot but I have the checksums, memory and I/O ranges mapped out. If you think it will help I can convert them from paper to electronic for you.
>
> Oh, and YES, you only need +5 on any of the vector boards for testing. I believe asteroids and newer require an about 11.3v on the input of one of the tl082 opamps to drive the output high and start the clock. You can't damage anything by not applying the +/-22.
>
>
> -- Steve
>
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André Huijts
andre.huijts@upcmail.nl

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Received on Thu Feb 21 17:36:02 2013