First check that the power to the cpus and other chips is a good 5V
Dc (4.95 will do) then check the clock signals on the CPUs inputs and
VIC out puts (also at the crystal) - then check for hot RAM or with a
O'scope check the signals on all the ram chip legs - if one set looks
strange by comparison suspect it first. --Ray
>Hello all,
>
>I've been tinkering with Georges prototype C128 of late. It's a REV0
>motherboard without an FCC sticker, but with a serial number of 145, and
>REV2 and 3 EPROM ROMs. I replaced the three broken keys from the popular
>G.P. collection photos, and made a stab at getting it to boot up. That,
>however, has proven difficult.
>
>The basic symptom is a black composite start-up screen. Using a working
>C128, I managed to confirm that all the socketed chips from the prototype
>machine are OK. This includes the ROMs, both video chips, and the 8722
>(MMU?). The MMU is actually the only chip I noticed as being an unusually
>old revision, being a REV1.
>
>Anyways, I'm a bit at a loss. I'm not very excited about the prospect of
>socketing memory and processor chips, just like I would ANY old C128, in
>order to fix it. The only other clue I noticed is a particularly hot
>running Z-80, compared with the Z-80 in the working C128 I'm using for
>testing.
>
>Any advice is appreciated, though I'm still wondering if doing anything at
>all is a good idea, since any changes would put this motherboard in the
>hands of a solderer who is merely fair at best. :)
>
>- Bo
>
>
> Message was sent through the cbm-hackers mailing list
--
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|Raymond C. Bryan 651-642-9890 vox | The battle is sometimes |
|Raymond Computer 651-642-9891 fax | to the small for
|
|795 Raymond Ave -email: raycomp | the bigger they are |
|St Paul MN 55114 @visi.com | the harder they fall. |
|USA Amiga - Commodore | -- James Thurber -- |
http://www.raymondcomputer.com
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