C128 CR ASSY 250783

Discussions for CBM PET, VIC-20, SX64, C16/+4 and Commodore 128 systems
Borat
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C128 CR ASSY 250783

Post by Borat » Sun Dec 11, 2016 1:58 am

I've searched everywhere and cannot find any significant info on the CR version of the C128 -- ASSY 250783.

Does anyone have a schematic or any useful info on this board? All I know is it uses the 8580 SID instead of a 6581 and the component layout is significantly different. It also does not fit correctly into a "normal" C128 flat case, due to the board being smaller and therefore the screw holes do not line up. I have to assume that there was, at some stage, a specific case for the CR version or perhaps one with various screw hole positions.


Image



JWag
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Re: C128 CR ASSY 250783

Post by JWag » Wed Dec 14, 2016 5:59 pm

Fascinating. The bodge wire actually has silkscreened path and endpoints ("JW"). I wonder if that's Audio In or Out. And are those protection diode packs by the game ports?

JWag
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Re: C128 CR ASSY 250783

Post by JWag » Wed Dec 14, 2016 6:26 pm

At a cursory glance, the 128DCR schematics on Ray Carlsen's site seem to match up. The RAMs, protection diode packages (DP1, DP2, etc.) and the circular option jumpers near the character ROM seem to line up nicely with the schematic.

I've checked a dozen or so details on your photo with that schematic and it's at least very close.

Aw, they replaced Bil Herd's wacky 12V Z80 clock driver with some paralleled 7407s.

Borat
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Re: C128 CR ASSY 250783

Post by Borat » Wed Dec 14, 2016 10:17 pm

Thanks for the info. The schematic is similar to the DCR, in fact I used the DCR schematic to fix a fault on the audio out. C85 (beside the JW) was reading high ESR ohms. I replaced it and all is working fine.

I also found this thread which has some good info about the CR board.

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