[Coco] Weird CoCo3 problem...

[Bob Devries]

Brian,

from your description, I'd say that the Coco3 motherboard has been hacked 
and/or modified.

I'd be looking to restore it all to stock standard, with only those mods as 
were required for the 512k upgrade. Look particularly for broken traces on 
the motherboard.

Regards, Bob Devries
Goulburn, NSW, Australia
(soon to be back in Las Pinas City)

--
Besides a mathematical inclination, an exceptionally good mastery of one's 
native tongue is the most vital asset of a competent programmer.

Edsger W.Dijkstra, 18 June 1975

----- Original Message ----- 
From: "Brian Blake" <random_rodder at yahoo.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Saturday, January 02, 2010 6:05 AM
Subject: [Coco] Weird CoCo3 problem...


>
>
> All of these new developments on the CoCo front finally lit the fire under 
> my arse to set up real hardware again. Besides my repack project, I have 3 
> other CoCo3's, two with 512k upgrades (one C9 and one PBJ) and one 128k. 
> The one with the C9 upgrade works fine - can load and play Sockmaster's 
> Donkey Kong.
>
> The one with the PBJ upgrade, not so... At boot, it comes up as it should 
> with the proper display. However, any floppy commands are met with no 
> response from the floppy drive (with an FD-502 controller) at all. Almost 
> like the drive is off. The drive responds as it should in the other two 
> machines. Upon removing the top case and k/b, I saw two wires, each had 
> been soldered to opposite sides of R23. Now, under the keyboard, is 
> another wire with alligator clips on each end, and the clips are holding 
> on to the bare end of the wires soldered to R23, effectively bypassing the 
> resistor. I'm looking for the PBJ instructions, pretty sure I have them, 
> to find out if this is called for. I can also see where C65 & C66 have 
> been cut and re-soldered. I have reseated the GIME and the PBJ memory 
> chips, and cleaned the 40 pin connector.
>
> Any other suggestions? My 100MHz o'scope bit the dust so I don't have that 
> tool any more (anybody have a CRT for a Leader 3 channel 100MHz scope??)
>
>
> Thanks,
>
> Brian
>
>
>
>
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