TRS-80 Model III stopped responding

Tony Duell ard.p850ug1 at
Wed Nov 6 04:23:28 CST 2019

On Wed, Nov 6, 2019 at 6:00 AM rescue via cctalk <cctalk at> wrote:
> Well, it is something with the supplies.  I tried the floppy power
> supply in place of the system one, and got a Cass? prompt !
> Then I switched back, and got a Cass? prompt !  GRRRR !   I'm still
> digging.... maybe something failed and if I mount it back up it will
> stop working again (once the ground pads are grounded on the back of the
> supply ?).

Bad connections somewhere? The stiff ribbon cables between the CPU and
FDC and RS232 boards are notorious for this in my experience. Or at the
Molex connectors on the PSU.

A Model 3 CPU board needs all 3 outputs (+5V, +12V, -12V) from the PSU for
the DRAMs (4116).


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