All posts by Craig Southeren

RIFA adventures

I need some 4700pf/300v RIFA caps for Kaypro power supplies, so I ordered replacements from element14.

However, I’m not sure these parts are suitable as they are somewhat smaller than I was expecting. What’s the consensus of the hive mind – can I use them?

UPDATE: consensus was that they are OK to use, provided they fit physically!

Disk drive working

Kaypro #1 wouldn’t boot from a Gotek, but Kaypro #2 is up and running!

Update: the problem with Kaypro #1 was the WD9216 data separator. Swapped this chip with one from another system and disk reads started working.

System-80 working (sort of)

This poor System 80 has been subject to cruel and unusual punishment at the hands of previous owners.

I’ve got the Ready prompt (the equivalent of the TRS-80 Memory Size) but it’s been hard work. All of the 2102 video RAMs needed replacing, as well as several LS157 muxes. I managed to link A4 and A5 when replacing a mux – that cost me a few days.

Pressing Enter gives a screen of full graphics blocks – I think the video RAM read is not working fully. But to debug that, I need to understand what is left of a lower case support mod and (I think) software switch for 32 col mode

Restoring the System-80

The battle for the System 80 has begun!

I started with no video, no CPU activity, and a very bodgy looking 64k DRAM upgrade using 4164s

Fixed the CPU issue by replacing a dead electrolytic in the reset circuit. Video came back when I replaced the cable between the boards.

I’ve reversed the 4164 upgrade and am working on the Drastik.

The time honoured “ROM of NOP” is generating square waves on the lower 8 address lines. Now I need to find where they stop being square!