RC2019/03 update 3: Another Video Genie (mostly) repaired

This is part of a series for the Retro Challenge 2019/3.  Visit the index page for all the posts.

Today I tackled the second broken Video Genie (TRS-80 clone).  This one has an interesting home-made mod on it too, which I investigate.

The main repair was quick and easy, but it still has a minor fault that I need to investigate.

Here’s a 21 minute video of my repair:

I’ve now ordered spare parts for a permanent fix to both machines (I had borrowed working parts from other machines for the diagnosis).

From RS I got a couple of brand new Z80s – they are still making them!  Plus some capacitors and transistors to try to fix the power supply circuit for the cassette deck.  I also added some extra transistors for my parts drawer for future repairs:

From eBay I’ve ordered 5 x SRAM chips for the video memory.  I only need two (for now), but as they’re no longer made and readily fail, it’s worth having a few in the cupboard!

This listing is for exactly identical chips as removed from one Genie, so I can be reasonably confident they’re correct.