π¬π§ Sinclair QL: Part 3 (Issue 6 Replacement Motherboard) [TCE #0560]
19I managed to get a replacement motherboard - turned out to be an Issue 6 board, compared to my faulty Issue 5 board. Swapping some parts made no difference to the Issue 5 board so I'm wondering if there might be a RAM issue - having no idea the best way to investigate, I thought it best to just swap in the newer Issue 6 board (after giving it a good clean).
The Issue 6 board also has a very nice ceramic Motorola 6808 CPU and came with the "JS" version ROM. I removed the RF modulator for the video output (it was a bit rusty) and also replaced the 7805 linear regulator (and heat sink).
00:00 ... Intro
02:00 ... Testing the board
03:15 ... Comparing the Issue 5 and Issue 6 boards
05:00 ... Preparing the Issue 6 board for a clean
05:30 ... The new plan: swap the boards over
06:00 ... Linear regulator 7805 replacement
07:15 ... Dodgy wires discovered under the Issue 5 board
09:12 ... Microdrive cabling reconnection
16:18 ... Finally, testing the machine
20:18 ... Channel thanks & Outro
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From Part 2:
The replacement keyboard membrane and some apparently re-felted Microdrive cartridges have arrived so it's time to look at this fellow again.
I replaced the membrane pretty easily but it still boots to a white (well, grey IMHO) screen ... I had thought maybe I had to press f1 or f2. There is also no activity on the Microdrives that I could see.
Pressing the [RESET] button still elicits a key typing noise, so something seems to be working.
The machine came with the "JM" version of the Sinclair QL ROM which appears to be the penultimate version from Sinclair (followed by "JS"):
https://dilwyn.qlforum.co.uk/qlrom/index.html
I tried installing the Minerva 1.98 (with QLAN I/O fix) by splitting the 48KB ROM into 32KB (for a 27256) and 16KB (for a 27128).
http://tfs.firshman.co.uk/ql/fminerva.htm
So some further troubleshooting is required, including a proper look at the DRAM chips ... yay, possible de-soldering required.
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