π¬π§ Sinclair QL: Part 4 (VGA Video Output) [TCE #0566]
43Thanks to #PCBWAY for their ongoing support ... https://www.pcbway.com/
Let's try to get better video output than Composite PAL by trying this QL-to-VGA converter: it converts the QL's 512x256 resolution to 1024x768 XGA where one QL pixel = 2x3 XGA pixels.
Normally I would just "dump" the RGBS signal into a GBS8200 but this is a simple little converter using a Raspberry Pi Pico and some resistors designed just for the QL:
https://github.com/holmatic/video_if_ql_vga
I also have some other PCBs that I am waiting on parts for:
[1] 512KB internal RAM expansion:
https://github.com/Silveriomrs/QL_512kb_External_Expansion
[2] MicroDrive & cartridge replacement:
https://github.com/Silveriomrs/micropicodrive
00:00 ... Intro: repainted Fujitsu Siemens keyboard
01:58 ... Thanks to PCBWAY
04:00 ... RAM expansion & MicroDrive replacement
06:10 ... QL-to-VGA video converter
08:12 ... Building it
10:30 ... DIN video cable
13:08 ... Checking Composite PAL video output
13:50 ... Checking RGBS video output
16:09 ... Channel thanks & Outro
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From Part 3:
I 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).
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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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