The Sinclair QL Forum

Nice one

Well done on the progress with the DRAMS - so now probably just a single faulty chip?

The QL motherboard has pin 1 and pin 28 wired to 5V - so the 'expected' A15 signal is not on that pin - instead it's used as a chip select for the ROM's - the ROM's in the QL ROM set - one is active high and one active low - so A15 decodes whether lower 32K or upper 16K rom are selected. Either ROM ...

that could be down to either a ram chip not being writable (Data in on the RAM shorted or open circuit), or to a shorted or open address line on the DRAM chips - the regular pattern also suggests something like this. Such problems are hard to find. As you have surmised - the upper and lower banks ar...

those current draws are favourable. Letterbox - just that a keyboard and LCD screen combo may be a good way to do this - as it's one single case to make - no hinges. The letterbox LCD screens are available with HDMI input - but the resolutions are a bit strange - they are usually 400x1280 or 480x192...

Thoughts from the 40th QL Celebration. It was a late decision for me to attend the 40th Anniversary celebration in Dormagen, but I am glad that I did make that decision. Having been in and out QL ownership over most of those years, but strangely always having a couple of Sinclair products in my hous...

I've used 7V without a problem, not sure about 7.5V - It is dropped by one diode forward voltage (about 0.6-0.7 vols), and feeds the circuit that would normally see the 6V from the batteries. Very fresh batteries could provide close to 1.6V each - giving a voltage of 6.4 against the 6.9 you would se...

The Z88 does have it's own rather clever little power supply that can produce a bit of high pitch wine when operating - usually caused by the small ferrite transformer / inductor on the board being a tiny bit loose. Sometimes a small blob of silicon sealant on it can anchor it to the PCB sufficientl...

I think you've done a great job getting the q68's out to so many Derek, it's attracted a good few people back to the QL scene!

I got one of those kits to see what the dev tools were like. It seems there are a good few design constraints on the pins, so what looks like a lot of pins soon gets eaten up with the dev board resources. I've seen the 20k used to define the Yamaha MSX2 chip, but Peter gets a video controller, a mem...