Search found 1298 matches

by Pr0f
Tue Jan 23, 2024 2:36 pm
Forum: Hardware
Topic: Minerva Mk2 Remake
Replies: 41
Views: 2488

Re: Minerva Mk2 Remake

Is this to include the I2C components (clock and I2C output) ? If so could I suggest an I2C buffer chip be added ?
by Pr0f
Tue Jan 23, 2024 10:21 am
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

The SRAM chip does not need or use any signals from the 2 Sinclair ULA chips ZX8301/ZX8302 - it gets it's select signal from the ICL ULA, but this is gated with FC2 (high in supervisor mode) so that the RAM can only be accessed when Selected by address decoded by the ICL ULA and FC2 indicating Super...
by Pr0f
Mon Jan 22, 2024 10:31 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

The other one comes from the NAND gate - with FC2 and the CMOS RAM enable from the ICL ULA as the inputs to the gate - so the RAM can only be accessed in supervisor mode.
by Pr0f
Mon Jan 22, 2024 10:19 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

I think that comes from the drain of FT5 - controlled by the powerdown on the 15 way connector, that FET will ground the /CE input when powerdown is at 5v (this signal goes to multiple places) - the drain has a load resistor connected to the diode junction from 3v lithium, and diode from 5v, so eith...
by Pr0f
Mon Jan 22, 2024 6:08 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

The ROMS are I think in 3 parts - the first 64K are a combined OS ROM - so that's ROM A and B ROM C has a header like other application ROM's - so I wonder if this OS Extension is handled as an application ROM - ROM D seems to be the one that may have different code in it and seems to be mostly prov...
by Pr0f
Sun Jan 21, 2024 1:44 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

Seems odd you get a ROM fault when it had worked before you put it into storage. I noticed that on both my daughter boards - 3 of the ROM chips are mask ROM's and the last one closest to the processor - the one that's in position '7' of the LS137 decode at address 0xA8000 - is an EPROM. It would be ...
by Pr0f
Sat Jan 20, 2024 10:04 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

I'm wondering if this is a fault with ZX8302 (9v battery) power circuit?
by Pr0f
Fri Jan 19, 2024 10:10 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166841

Re: ICL OPD

On the WD1770/WD1772 question - https://www.bing.com/ck/a?!&&p=a82800f7a09cfd2aJmltdHM9MTcwNTYyMjQwMCZpZ3VpZD0zNWNkMTA1ZS1hMmVmLTY3N2ItMTZhNC0wMzZjYTNkNzY2OTUmaW5zaWQ9NTQ5Mg&ptn=3&ver=2&hsh=3&fclid=35cd105e-a2ef-677b-16a4-036ca3d76695&psq=WD1770+WD1772+differences&u=a...
by Pr0f
Fri Jan 19, 2024 7:53 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166841

Re: ICL OPD

My bits have arrived to put the power supply / video adaptor board together - so that will be done this weekend - the box is big enough to accommodate a 3.5" floppy - and I found my 5V only TEAC 1M floppy drive so that will be pressed back into service for the OPD. Next steps: Test the PSU / VI...
by Pr0f
Mon Jan 15, 2024 4:31 pm
Forum: General QL Chat
Topic: Possible QL Is 40 event, UK
Replies: 14
Views: 1326

Re: Possible QL Is 40 event, UK

I'd certainly like to attend - as long as it's not one of the 5 weekends I have to work, or one of the few weekends I am away on holiday.


The last ever event I attended was a Computer fair in London with a reasonable QL presence - and that was back in the eighties!