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by Pr0f
Thu Jan 11, 2024 10:35 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

Actually - I just noticed it's marked all your capacitors as 1pF. I think I get the circuit now, and I think I know why it might not be oscillating - the 2 74LS04's that are wired around the crystal should have some feedback resistors between input and output - this will bias them into the linear mo...
by Pr0f
Thu Jan 11, 2024 10:05 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

Trying to understand the circuit around the crystal, it looks like a 1pF capacitor in the feedback loop with the crystal?
by Pr0f
Thu Jan 11, 2024 9:56 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

And I agree Stephen - the OPD is strange!
by Pr0f
Thu Jan 11, 2024 9:55 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

Is David still contactable?
by Pr0f
Thu Jan 11, 2024 8:25 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

On the subject of programs - does anyone have any information / ROM cartridge images for any sofware that provides serial interface for the ICL OPD? I know there was the 64180 based CPM module which supported disks and a serial port, I also know there was a unit based on a 80C31 which provided a DB2...
by Pr0f
Wed Jan 10, 2024 10:08 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

The issue with BASIC is that it doesn't fit in the 32K ROM slot size. The Telestore hacked things and fitted it in two 32K ROM slots. RAM expansions have to pretend to be ROMs in the ROMpack and then have code which hacks the OS into ignoring the "BAD ROMs" and telling where the extra RAM...
by Pr0f
Wed Jan 10, 2024 9:42 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 167390

Re: ICL OPD

That's great news ! I am waiting on some parts to get power and video working for my base unit (I got no monitor), and once I've got the setup at least giving me some video - I plan on porting ICL basic to a ROM and seeing if it can be made to be available without having to be loaded up from cartrid...
by Pr0f
Wed Jan 10, 2024 11:13 am
Forum: Hardware
Topic: Solid State Microdrive Cartridge?
Replies: 18
Views: 1316

Re: Solid State Microdrive Cartridge?

That was also my understanding - that if the QL was writing data - it would be present on the head, and would not be there if we were reading - it would expect the tape to be providing it. Since the QL would normally spin up the tape before attempting to write anything, and as I understand it - it n...
by Pr0f
Tue Jan 09, 2024 3:04 pm
Forum: Hardware
Topic: Solid State Microdrive Cartridge?
Replies: 18
Views: 1316

Re: Solid State Microdrive Cartridge?

Or perhaps a custom magnetic, but it would need to be 2 tracks. The other issue is power to the unit, as it would need to be battery powered most likely and a likely power source would be a 3v lithium cell. I suppose the motor would only need to drive an encoder wheel or something to give the tape m...