Recent content by Gary C

and if you use the TEXT command, it only updates one of those banks and screen updates are a lot faster. but only for text.

So the 74LS244 was actually a dud, data was passing at variable voltages regardless of the gate voltage and seemed to change with temperature. Replaced and that bit now works fine. Haven't tested the cassette ports yet but I do have an issue. One unit when powered on just locks. Turn it off...

Interestingly, the PCB disk drive interface calls for a SN54LS08 rather than a 7408. I know the basic differences but I wouldn't have thought a military grade logic chip would be needed over a standard 74 ? Maybe a 74LS08 might be too slow, but I can't see the extra current draw of a 7408 being...

I had (and lost) one of those :( Admittedly it belonged to work Mind you, I would love one of RS's alternatives !!!! £5.88 for an alternative to the fluke probe, yes please ;)

Got given two of these machines in a poor state. Cases open, keyboard hanging out and no PSU or video cable. PSU nocked up from an AT PSU as this machine needs a -5V as well as a +5V and +12V First machine powered up on UHF and my really old LCD won't take it. RGB nocked up and I get a very...

Non-corrosive desoldering flux can be very helpful at making sure oxidised solder melts and flows without excess heat application Use proper lead low temperature solder whenever you have to resolder after a non-clean suck Never pull until free but gentle twisting can often break the join between...

Oh yes :)

It inverts reset so when the PET gets a reset, the interface clear line is pulled and all devices no matter what they are doing immediately let go of the line and await further commands (if they follow the IEEE-488 spec).

I imagine the pin connected to nowhere is so you can store the jumper from red to ? when not in use.

With a RISC OS machine, have you tried holding down delete when powering it up ? It will reset the video to mode 0 15kHz.

Corrections are all updated on Github but they were. IC 43 pins 10,13 & 14 - connect to adjacent rail - fixed IC 39 pin 14 - connect to adjacent rail - fixed IC 23 pin 10 - connect to adjacent rail - fixed IC 33 pin 10 - connect to adjacent rail - fixed Cosmetics R11 should read 30K Two R23's...

Just a note to point out I still have two sets of boards available if anyone wants them They would need the minor errors found correcting and they are not ENIG plated and dont have hard gold fingers but as has now been shown, they do work ! (Mr Null, what a hero in taking on the challenge) I...

Must be nice to have so much space ! :)

and iiiiiiiiii have become comfortably numb... epic. Good choice.

Oddly, I had already changed it to 7408 even though I put 7403 in the post.