The Sinclair QL Forum

The fact the 8049 can control both interrupt lines seems to be a hangover from the development days - interrupt level 7 (NMI) is basically set by pressing CTRL ALT 7 on the QL keyboard - this triggers code in the 8049 for it to reset itself and at the same time trigger the NMI on the QL - the usual ...

I remember seeing output like that with Aurora card and qubide where my qubide card had a bridge between 2 address lines, causing a short on the bus. The regular repeating black lines are a giveaway. I would check the adjacent address lines and see if you have a solder bridge somewhere, could be a ...

That is impressive!

X axis looks ok for a 7.5MHz, given that signal is repeating roughly 2/3 of the scale interval

In the message in the Wanted Section:



As for the ULA, I don't know if anyone has reverse engineered that one. It's probably quite simple.


As part of my Service Manual update, I was looking at the Microdrive, giving a more detailed description of the Microdrive circuitry Headboard and ...

The service manual mod list is here:

https://www.sinclairql.net/srv/qlsm4.html#s4c

I replaced that keyboard connector on a couple of QL's with a JST connector - it just makes life easier if you have to get inside the machne...

That's good news - looking forward to seeing this!

I am working on a 3 chip design - a couple of TTL chips and a 28 pin PIC that will fit in the 40 pin footprint of the IPC chip.

By way of a teaser - these are the goals of the replacement:

Compatible with all HERMES and most of the SuperHemes extensions.
Interrupt driven sound that doesn't affect ...

The modification introduces a small amout of negative bias (-12v through 100K resistors) to the RAW inputs on the ZX8302. It is supposed to help with conditioning the signal from the Microdrive units.

It's one of a number of 'required modifications' that are listed in the service manual

This is the contact cleaner I've used in the past:

https://amzn.eu/d/bg8tnaa

Like I say - not cheap - but it's effective - Search for Deoxit. I am sure there are other capable brands too - I found that one first after a recommenation from a guitar playing friend.