The Sinclair QL Forum

Issue 5 or 6 component diagrams as well as the circuit configuration has components labelled DC8 etc. it refers to a capacitor that appears non-polarised, and as far as memory from my electronic days is able to determine, I cannot reason what or why it is referring to. A DC designation is strange as all other capacitors have the expected C, can anyone enlighten me?

While I am at it, the circuit diagrams also have a peculiar orientated labelling system across some components, namely FT and BK. This refers to measurements I think, as the Service Manual refers to them such as:

FUNCTION CIRCUIT REF WAVEFORM/VOLTAGE
± 12 V voltage regulator input + side of D26 15.6 V a.c. ± 2.0 V
+ 5 V voltage regulator input + side of C41 + 9.0 V a.c. ± 2.0 V
+ 12 V voltage regulator output FT side of C38 + 12.0 V d.c. ± 0.25 V (no discernible ripple)
+ 5 V voltage regulator output FT side of C42 + 5.0 V ± 0.15 V (no discernible ripple)

However I cannot seem to find out the DC thing, and its bugging me.

Okay, not having a QL schematic diagram in front of me, but going on typical use in the electronics industry...
Capacitors labeled as DC are likely to be capacitors used to decouple the power supply tracks/traces, hence DC for decoupling capacitor.
FT is likely to mean front,
BK and is likely to mean back.

Hope this helps

Mark

Hi,

I have the official QL Service Manual, I was always going to reproduce the QL Schematics in Eagle, but never got around to this. As the layouts are already done. Do you think this might be a good idea.

In the 1990s I did a modular QL design on paper, which was mainly splitting the QL circuit board in to 3 modules: CPU, I/O, Ram boards connected by a central bus. But then the Aurora came out and this was abandoned. I might that a revisit to this, since I have more time and the CAD tools are better.

Interesting.

There are a couple of horrible mistakes in the schematics in the reference guide - so I've heard.

I have designed about 2/3rds of a replacement QL mainboard that is 100% faithful to the original layout of an Iss. 6 board but with better power/ground provision, and mostly in SMD. I got stuck on the errors.

If there were an Eagle schematic, it would be so much easier!

I also like the idea of splitting the QL across small PCBs to create something similar to an S100 buss microcomputer system - though the QL version could be tremendously more powerful and flexible if the backplane just happened to be the one we know and "love." It also means people could release incremental improvements to the CPU/IO or memory, without having to design a whole new computer.

Hi,

My basic idea was to split the QL into the major parts that could be upgraded at a later date... but hang on that sounds like the IBM theory for PCs.

This would result in targeted work on a 68060 addon card, more memory, enhanced video, proper I/O facilities, multiple channel sound.

Probably S100 bus interfacing was the correct interface, but I never got that far.

Since I am no working and can think of QL things all day, this could be good to keep the little grey cells working.

Derek_Stewart wrote:I have the official QL Service Manual, I was always going to reproduce the QL Schematics in Eagle, but never got around to this. As the layouts are already done. Do you think this might be a good idea.

If you have the time, I would love to have a good quality BBQL schematic

At the moment, I use extracts of a PDF (of the service manual) and sometimes clean bits of the image up while comparing them to the slightly poorer quality scanned schematics that are available on the web (the images in the service manual rubbish, but are slightly better quality than the available scanned schematics).

Mark

I use the redrawn circuit diagrams that are available as PDF files, they are dated Feb 2014.

I think I got them from here but maybe not, I can upload them if anyone is interested.

Cheers.

Phill.

Hi Phil,

My Service manual details QL Boards Issue 5 & 6

I was going to reproduce the schematics, as an exercise in CAD drawing for myself. I would like to see what you have done already.

There are errors in the QL Service Manual, which I think Tony Firshman, did a summary of the errors, but I can not find this. I will ask him if he still has the files and post them here.

At the end of the day, I think we need a concise schematic for each QL board issue.

Still the QL board is only double sided and no inner layers, this able to be done with a little time.

Derek_Stewart wrote:Hi Phil,

Phill <<

My Service manual details QL Boards Issue 5 & 6

I was going to reproduce the schematics, as an exercise in CAD drawing for myself. I would like to see what you have done already.

I didn't do them I forgot where they came from originally, it may have been here or the Yahoo QL group.

Still the QL board is only double sided and no inner layers, this able to be done with a little time.

Yes I have done this for a couple of Spectrum and Acorn addons over the years, only being double sided deffo helps.

Anyway here's the circuits I have : Cheers.

Phill.

prime wrote:I use the redrawn circuit diagrams that are available as PDF files, they are dated Feb 2014.

I think I got them from here but maybe not, I can upload them if anyone is interested.

Cheers.

Phill.

I think they are possibly the same as the ones available on my website at http://www.dilwyn.me.uk/docs/hardware/index.html.

On that page, they're in the section entitled 'QL Circuit Diagram'. There's also a short text file with explanation of differences to the Service Manual diagrams.