This makes more sense now on the switch side of things. The switch enable will trigger that lower of the 3 comparator's (there are 4 in the 339 package), and that in turn will switch Q6 on, allowing the SW pin to rise towards +12V, it would normally be dragged to 0.6V by the bias resistor to -12V a...

Thank you 1024MAK and Pr0f, your answers are definitely and better justified than anything I heard so far! The only remaining mystery is the fact that the switch circuit make sense only if the SW pin has a positive supply even though I have measured a negative voltage. Here is some description of th...

One quick question - as this could be a showstopper for your project... What monitor or TV do you intend to use? Light pen will only work correctly with a CRT based TV or Monitor, as the LCD doesn't have a 'light spot'. Well, not only it needs a CRT monitor, but it needs the specific high resolutio...

Hi, I want to recreate the electronic inside a sophisticated light pen for a vintage computer. Nothing related to the QL hence the "Off-Topic" section. I have the original blue print of the electrical schematic. However, there are two or three things that can be interpreted one way or the ...

What happens when you swap the QLs between the two sets of expansions? Does the problem stay with the respective Gold Cards, or does it stay with the respective QLs? It would be difficult for me to test this because the SCG was modified to work with a backplane (I don't remember what modification I...

For me this looks like a bad contact somewhere (memory ?). I had a similar problem, it went away when I moved the SGC DRAM chips a little inside their sockets. Hi, Thank you all for your answers. Based on your experiences, I carefully removed all RAM chips from the SuperGoldCard, I inspected them a...

Hi, I currently have 3 QL systems, 1 Q68, 1 SGC + Aurora and 1 original QL + GC. The Q68 works perfectly :-) However, the other two are giving me troubles but only when booting: The Gold Card System problem is the following: When I power up the computer, it boots as it should i.e. first memory test ...

Ok thanks!

(Got the ZXzine too!)

Francois

Just discovered your magazine. Very nice. How do I get the first 4 issues ??

Hi Dave,

I have a Minerva mk2 on my goldcard QL and have been using the I2C on a couple of projects. So if you have any question, let me know.

François