The Sinclair QL Forum

You'll only need a 250mA or 500mA 7805 - a 1 or 1.5A 7805 is overkill and will just make a lot of heat. On this 500mA 7805 in SuperRAM I have used 2x .1uF ceramic and 2x 20uF 16V electrolytic, one each input to ground and output to ground. I also placed a 0.1uF ceramic at each IC, as close to the +...

Of course, there are a number of tricks to slow down a fast switching signal... Using series resistors is the most common method. But as was said before, the 7.5 MHz QL is not fast, so the slower GAL chips are fine. Oh, and what we are really talking about here, with "fast edges" is slew r...

Is that what is called mass storage?

Mark

Also the schematic for the Miracle Expanderam 512K does not use the FC2,FC1,FC0 signals.
Schematic available from http://www.dilwyn.me.uk/docs/hardware/QLperip.zip file name "expram_sch.pdf".

Mark

Is decoding of the FC2,FC1,FC0 signals really required in a QL. After all, to a 68000 series CPU, a QL is a simple device?

Mark

I need to fit +5V voltage regulator since expansion connector provides +9V. I hope it won't need extra heat sink and it won't overheat inside QL. Using the +9V supply will not overheat the QL, as this is the supply that comes from the external PSU. For the relatively simple job that the GAL is doin...

That's the second person with a QL that had a bad 74LS257 chip to post on this forum in the last 12 months.

Well done Phill on getting it going

Mark

Sounds interesting...

Mark

If you have a Gold card or SGC, it is worthwhile seeing if the system will run with it plugged in, as then you can tell if it is a DRAM cell or internal DRAM decode fault. Also keep in mind some modes of failure of the multiplexers 74LS257 (IC19 & 20) or 74LS245 (IC21) bi-directional buffer can ...

Don't worry Dave. It's now time for me to put an order in on your site :mrgreen: BTW, if you have enough of those DIN "edge"-connectors, I'm after one. Somewhat off-topic: Funny that during the night, I have just been swapping (changing) industrial 68000 CPU system cards due to life expire...