Search found 592 matches
- Thu Apr 10, 2014 12:23 am
- Forum: Hardware
- Topic: Internal ram upgrade to 640k - continued
- Replies: 38
- Views: 21965
Re: Internal ram upgrade to 640k - continued
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 +...
- Mon Apr 07, 2014 11:49 am
- Forum: Hardware
- Topic: Internal ram upgrade to 640k - continued
- Replies: 38
- Views: 21965
Re: Internal ram upgrade to 640k - continued
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...
- Sun Apr 06, 2014 11:51 pm
- Forum: For Sale
- Topic: Load of Microdrive Cartridges on ebay
- Replies: 6
- Views: 3837
Re: Load of Microdrive Cartridges on ebay
Is that what is called mass storage?
Mark
Mark
- Sun Apr 06, 2014 11:30 pm
- Forum: Hardware
- Topic: Internal ram upgrade to 640k - continued
- Replies: 38
- Views: 21965
Re: Internal ram upgrade to 640k - continued
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
Schematic available from http://www.dilwyn.me.uk/docs/hardware/QLperip.zip file name "expram_sch.pdf".
Mark
- Sun Apr 06, 2014 10:39 pm
- Forum: Hardware
- Topic: Internal ram upgrade to 640k - continued
- Replies: 38
- Views: 21965
Re: Internal ram upgrade to 640k - continued
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
Mark
- Sun Apr 06, 2014 10:34 pm
- Forum: Hardware
- Topic: Internal ram upgrade to 640k - continued
- Replies: 38
- Views: 21965
Re: Internal ram upgrade to 640k - continued
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...
- Sun Apr 06, 2014 1:09 am
- Forum: Hardware
- Topic: Faulty machine.
- Replies: 8
- Views: 4143
Re: Faulty machine.
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
Well done Phill on getting it going
Mark
- Thu Apr 03, 2014 4:51 pm
- Forum: Hardware
- Topic: DIY - QL style keyboard with mechanical Cherry keys ?
- Replies: 8
- Views: 7867
Re: DIY - QL style keyboard with mechanical Cherry keys ?
Sounds interesting...
Mark
Mark
- Thu Apr 03, 2014 2:40 pm
- Forum: Hardware
- Topic: Faulty machine.
- Replies: 8
- Views: 4143
Re: Faulty machine.
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 ...
- Thu Apr 03, 2014 7:49 am
- Forum: General QL Chat
- Topic: The humongous Sandy Electronics thread...
- Replies: 178
- Views: 71594
Re: The humongous Sandy Electronics thread...
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...