Search found 567 matches

by 1024MAK
Tue Oct 22, 2013 2:56 pm
Forum: Hardware
Topic: Miracle Systems Floppy PSU
Replies: 25
Views: 8332

Re: Miracle Systems Floppy PSU

Yes, if the drives only need +5V, the 7805 will supply them. This was my first thought, that the drives are single supply models. However, when I searched for information on them, I found a picture showing the model number and also showing the power requirements, which stated +5V and +12V. So it loo...
by 1024MAK
Tue Oct 22, 2013 8:40 am
Forum: For Sale
Topic: Sinclair QL Floppy Disk Interfaces
Replies: 47
Views: 13788

Re: Sinclair QL Floppy Disk Interfaces

Mark, what do you mean? Why SRAM? Or, what do you mean, "modern" DRAM? As in... DDR perhaps? I mean use one (or maybe two) 512k x 8 bit SRAM chips instead of the DRAM chips used on a Gold card (for example) so that the QL has more than it's standard 128k RAM. I'm not sure where the price ...
by 1024MAK
Mon Oct 21, 2013 11:44 pm
Forum: Hardware
Topic: Miracle Systems Floppy PSU
Replies: 25
Views: 8332

Re: Miracle Systems Floppy PSU

Yikes! Transformer, rectifier bridge, shitty capacitors, 7812, no filtering? Looks more like the rectified 9V ac from the transformer is smoothed by the large blue electrolytic capacitor, this the feeds the +12V dc supply to the FDD (but off load will be about 13V). Meanwhile this supply also feeds...
by 1024MAK
Mon Oct 21, 2013 11:33 pm
Forum: Hardware
Topic: Miracle Systems Floppy PSU
Replies: 25
Views: 8332

Re: Miracle Systems Floppy PSU

Looks fixable to me :mrgreen: (normal get out clause may apply :P ) With the unit unplugged you are looking to see low resistance readings (from zero ohms to about 10 ohms max) across the fuse, the primary windings and the secondary windings. Check to see if the board has been coated in a protective...
by 1024MAK
Mon Oct 21, 2013 9:24 pm
Forum: For Sale
Topic: Sinclair QL Floppy Disk Interfaces
Replies: 47
Views: 13788

Re: Sinclair QL Floppy Disk Interfaces

:arrow: And (*drum roll please*), tenthly, would we want SRAM chips instead of (I presume) fast page DRAM (can't be bothered to go and check at the moment) OR we would need some err, modern DRAM modules (with their own "new to us" access timing)... :P

Mark
by 1024MAK
Mon Oct 21, 2013 9:15 pm
Forum: Hardware
Topic: QL-SD card project
Replies: 43
Views: 16405

Re: QL-SD card project

Thinking about my comments after hitting the post button, if the 'scope is grounded at a good "solid" ground point, probably not ground bounce :oops:

Mark
by 1024MAK
Mon Oct 21, 2013 9:06 pm
Forum: Hardware
Topic: QL-SD card project
Replies: 43
Views: 16405

Re: QL-SD card project

Yes, with digital signals, correct timing is everything. A question. Could some of the problems be due to a poor ground layout / tracks? Are you seeing a form of "ground bounce" where the voltage drop through the ground is helping to cause the voltage on the signal lines to be out of spec?...
by 1024MAK
Mon Oct 21, 2013 8:03 pm
Forum: Hardware
Topic: QL-SD card project
Replies: 43
Views: 16405

Re: QL-SD card project

Best get some 220Ω resistors and 47pF capacitors then to low pass the filtor the signal...
Follow that with a schmitt trigger input and plug and pray :P

Yes, I know, it's never that simple :-(

Mark
by 1024MAK
Mon Oct 21, 2013 7:14 pm
Forum: For Sale
Topic: SOLD 2 x Small QL Interfaces
Replies: 4
Views: 1675

Re: 2 x Small QL Interfaces

Curiosity has won, If these are both still available, could you add them to my ever growing order please Rich :P

Mark
by 1024MAK
Mon Oct 21, 2013 5:33 pm
Forum: The Welcome Area
Topic: Hello from Yorkshire
Replies: 5
Views: 2930

Re: Hello from Yorkshire

Welcome Bob!

:D :D :D

Mark