Search found 727 matches

by Cristian
Tue Apr 28, 2020 8:39 am
Forum: Hardware
Topic: KryoFlux USB floppy controller
Replies: 16
Views: 941

Re: KryoFlux USB floppy controller

the first an unbranded Chinese one just vaguely marked "FD-05PUB" Mine looks identical, except for the model number: US-FDD I use it with WindowsXP and can handle/format both 720K and 1.44MB disks. I know someone who utilize it with Windows10 and it works. Ralfr, have you tried also with ...
by Cristian
Sat Apr 25, 2020 12:52 pm
Forum: Hardware
Topic: KryoFlux USB floppy controller
Replies: 16
Views: 941

Re: KryoFlux USB floppy controller

I have bought a new one, Freecom branded, this has the same 3,5 floppy from Mitsumi UFDD 061M inside, but does not work with DD disks Probably several USB drives are limited to 1,44MB. A matter of firmware? I don't know. I suppose the best way is to ask always the seller about the format details, w...
by Cristian
Fri Apr 24, 2020 7:05 pm
Forum: Hardware
Topic: All RAM chips destroyed??
Replies: 95
Views: 14381

Re: All RAM chips destroyed??

check this pin on the ZX8302 chip to 5v and GND and see if there is any short circuit there. This is Pin 2 on the chip. There is a resistor between this pin and 5V line - value is 3.3K, so there should be some resistance when measuring to 5V. Updates about repair status. - Cheched resistance value ...
by Cristian
Fri Apr 24, 2020 8:48 am
Forum: Hardware
Topic: All RAM chips destroyed??
Replies: 95
Views: 14381

Re: All RAM chips destroyed??

First of all, thank you very much Pr0f and Tobias for your important suggestions. Unfortunately I have no access to oscilloscopes, so for the moment I can not test the trimming capacitor. Regarding the expansion port, the pins look perfect. The start-up and memory test looks severely slowed down to ...
by Cristian
Thu Apr 23, 2020 10:54 am
Forum: Hardware
Topic: All RAM chips destroyed??
Replies: 95
Views: 14381

Re: All RAM chips destroyed??

Just tested also IC23 (ZX8302). When connected to other working machines, all seems OK. I've updated the summarizing picture in my previous post. I still get random results at power on (mostly garbage patterns, usually vaguely regular). Sometimes QL tries slowly a real startup, as shown in the video...
by Cristian
Wed Apr 22, 2020 2:59 pm
Forum: Hardware
Topic: All RAM chips destroyed??
Replies: 95
Views: 14381

Re: All RAM chips destroyed? - Repair progress

--Repair progress update-- I made all the "mandatory modifications" (for Issue5 board) as per Service Manual. There might be some little improvement in the startup sequence (or probably it's my imagination), but the substance remain the same. The machine sometimes try to start, wit the the...
by Cristian
Wed Apr 22, 2020 1:42 pm
Forum: Hardware
Topic: The Mandatory Modifications
Replies: 7
Views: 2036

Re: The Mandatory Modifications

I wish to learn from your steps, if you shared here in the forum So I had the time to apply all the mandatory modifications to my ISS.5 QL. The first 2 mods had already been done (by Sinclair?) so, here is what I've done: - cut a track near the heatsink, at the border of the board and added resisto...
by Cristian
Tue Apr 21, 2020 9:58 am
Forum: Hardware
Topic: 5.25" floppy drive configuration
Replies: 27
Views: 1130

Re: 5.25" floppy drive configuration

some 1.2 MB drives have switch to 300 RPM for compatibility purposes. Thanks, this information is interesting. Actually there are some 1.2MB drives with the 300 RPM switch or jumper. Unfortunately the M2553K-83B does not have it. I couldn't find a specific datasheet and, for what I can see, there i...
by Cristian
Sun Apr 19, 2020 5:42 pm
Forum: Hardware
Topic: 5.25" floppy drive configuration
Replies: 27
Views: 1130

Re: 5.25" floppy drive configuration

Same as on SCSI. Remove on the thru device, keep them in place on the last device. Thank you Dex for your explanation. So in conclusion, I made dozens and dozens of tests with and without terminations, non-twisted and twisted cables, all possible format variations and media types, Trumpcard and Gol...
by Cristian
Sat Apr 18, 2020 2:35 pm
Forum: Hardware
Topic: 5.25" floppy drive configuration
Replies: 27
Views: 1130

Re: 5.25" floppy drive configuration

Oh, sorry. I misunderstood Derek's reply. Thank you for your clarification.
Still, I don't know what should I do with these termination resistors...