Search found 568 matches

by martyn_hill
Fri Jun 26, 2020 5:00 pm
Forum: Hardware
Topic: Issue 6 VM12 & resistors confusion
Replies: 79
Views: 3180

Re: Issue 6 VM12 & resistors confusion

Hi Ruptor I don't recall if you ever checked/replaced the ZX8302 - bear in mind that any comms with the IPC (and this the keyboard) must flow through the 8302 first. One clue, when using Minerva, is whether you get a consistent 'time/date' shown after repeated pressing of Reset - it'll be a nonsense...
by martyn_hill
Wed Jun 10, 2020 12:34 am
Forum: Hardware
Topic: Boot Q68 without monitor and keyboard
Replies: 21
Views: 806

Re: Boot Q68 without monitor and keyboard

As far as I recall, the Q68 start-up code will complain and stall if a mouse is plugged in to the KB port (i.e. in to the wrong socket in the splitter), so you are stuck with needing a KB...

Perhaps Peter G will know of a work-around?
by martyn_hill
Tue Jun 09, 2020 9:03 pm
Forum: Hardware
Topic: Boot Q68 without monitor and keyboard
Replies: 21
Views: 806

Re: Boot Q68 without monitor and keyboard

Hi afx

I believe that the PS/2 KB must be present to allow the Q68 to boot, but no monitor need be attached.
by martyn_hill
Sun Jun 07, 2020 10:43 pm
Forum: Hardware
Topic: zx microdrive on ql for testing the zx drive
Replies: 7
Views: 288

Re: zx microdrive on ql for testing the zx drive

Hi techy Regarding the IF-1, as well as a defective ULA, it is also quite possible that the Spectrum's z80 CPU is (slightly) defective. The IF-1, along with certain other Spectrum peripherals rely on a working 'M1' (Machine-cycle-1) signal from the CPU, active during the instruction-fetch cycle. An ...
by martyn_hill
Fri Jun 05, 2020 6:34 pm
Forum: Hardware
Topic: Micro drive continuously spinning
Replies: 21
Views: 729

Re: Micro drive continuously spinning

Hi again Gary So to fix the duff MDrive, will it be a case of replacing its ULA? Whilst the cause of this MDV failure is likely to be the ULA, I wouldn't neccessarily recommend trying the replacement yourself. Much easier to find an entire MDV replacement, that come up from time to time. You might w...
by martyn_hill
Fri Jun 05, 2020 4:22 pm
Forum: Hardware
Topic: Micro drive continuously spinning
Replies: 21
Views: 729

Re: Micro drive continuously spinning

Hi Gary That is good news! Given the shared nature of the MDV bus, one flaky drive can be expected to interfere with another, otherwise good unit, so your latest results make sense. Just for interest, we could infer from your results the following potential situation: 1. The ULA of (originally) MDV#...
by martyn_hill
Thu Jun 04, 2020 6:06 pm
Forum: Hardware
Topic: Micro drive continuously spinning
Replies: 21
Views: 729

Re: Micro drive continuously spinning

Hi Gary The ULA in question is soldered direct to the 'head-board' of each MDV unit. The units come complete, with head-board semi-permanently fixed to the chassis - whole units do come up for re-sale from time to time - condition varies, however. Given that both units spin continuously, I suspect b...
by martyn_hill
Thu Jun 04, 2020 3:17 pm
Forum: Hardware
Topic: Micro drive continuously spinning
Replies: 21
Views: 729

Re: Micro drive continuously spinning

Hi Gary and welcome! You'll find quite a few posts relating to flaky MDVs around here, each with diverse recommendations depending upon the specific symptoms, but I'll start by saying that, in my experience, constantly spinning drives is indicative of faulty MDV ULAs which are less than convenient t...
by martyn_hill
Mon Jun 01, 2020 10:41 pm
Forum: For Sale
Topic: Free working QL and broken 512k RAM expander
Replies: 8
Views: 512

Re: Free working QL and broken 512k RAM expander

Hi Scot!

I'm due a visit to my brother in Weston-SM over the next month or so - so if you haven't found a taker by then, please keep me in mind :-)
by martyn_hill
Sun May 31, 2020 7:09 pm
Forum: Hardware
Topic: Issue 6 VM12 & resistors confusion
Replies: 79
Views: 3180

Re: Issue 6 VM12 & resistors confusion

Hi Ruptor That's disappointing, but as you say, only one of the potential causes of what you have observed. Pulling up made little difference but pulling down caused the memory test to put FFFFFFFF out and read back FEFEFEFE every time which I thought was strange. Why is the output word fixed if it ...