Search found 28 matches

by hjalfi
Mon Nov 25, 2019 8:17 pm
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

If you're new to soldering, I'd definitely recommend practicing on something other than the Spectrum first. It's pretty easy to work on, with huge joints and tracks the size of your thumb, but Sinclair definitely skimped on the materials and the board does have a bit of tendency to fall apart while ...
by hjalfi
Sun Nov 24, 2019 11:46 pm
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

The drop-in switch mode regulator has worked like a dream for me --- no heat sink, no heat, no problems. Strongly recommended!
by hjalfi
Fri Aug 24, 2018 7:30 pm
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

I really like it when I find a problem that turns out to be caused by me doing something really dumb --- because it's usually very easy to fix. Turns out the Spectrum was just poorly calibrated, and five seconds' work with a screwdriver fixed it. It looks really nice on my Trinitron PVM monitor, and...
by hjalfi
Thu Aug 23, 2018 6:15 am
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

It does PAL and SECAM, with a switch. It also has lights to let you know whether it detects colour. Interestingly, if I route the video through an CV-to-HDMI-to-CV cover I get nice vibrant colour and the PAL light lights up. Connected directly I get mono and no light. This suggests that the monitor'...
by hjalfi
Wed Aug 22, 2018 9:46 pm
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

My nice new Sony PVM has arrived! The Spectrum displays in mono on it. It displays in colour on two out of my three composite-capable LCDs (the third is a big-screen TV and just shows black). I was kinda expecting a real CRT to do better than a modern LCD. Is this behaviour symptomatic of anything? ...
by hjalfi
Sat Aug 04, 2018 10:23 pm
Forum: Programming
Topic: ZX81 basic: running the program without clearing variables
Replies: 7
Views: 922

Re: ZX81 basic: running the program without clearing variables

I don't think 'pedestrian' is the right word --- that implies it's somehow ordinary, which ZX81 Basic is anything but. I think my favourite combination of features are the absence of multiple statements per line and the missing ELSE clause in if statements: these synergise beautifully for maximum in...
by hjalfi
Sat Aug 04, 2018 3:04 pm
Forum: Programming
Topic: ZX81 basic: running the program without clearing variables
Replies: 7
Views: 922

Re: ZX81 basic: running the program without clearing variables

Oh, yeah, I completely forgot you could do that! Except it didn't save the GOSUB stack along with the program state, hence the warning in the manual... Gosh, I'd forgotten how... opinionated... ZX81 Basic is. Also slow. Incidentally, several of the programs in that issue of _Sinclair Programs_ are i...
by hjalfi
Fri Aug 03, 2018 7:18 pm
Forum: Programming
Topic: ZX81 basic: running the program without clearing variables
Replies: 7
Views: 922

ZX81 basic: running the program without clearing variables

So ZX81 Basic, unusually, allows modification of the program without clearing all the variables; and SAVE and LOAD will save them and reload them. Except, RUN implicitly does a CLEAR, wiping them before the program runs. Given that the ZX81 does (AFAIK) allow autorunning of programs, how does this m...
by hjalfi
Sun Jul 29, 2018 5:19 pm
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

Or maybe, and bear with me, I know this is a long shot... maybe I could just connect the composite decoupling capacitor the right way round? Okay, so I also added the transistor mod, so maybe that made a difference too, but all the monitors I've tried this with are quite happy now. (Although the ins...
by hjalfi
Fri Jul 27, 2018 11:59 am
Forum: Hardware
Topic: Brand new r2 48kB, not quite working
Replies: 53
Views: 4688

Re: Brand new r2 48kB, not quite working

Thanks for the links; all useful. The transistor mod is simple enough I may just try it, and see what happens --- it can't make things worse. It's still really weird that there's no sign in the scope of anything wrong. The timing looks fine (64us per scanline). The voltages look fine (1V from the bo...