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by rubber_jonnie
Sat Feb 03, 2024 3:55 pm
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

That looks like a signal to me, however, just as with the ZX81 there's no backporch so a colour TV (and modern LCDs) will not work with it. Analogue colour TVs will have a very dark picture and modern LCDs will just see nothing at all. You'll need a mono-CRT for it to work unless you can find somet...
by rubber_jonnie
Sat Feb 03, 2024 3:10 pm
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

So not much time to sit down with the 600 today, as I have a few other things to do, but I went back and rechecked the CPU clocks which are still all good, though I will fit the correct value 150pF cap when it comes. It seems that the video signal does now mix with the sync, but I'm not convinced I'...
by rubber_jonnie
Sat Feb 03, 2024 10:05 am
Forum: MEMBER BLOGS
Topic: General Stuff(tm)
Replies: 1699
Views: 322831

Re: General Stuff(tm)

Got back to Oxford yesterday evening. Having brought one of the Keypros home, the one with the explodified RIFA, I had another look. I replaced the exploded and the other three RIFAs and gave the PSU a test... nothing. Looks like the exploding RIFA took something else out. It's not the fuses as I'm...
by rubber_jonnie
Fri Feb 02, 2024 10:11 pm
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

stephen_usher wrote: Fri Feb 02, 2024 7:08 pm So, effectively you had a low pass filter on your clock! :-)

Glad you now have a clock anyway. Do you get any output now?
Bloody annoying but at least I found it

No output yet but not had a chance to look further tonight. At least the clocks are good I can start to troubleshoot the rest.
by rubber_jonnie
Fri Feb 02, 2024 4:28 pm
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

Oh.Boy> ARRRRRGGGGGGHHHHHH. So I lifted one leg on C65 and guess what? The clock only started working as it should, and it turns out that it should have been a 150pF not a 150nF capacitor!!! I'm not sure if it was my blunder, but I don't care because now I have good clocks I can trace the clock roun...
by rubber_jonnie
Fri Feb 02, 2024 2:31 pm
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

Well, this is the gift that keeps on giving... I installed the 8MHz xtal and get a good 8Mhz signal at U79, pin 5. So I bridge the socket to allow U29, the LS93, to pickup that signal on pin 1, which it does just fine. OK, so over to pin 11 where I'm expecting to see 1MHz, but I don't, and pin 12 wh...
by rubber_jonnie
Fri Feb 02, 2024 1:56 pm
Forum: ROM UPGRADES
Topic: MegaST ROM adapter - black screen
Replies: 33
Views: 1377

Re: MegaST ROM adapter - black screen

OK, so looking at the bottom I can see two solder joints that don't look right, shown by the arrows: st-005_RJ.jpg The top one looks like it has bridged across to ground, and the bottom looks like it is a cold or incomplete joint. I'd still suggest that you need to change the jumper header to a squa...
by rubber_jonnie
Fri Feb 02, 2024 11:56 am
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

I do hope that the 8MHz crystal and the simpler circuit fixes things. From the look of the output on your telly it seems that there are things trying to be displayed. Me too. Surely by dispensing with the clock doubling trickery we can get 8MHz straight to the LS93. It certainly does try to display...
by rubber_jonnie
Fri Feb 02, 2024 11:14 am
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

Oh well. Shows that it wasn't the voltage level then. Definitely worth a try. I also pulled the sockets for the LS00 and LS86 to see if there were any shorts below, but nothing there. It's just that LS86 that gives zero output on pin 6. Pin 5 has input no problem, and I have double checked that pin...
by rubber_jonnie
Fri Feb 02, 2024 9:01 am
Forum: 8 BIT CORNER
Topic: OSI 600D Superboard Build
Replies: 314
Views: 55184

Re: OSI 600D Superboard Build

stephen_usher wrote: Thu Feb 01, 2024 9:58 pm Did you get a chance to test this?
Tested this morning, made no difference.

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