OSI 600D Superboard Build

Any 8bit repairs, images, cool things, upgrades etc.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10944
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: OSI 600D Superboard Build

Post by rubber_jonnie »

OK, so C6 replaced with the correct value but no difference.

I also pulled U62 in case that was bad, It wasn't, and also tried with one leg of C6 lifted, but still no output on Pin 6, so replacement CA3130's are ordered.

Provided I then get output from that I can then start to chase down where the output gets to and if R57 works to adjust the input as expected.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10944
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: OSI 600D Superboard Build

Post by rubber_jonnie »

So I think my CA3130 was a fake, here are the new ones on the left, old one on the right:

IMG20240425104130.jpg
IMG20240425104130.jpg (181.02 KiB) Viewed 8871 times

All 3 of the new ones work just fine, and I get a nice signal where I should at pin 6 of and over at pin 5 of U69:

IMG20240425115252.jpg
IMG20240425115252.jpg (263.77 KiB) Viewed 8871 times

The blue trace is at the tape in currently coming from the aux out whilst I do a save, and the yellow trace is pin 5 of U69. The pulse width at U69 is within the range of 500uS to 630uS according to the service manual after adjusting R57.

I am able to save however I don't know if saving is working 100% as I could have cassette and tape player issues, so whilst I get what sounds good when I save, when I try to load it back in it's garbled. Nearly there though and I can test with another cassette deck.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
User avatar
stephen_usher
Posts: 5900
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: OSI 600D Superboard Build

Post by stephen_usher »

I wonder what chip the original was. Maybe a 555 timer.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10944
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: OSI 600D Superboard Build

Post by rubber_jonnie »

stephen_usher wrote: Thu Apr 25, 2024 3:06 pm I wonder what chip the original was. Maybe a 555 timer.
Wouldn't surprise me.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10944
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: OSI 600D Superboard Build

Post by rubber_jonnie »

OK, so I have made some progress thanks to help over at osiweb.org.

I was given a small basic routine as follows:

10 SAVE
20 POKE 61440, 21
30 PRINT "U";
40 POKE 14,0
50 GOTO 30.

What this odd little routine does is similar to the test from the service manual, but it causes a 150Hz signal to be sent from the 6850.

Then by jumpering from pin 9 of the expansion connector to pin 10, this 'save' signal then gets routed straight into the cassette in port, and it can be followed all the way through back to the 6850.

What I ended up having to do was swap U62, U63 and U69 for various different makes, and I finally found a combination that gave me this:

IMG20240610223507.jpg
IMG20240610223507.jpg (201.76 KiB) Viewed 168 times

The yellow trace is the output from the 6850 and the blue trace is the input into the 6850. The shift is normal according to the folks over at osiweb.

I'm now getting partial loads and things are starting to almost work and I'm fairly confident that the save part is good as I am almost able to load a complete program from tape that I saved previously.

All of the ICs I removed and swapped about seem to be working just fine according to the TL866, but clearly there are more timing issues between different ICs that mean finding a 'set' that works well together is trial and error.

Progress at least though.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Post Reply

Return to “8 BIT CORNER”