General Stuff(tm)

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stephen_usher
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Re: General Stuff(tm)

Post by stephen_usher » Thu Oct 14, 2021 12:01 am

Yes, this is on the cart and it works in an ST.

The clock rate on the TT is fixed at 32MHz.
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.

stephen_usher
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Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
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Re: General Stuff(tm)

Post by stephen_usher » Thu Oct 14, 2021 10:03 am

Thinking about this overnight I may try resistors first, just put one 10K on one pin and see what happens. The cartridge was messed about with as an experiment by Gadgets by Small before they sold it so I may as well keep up the tradition.

But before any hardware hacking I'll replace the ROMs with a matched pair of 27C512s, both rev.C versions and see what happens. It could be the mixed rev.B and rev.C ROMs have changes which don't affect Spectre on and ST but do on an TT.
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.

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Steve
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Joined: Fri Sep 15, 2017 11:49 am

Re: General Stuff(tm)

Post by Steve » Thu Oct 14, 2021 10:22 am

I just read your post about the retro computer festival..! Where and when was it? I completely had no idea, I would have loved to have gone!! Where should I look out in future to know of such events? Thx

stephen_usher
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Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
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Re: General Stuff(tm)

Post by stephen_usher » Thu Oct 14, 2021 10:44 am

Steve wrote:
Thu Oct 14, 2021 10:22 am
I just read your post about the retro computer festival..! Where and when was it? I completely had no idea, I would have loved to have gone!! Where should I look out in future to know of such events? Thx
It was last weekend at the Museum of the History of Computing in Cambridge.

This may be of some help: http://www.computinghistory.org.uk/det/ ... h-october/
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.

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rubber_jonnie
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Re: General Stuff(tm)

Post by rubber_jonnie » Thu Oct 14, 2021 11:20 am

Steve wrote:
Thu Oct 14, 2021 10:22 am
I just read your post about the retro computer festival..! Where and when was it? I completely had no idea, I would have loved to have gone!! Where should I look out in future to know of such events? Thx
The Centre for Computing History is a great little place, I've been to quite a few events there and have enjoyed them thoroughly. As my birthday is in October and because they often have an event then, it works out quite well :)
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

stephen_usher
Posts: 2158
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
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Re: General Stuff(tm)

Post by stephen_usher » Thu Oct 14, 2021 6:12 pm

Well, it's not the ROMs. I wrote a couple of 27C512R with the Mac Plus rev.C images and nothing's changed.

So, the next test will be adding a 10K ohm resistor to see if that helps with the ringing. If it does then I'll add pull-ups on all address, data and control lines. The alternative is to add very small capacitors.
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.

stephen_usher
Posts: 2158
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: General Stuff(tm)

Post by stephen_usher » Sat Oct 16, 2021 7:39 pm

Today I received...

A heavily augmented BBC Micro. Heavily smoke tar covered and it came with a dual floppy drive and two large bags holding commercial floppy games and some tapes.

I've not changed the smoke generators in the power supply yet but I risked powering it up.

After reseating the Watford Electronics 12 ROM board in the ULA socket I got a Boo-Bip and it worked.

IMG_2440.jpg
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IMG_2441.jpg
IMG_2441.jpg (15.29 KiB) Viewed 138 times

The machine is HEAVILY smoke tar covered. Everything's orange, including the main PCB. It's going to need a lot of cleaning.

The H key needed a bit of persuasion to work so as to get the list of ROMs...

IMG_2442.jpg
IMG_2442.jpg (22.61 KiB) Viewed 138 times
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.

stephen_usher
Posts: 2158
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: General Stuff(tm)

Post by stephen_usher » Sat Oct 16, 2021 7:45 pm

Oh, and that round thing on the board is a battery. That needs removing NOW. At least it's not a VARTA
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.

stephen_usher
Posts: 2158
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: General Stuff(tm)

Post by stephen_usher » Sun Oct 17, 2021 6:22 pm

I didn't have time to look at the TT's cartridge port issue as I was working on the BBC Micro instead.

This morning I stripped it down, removed all the updates and prepared to change the X2 capacitors in the PSU, which seems to be a replacement as it has a date stamp of May '86 whereas the chips on the main board are from early 83. (Before I could tell this I had to clean off the tops of the chips as the smoke contamination was so bad that I couldn't read the markings!)

Having stripped everything out I put the two case halves into soak in the bath in warm soapy water.

The normal RIFA replacement was much as expected, other than getting sticky fingers from the tar. Fixed the broken VCC tab on the board and did a bit more cleaning. It's better than it was but still a bit mucky.

Then it was back to the bath and a lot of elbow grease. The soapy water helped a lot and I got the case halves as good as they can be. The water in the bath was orange by now, and this is after I cleaned off most of the stuff with soapy kitchen towel last night.

Anyway, after drying the case it was time to put things back together again... Then I remembered about the battery on the ROM board.

I thought it had not leaked but after removing it there were tell-tale signs. At least the juice hadn't gone far, just on the pad underneath and the leg of a nearby resistor. Cleaned that up and had "fun" reflowing the solder on the ground pad, removing the contamination in the process, which turned into a dark green goo when it reacted with the flux and molten solder. It doesn't look too bad now:

IMG_2452.jpg
IMG_2452.jpg (259.95 KiB) Viewed 101 times

Anyway, as the Haynes manual says, replacement is the opposite of removal...

Working machine! :-)

IMG_2450.jpg
IMG_2450.jpg (205.23 KiB) Viewed 101 times

I still have to pull all the key caps off and soak and scrub them, but the machine is operational and a lot cleaner.

Oh, and the previous owner had set the keyboard jumpers to boot into a different graphics mode from Mode 7, which confused me for a while.
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.

stephen_usher
Posts: 2158
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: General Stuff(tm)

Post by stephen_usher » Sun Oct 17, 2021 8:07 pm

Keyboard now clean. It's looking half decent now.
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.

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