I've been Coleco'd

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rubber_jonnie
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Re: I've been Coleco'd

Post by rubber_jonnie »

stephen_usher wrote: Mon Oct 07, 2024 12:03 pm Looks like an address line issue. Check for shorts. Probably one of the higher address lines.

What you get on the screen very much depends upon the mode the VDP is in and what graphics planes are being used as to what memory it will use.

The PAL version of the TI99/4A does use the same chip, as does the Memotech MTX, MSX-1, Spectravideo etc.

I should have one in stock if necessary.
Yes, that's my understanding too, and I appreciate the offer of one, thanks.

Funnily enough the address lines were next on my list of checks based on this from the service manual:

Screenshot 2024-10-07 at 12.45.09.png
Screenshot 2024-10-07 at 12.45.09.png (182.79 KiB) Viewed 94 times

Basically if the VDP is good it's one or more of the RAM chips, if not then the VDP is bad...

It does then go on to say check the CPU and system ROM (U1 and U2) but since the games are running, I think that they are fine.

However I did just do a continuity test on the address line of the RAM and found pins 6 &10 in the sockets are not connected to each other, however if I flip the board and run the same test, they are. I need to go away and verify that as it seems a bit weird to me and I need to check my work.
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...
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rubber_jonnie
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Re: I've been Coleco'd

Post by rubber_jonnie »

OK, so actually the pin 6 &10 thing was just me being an eejit, please ignore, the address bus from the VDP to the RAM and sockets seems to be fine.
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...
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stephen_usher
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Re: I've been Coleco'd

Post by stephen_usher »

No shorts between address lines then.
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: I've been Coleco'd

Post by rubber_jonnie »

OK, so the address lines all correctly buzz out to the VDP, all the RAM I'm using tests fine, so I think it can only be the VDP now, nothing else makes sense.

@stephen_usher you mentioned you might have a spare TMS9929A, if so can you let me know how much you'd want for it please?
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...
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rubber_jonnie
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Re: I've been Coleco'd

Post by rubber_jonnie »

stephen_usher wrote: Mon Oct 07, 2024 2:38 pm No shorts between address lines then.
Nope, all clear. I also checked at the VDP as well, no address line shorts there either.
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...
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rubber_jonnie
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Re: I've been Coleco'd

Post by rubber_jonnie »

Woo hoo!!!

ColUSB will be here tomorrow :)
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...
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rubber_jonnie
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Re: I've been Coleco'd

Post by rubber_jonnie »

Well, it seems I've been well and truly Coleco'd...

The ColUSB power supply arrived and on testing it I get this:

IMG20241008133348.jpg
IMG20241008133348.jpg (267.72 KiB) Viewed 54 times
IMG20241008133314.jpg
IMG20241008133314.jpg (239.22 KiB) Viewed 54 times

I'm letting it burn in for a bit to see what's what, but looks like maybe I've been fighting a power issue with my PSU lash up :dizzy:

I'm guessing that the Electron PSU was not up to snuff in the 5v or -5V department. Arrrrggghhhh

Well, lets see how the burn in goes...

:crossed2:
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...
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stephen_usher
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Re: I've been Coleco'd

Post by stephen_usher »

:dualthumbup: :yay2: :cheer:
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
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Re: I've been Coleco'd

Post by rubber_jonnie »

Well, about an hour in and it's still running just fine :)

Given that the VDP only requires 5v I'm assuming that the Electron PSU did not have enough power on the 5v line.
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...
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stephen_usher
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Re: I've been Coleco'd

Post by stephen_usher »

Or the -5V and 12V wasn't enough for the 4116 chips.
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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