It's 600XL time!

Blogs & guides and tales of woo by forum members.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

So, a very quick bit of lunchtime diagnosis on the 600XL and I have found that there is no address line activity at all on the RAM chips at all. No RAS or CAS activity either.

I see some on the ROMs and Sally, and though I do need to check the rest of the ICs, I need to take a closer look at the logic sitting in front of the RAM.

So that's a bunch of LS logic chips, and those I can test with my TLS866 :)
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: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

And one is dead according to the TLS866, a 74LS51, quite a key component, and the one of the few 74LS logic chips I don't actually have to hand!!

Hopefully they will arrive soon!
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: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

rubber_jonnie wrote: Fri Jan 14, 2022 2:03 pm And one is dead according to the TLS866, a 74LS51, quite a key component, and the one of the few 74LS logic chips I don't actually have to hand!!

Hopefully they will arrive soon!
EDIT - The remaining 74LS logic chips all test good, and given that the failed 74LS51, U16, is slap bang in the middle of the CAS/RAS circuit:

Screenshot 2022-01-14 at 14.35.23.png
Screenshot 2022-01-14 at 14.35.23.png (1.82 MiB) Viewed 2364 times

Then I think I definitely need to change it.
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...
tzok
Posts: 337
Joined: Sat Dec 30, 2017 2:27 pm

Re: It's 600XL time!

Post by tzok »

Don't fully trust TL866 in terms of TTL testing, especially those less common. There are mistakes in the test vectors, verify them first.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

tzok wrote: Fri Jan 14, 2022 4:29 pm Don't fully trust TL866 in terms of TTL testing, especially those less common. There are mistakes in the test vectors, verify them first.
Fair comment, I will have a look.
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: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

Well the replacement 74LS51 arrived but made no difference.

Better do some proper diagnosis then :lol:
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: 5580
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: It's 600XL time!

Post by stephen_usher »

More oscilloscope fun! :-)
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: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

stephen_usher wrote: Sat Jan 22, 2022 4:50 pm More oscilloscope fun! :-)
Indeed!! My scope has never seen so much action!

I'll also use my TL866 Pro to check the new ICs, but it might be the case that @tzok is correct and the 74LS51 has a bad logic table in the software, so doesn't test right, and I haven't got round to checking the vectors yet.
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: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: It's 600XL time!

Post by rubber_jonnie »

Ok, so checking the new 74LS51s reveals that it looks like the TL866 test vectors are bad, but I have dropped a new IC in anyway.

I'm seeing activity on the address lines, but some just don't look right, and I do see CAS/RAS activity on the RAM during power up, so that's something.

I am concerned that Sally may have expired as she is extremely hot quite soon after power up, and what with the weird address line activity too, it's definitely a concern.

Clocks are all good at Sally too and elsewhere on the board.

I suspect that the GTIA and ANTIC are probably ok as I do get a picture, albeit a wrong one. More digging needed and the 800XL is going to have to be opened up, see if I can borrow any socketed parts for testing, though I have a horrible feeling Sally is socketed in the 800XL. We'll see.
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: 5580
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: It's 600XL time!

Post by stephen_usher »

Poor Sally.
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.
Post Reply

Return to “MEMBER BLOGS”