Dead 1040 STf

Problems with your machine in general.
User avatar
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Dead 1040 STf

Post by sandord »

My 1040 STf suddenly died yesterday :shock:

Motherboard model: C070523-001 REV.D
There are no modifications applied to this ST, everything stock.

This is what happened:
  • ST didn't want to run colour monitor (SC1224, works great on my STfm) anymore (looks like 70 hz signal going out, screen running vertically, no distinguishable graphics)
  • Mono works fine still (SM124)
  • Started basic from the language disk
  • After a minute the ST froze, no mouse pointer visible but screen still visible
  • Power off, power on: nothing happens. Screen stays black (although a single frame can be seen with like 5% of non-blackness, looking distinctively like analogue distortion, nothing digital). The drive light doesn't light up. No digital activity of some sorts can be perceived.
What I've tried:
  • I always smell first (general life advice) but nothing out of the ordinary.
  • Disconnect the disk drive
  • Look for anything that could cause a short
  • Tried 3 different PSUs which all show decent Vpp readings on the scope when sitting in this ST
  • Pushed shifter firmly in its socket
  • Reseated glue/mmu chips after cleaning with cleaning alcohol
AND SUDDENLY IT WORKS!

The last steps were clearly the solution in my case, I already suspected the glue or mmu chips being the culprit here because apparently ram wasn't even accessed.

So while I fixed the problem while writing this post, I still wanted to share it because someone with the same symptoms might find it useful.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Dead 1040 STf

Post by exxos »

:bravo:

Glad we could help :lol:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Dead 1040 STf

Post by sandord »

:lol:
User avatar
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Dead 1040 STf

Post by sandord »

It's interesting though, how the ST would not switch to 50 Hz and keep sending 70 Hz to the colour monitor. That's probably the glue chip going out of its mind, right? I don't know too much about how everything works together but as far as I know the glue chip keeps the shifter constantly under control, including timings based on whether the ST runs in mono/colour. Right?
User avatar
DrF
Posts: 640
Joined: Thu Aug 17, 2017 1:18 pm

Re: Dead 1040 STf

Post by DrF »

Glad its working again and nothing serious :D

Is there some science behind chips coming loose suddenly almost 30 years later?
I've always wondered, there's no moving parts to wear out and its not like your waving the thing about all the time.

Thermal expansion/cycling??? tiny moves adding up over time to create a bad connection?
User avatar
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Dead 1040 STf

Post by sandord »

Yeah, I've heard this is design error on Atari's part. Thermal effects slowly causing the chip to creep out of its socket, regardless of the retainer bar.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: Dead 1040 STf

Post by rubber_jonnie »

It's weird, I have a test mainboard that I'm running a PAK accelerator in, but also had a memory upgrade that I had to remove, including removing the Shifter adapter, but I forgot to push the Shifter back into its socket, but it ran fine just sitting in the socket.
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
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Dead 1040 STf

Post by sandord »

rubber_jonnie wrote: Sun Aug 26, 2018 2:24 pm It's weird, I have a test mainboard that I'm running a PAK accelerator in, but also had a memory upgrade that I had to remove, including removing the Shifter adapter, but I forgot to push the Shifter back into its socket, but it ran fine just sitting in the socket.
I don't think pushing the shifter fixed my problem here, I'm pretty sure it was either the glue or the mmu. I did it just to be sure though.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: Dead 1040 STf

Post by rubber_jonnie »

I have run into issues with the PLCC socketed chips too, I think also one of the problems is that the contacts are not gold plated on either the chip or the socket, so there is a chance for both the chip pins and the socket pins to have oxidisation occur over a long period, which leads to poor connectivity, and that push can be enough to give the contacts a quick scrape and clean them sufficiently to restore contact.

I wouldn't rule out chip creep either 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...
User avatar
sandord
Posts: 673
Joined: Mon Aug 13, 2018 10:08 pm
Location: The Netherlands
Contact:

Re: Dead 1040 STf

Post by sandord »

Today the ST started acting up again. Somehow it seems to be stuck in 70 Hz for colour resolutions.

The screen flickers exactly like it does when holding the reset button. I can see the desktop and everything but the picture is running like crazy.

Sounds like a glue chip leg needs more cleaning...
Post Reply

Return to “HARDWARE ISSUES”