Atari STe 1040 - Joystick fault

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fattonytm
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Atari STe 1040 - Joystick fault

Postby fattonytm » Wed Nov 07, 2018 10:00 pm

Well I have a joystick fault on my Atari STe 1040! I have a Cheetah 125+ which initially seemed to work but after 5 minutes of playing the fire buttons stop working. Checked all the contacts in the joystick, cleaned the contacts but still the same issue, 5 minutes of full function then the fire buttons stop working.

I know dry solder joints are an issue but this doesn't seem to replicate dry solder joints, but does seem to identify a capacitor or logic ontroller fault. Anyone experienced the same problem and know what component(s) to replace? I'd assume it would be the logic controller/capcitors located under the keyboard PCB?

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Re: Atari STe 1040 - Joystick fault

Postby Greenious » Thu Nov 08, 2018 8:52 am

The keyword here is "5 minutes", is it really like exactly 5 mins or is it random?

You always resolder the mouse/joystick ports whenever you open up the keyboard because of the wear and tear these ports are subjected to, not so much that they were badly soldered from the beginning... after some use, a loose contact is more or less guaranteed.

Other than the mouse/joystick port needing resoldering the keyboard is in my experience very resilient.

https://www.dev-docs.org/docs/ got a Mega ST schematic "Atari Mega ST2/ST4 Schematic (Rev 9, C100166)", page 8 & 9 contain a schematic of the keyboard (the same is used on all st/ste/tt/f030).

as you can see, the signals from the joystick port pass through a line filter, then have a 10k Ohm pull-up resistor, and after that the mouse/firebuttons are connected straight to the IKBD. Obviously reseating socketed chips never hurts.
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fattonytm
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Re: Atari STe 1040 - Joystick fault

Postby fattonytm » Fri Nov 09, 2018 12:36 pm

I will reflow the solder once I have it all apart as you just mentioned, it doesn't hurt to do this.

Regarding the time it takes for the fire button to stop working is probably around 5 minutes, its not that random as its happened everytime, to a point where I can predict when its about to conk out. The fire buttons will intermittently operate but requires 10-20 clicks before I get a trigger. Once I power down and re-initiate the STe, it seems to work again for another 5 minutes, 2 games were tested. The cable plugging into the Atari is fixed using blu-tak (stops movement of the 9-pin connector which caused issues with my mouse originally but this is probably the cable).

It feels like a logic controller fault just because of the way it acts, similar to a floating gate, but the link you've provided will help me perform a proper diagnostic on this. It does seem like an unusual problem!

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Re: Atari STe 1040 - Joystick fault

Postby mpattonm » Fri Nov 09, 2018 3:51 pm

I would check the voltage levels on ACIA chip with oscilloscope. It may be the power supply is failing to cover increased consumption of system under load, causing voltage drop below operational levels. This scenario is yet more probable, if the PSU and mainboard have not been recapped yet.

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Re: Atari STe 1040 - Joystick fault

Postby fattonytm » Tue Nov 13, 2018 10:40 am

Excellent suggestions guys, thank you! Regarding voltage levels...I think there's something iffy going on when the STe will stop loading games and black screen now and again, I just took it as bad floppy disks or a dirty floppy drive head (how much innuendo can you make from that!) I will look into these as soon as I take the STe apart, now its getting the time to do it!

Just out of interest, any idea on the number of caps which would be replaced within the PSU? or is it wise to do the motherboard as well? I've performed a re-cap on Spectrums so its no big deal :coffe:

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Re: Atari STe 1040 - Joystick fault

Postby mpattonm » Tue Nov 13, 2018 8:40 pm

Look here for the motherboard part: https://centuriontech.eu/product/1040ste-recap-set/
As regards to PSU, it depends on what model you have in.

PS: The recap might not go as easy as on Speccy.


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