Atari 520 STE - Joystick port failure

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Dlfrsilver
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Atari 520 STE - Joystick port failure

Post by Dlfrsilver »

Hello, i'm writing here because one of my friends (a musician) bought for cheap a 520 STE, and it appears that the joystick port UP position is stuck to "high". When he use a game, the sprite is permanently jumping up without stopping.

He has already reflowed the solders (they were broken, like most of the time). But this has not changed a thing.

What would you advise Exxos ? Could it be the beyboard buffer (74LS244) ?

Thank you for reading me :)
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rubber_jonnie
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Re: Atari 520 STE - Joystick port failure

Post by rubber_jonnie »

Has the keyboard been tested otherwise and found to be working? Does the mouse port function as expected? Also, does the problem occur with the joystick removed?

I'd suggest that if the KBD processor is socketed, you remove and re-seat it, cleaning the pins on the chip and using Deoxit or Electrolube on the socket.

I'd also suggest a close up examination of the PCB for cracks and/or shorts using a magnifying glass, microscope or possibly use a multimeter in continuity mode.
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...
Dlfrsilver
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Re: Atari 520 STE - Joystick port failure

Post by Dlfrsilver »

rubber_jonnie wrote: Tue Aug 25, 2020 9:39 am Has the keyboard been tested otherwise and found to be working? Does the mouse port function as expected? Also, does the problem occur with the joystick removed?

I'd suggest that if the KBD processor is socketed, you remove and re-seat it, cleaning the pins on the chip and using Deoxit or Electrolube on the socket.

I'd also suggest a close up examination of the PCB for cracks and/or shorts using a magnifying glass, microscope or possibly use a multimeter in continuity mode.
Ok :

- The keyboard is working from what said my pal, and also the mouse. The solders have been redone on both mouse and joystick ports.
- The problem occurs with the joystick removed.
- the IKBD MCU has been removed and replugged in its socket.

EDIT : with the keyboard PCB unplugged from the motherboard, the sprite is still jumping permanently ! so the problem is on the motherboard :(
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stephen_usher
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Re: Atari 520 STE - Joystick port failure

Post by stephen_usher »

Does it happen with the mouse disconnected? Joystick fire is the same as mouse button 2.

Check for solder bridges on the mouse port in case mouse button 2 line is bridged.

I had something similar when using a "Tom" USB mouse to ST adapter. There was no diode on the button 2 line so it was compensating for the joystick button switch in the circuit, meaning that the joystick fire button didn't work.
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: Atari 520 STE - Joystick port failure

Post by rubber_jonnie »

Dlfrsilver wrote: Tue Aug 25, 2020 10:21 am
rubber_jonnie wrote: Tue Aug 25, 2020 9:39 am Has the keyboard been tested otherwise and found to be working? Does the mouse port function as expected? Also, does the problem occur with the joystick removed?

I'd suggest that if the KBD processor is socketed, you remove and re-seat it, cleaning the pins on the chip and using Deoxit or Electrolube on the socket.

I'd also suggest a close up examination of the PCB for cracks and/or shorts using a magnifying glass, microscope or possibly use a multimeter in continuity mode.
Ok :

- The keyboard is working from what said my pal, and also the mouse. The solders have been redone on both mouse and joystick ports.
- The problem occurs with the joystick removed.
- the IKBD MCU has been removed and replugged in its socket.

EDIT : with the keyboard PCB unplugged from the motherboard, the sprite is still jumping permanently ! so the problem is on the motherboard :(
It could be that there is a problem with the 74LS244, and it is cheap and relatively easy to replace, but it sounds a bit unlikely. I'd be looking for shorts, solder bridges or other damage.
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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PaulJ
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Re: Atari 520 STE - Joystick port failure

Post by PaulJ »

You should take a look at the connectors where they are soldered onto the keyboard. They tend to have solder broken from the tension put on the them plugging and unplugging. Much more like likely than a defective chip.
Dlfrsilver
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Re: Atari 520 STE - Joystick port failure

Post by Dlfrsilver »

PaulJ wrote: Tue Aug 25, 2020 2:48 pm You should take a look at the connectors where they are soldered onto the keyboard. They tend to have solder broken from the tension put on the them plugging and unplugging. Much more like likely than a defective chip.
Sorry, my pal already redone the soldering of the connectors. And it appears that the problem appears even when the keyboard PCB is unplugged from the motherboard.

Possibly the ACIA 6850 ?
tzok
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Re: Atari 520 STE - Joystick port failure

Post by tzok »

Keyboard IKBD is connected over serial line to the second (U201) ACIA. If joystick is permanently read up, then there is no other explanation than bad ACIA.
Dlfrsilver
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Re: Atari 520 STE - Joystick port failure

Post by Dlfrsilver »

Problem found and solved : it was the 74LS247 under the keyboard ! This shit was broken and not working. I advised my friend to replace it, he did it, and tada ! his STE is working again, both mouse and joystick !
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