Atari STF Modulator

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TeX38
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Atari STF Modulator

Postby TeX38 » Sat Apr 29, 2017 8:49 am

Hi everyone,

I have an Atari 512 STF, and have purchased a modulator for it.

Sadly this fails to work.

to fit the modulator, I had to remove a few components from the modulator area of the motherboard, ie. some diodes, resistors and a transistor.

Do I have to solder any jumpers in that area or other areas for the modulator to work?

The motherboard version is C070523-001 Rev D.

Also, I would like to upgrade the ram, there are empty pads ready to take the new chips, but do I have to set any jumpers for this to work?

I also have a non working 1040STFM version C103414-001 Rev 1.1. motherboard.
I have found all the clock freqs to be correct but there is absolutely no data bus or address bus activity.
Any ideas?

Thanks.

Terry.

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Arne
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Re: Atari STF Modulator

Postby Arne » Sat Apr 29, 2017 10:57 am

Grab the Service Manual, read the chapter "Troubleshooting a dead unit" and then check /HALT, /RESET and /BERR.
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TeX38
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Re: Atari STF Modulator

Postby TeX38 » Sun Apr 30, 2017 12:53 am

Thanks Arne,
I got the manual, and HALT is being held LOW, there may be a fault with the 556, and/or the ls05, I removed the 74LS05 and HALT is still being held LOW.
Faulty CPU maybe?

RESET and BERR are both high.

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Arne
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Re: Atari STF Modulator

Postby Arne » Sun Apr 30, 2017 4:33 am

/HALT is bidirectional.
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TeX38
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Re: Atari STF Modulator

Postby TeX38 » Sun Apr 30, 2017 9:59 am

Yer, makes it more difficult to trouble shoot.Wish I had a diagnostic cartridge. be very handy.


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