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Mostly-functional 520STf


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Hi there, I somehow purchased what seems to be a non-functional 520STf from eBay a couple months ago. The system powers up, but there's no disk access (apparently someone tried to put a PC floppy in the machine?), and there's this horridly high-pitched squeal from the computer overall. Opening the case reveals no RF shielding whatsoever (as it doesn't have the TV modulator or the holes cut out for it, apparently). Is there any way in which I can bring the computer back to functional status once the RGB cable for my 1084S-D that I ordered for the Atari computer arrives?

Edited by NightSprinter
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  • 4 weeks later...

You mean you power it up and you get a green screen with no icons? Or white screen? If black screen, computer is DEAD, white means semi functional (try 4" universal drop) and green with no icons means dead or no drive connected.

Edited by tjlazer
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Here's the clincher. I just got my monitor cable for my 1084S-D2 monitor, and when I powered the system on (yes, switched the RGB system to Digital) there was no GEM desktop. Did something happen that I wasn't aware of?

The ST does not use digital RGB, it's analog. Digital RGB is for the C128.

 

As far as the squeal (if it is coming from the computer), unplug the power from the floppy drive and try. If its still squealing then I'd say its your power supply making that noise.

 

Make sure that noise isn't coming from your monitor being driven incorrectly!

Edited by remowilliams
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Ok, when I set it up to analog RGB I just saw nothing but green and purple bars scrolling. Are you sure it's analog RGB for the ST and up?

Positive. The ST/Amigas are analog RGB. TTL (digital) RGB is used by the C128 and EGA type PC monitors.

 

I have several STs and several 1084 monitors - one is a 1084S-D1 I believe analog is the button pushed in, and TTL is out.

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Just did so, still the rolling green and purple bars. I did find out the power supply seems to be bad, so I'll have to order a new one from Best Electronics next paycheck. That, plus I need to get some screws to keep the top half of the case still, despite I don't have the top half of my computer's RF shield.

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  • 3 months later...

Just did so, still the rolling green and purple bars. I did find out the power supply seems to be bad, so I'll have to order a new one from Best Electronics next paycheck. That, plus I need to get some screws to keep the top half of the case still, despite I don't have the top half of my computer's RF shield.

 

Very likely your ST has some more serious failure(s). With approach like this you will spend lot of money to fix it.

Ordering power supply, cable, floppy for it will cost more than buying functional machine.

There is even possibility that machine is in very bad condition, with lot of bad chips - if someone opened it he could replace good chips with bad ones, and selling so...

Not to mention that bad power supply can kill many chips in moment.

 

Littlest problem is PC floppy drive in - it works with ST, and only problem may be bad floppy change detection, but it is solveable: http://www.ppest.org/atari/flomodam.html

 

If you are lucky, there is possibility that there is just no sync. Maybe fixing cable will solve it....

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No, there's no RF Modulator in the 520. I've checked many times. Plus on the screen problem, I'm quite certain now that it's a problem with the sync lines for the monitor cable. The picture was a little more viewable if only plugged in partially (albeit a lot of buzzing from the speakers on my 1084S and the colors aren't exact).

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Well I'll be damned. The top of the case itself says 520STfm, but the board (and also the bottom half of the case) lacks anything for the RF modulator.

 

Would it not be cheaper to get another STFM? Ive had to do a few parts swaps to revive some machines at the expense of others.

 

JW

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Does the MB have 1MB RAM on it? maybe it is a 1040ST MB. I have a 520STfm with 1MB here, but has a 360k drive in it! Doh!

 

Well well.. it is INDEED a 1040STf board. I just did a Google search for the part number: C070523-001 REV. A, what few results that returned all point to it being the board to the 1040STf. Must have been upgraded or replaced at one point? Because I can see the cutouts in the plate shielding for the RF MOdulator, but no cutouts on the plastic itself.

 

Also forgot to mention, only the top half of the case is from a 520STfm, the bottom half says "1040STFM".

Edited by NightSprinter
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