Help needed fixing problem with a 520ST/FM

[Rybags]

Someone on another (not Atari-related) forum contacted me with a problem. He's got a 520ST/FM, and it's not working very well.

I suggested reseating chips, and the usual 4-inch drop, powering up without anything in the floppy drive, and trying it with the floppy drive disconnected.

I don't have access to the machine, but here's the problem description and what he's tried so far:

 

I've got this 520STfm in my hands now. Initially it gave nothing, but I popped it open and re-seated all the chips, and now I'm getting a white screen with 3 bombs. Any suggestions?

 

At the moment, when I hit power, I get a white screen. After about 10-15 seconds (the floppy LED lights twice), it quickly flashes up 3 bombs and restarts, rinse and repeat indefinitely.

 

If I disconnect the floppy drive from the little daughterboard thing, it sits at the white screen for about 10 seconds, then displays 2 bombs.

 

Nothing else I do has had any effect. I've reseated every IC that has a socket, blown dust out of everywhere, tried the 4 inch drop... all with zero benefit.

 

The floppy drive makes a horrible buzzing sound, but that is because the drive belt has disintegrated, so the spindle motor is spinning freely.

[+DarkLord]

Someone on another (not Atari-related) forum contacted me with a problem. He's got a 520ST/FM, and it's not working very well.

I suggested reseating chips, and the usual 4-inch drop, powering up without anything in the floppy drive, and trying it with the floppy drive disconnected.

I don't have access to the machine, but here's the problem description and what he's tried so far:

 

I've got this 520STfm in my hands now. Initially it gave nothing, but I popped it open and re-seated all the chips, and now I'm getting a white screen with 3 bombs. Any suggestions?

 

At the moment, when I hit power, I get a white screen. After about 10-15 seconds (the floppy LED lights twice), it quickly flashes up 3 bombs and restarts, rinse and repeat indefinitely.

 

If I disconnect the floppy drive from the little daughterboard thing, it sits at the white screen for about 10 seconds, then displays 2 bombs.

 

Nothing else I do has had any effect. I've reseated every IC that has a socket, blown dust out of everywhere, tried the 4 inch drop... all with zero benefit.

 

The floppy drive makes a horrible buzzing sound, but that is because the drive belt has disintegrated, so the spindle motor is spinning freely.

 

Sometimes, if you have a working, but very weak power supply, the ST will reboot when it gets to the

part in the boot process that involves floppy drive access. From my admittedly limited understanding,

this is because the floppy actually uses a lot of power.

 

Once you disconnect it though, it should go to a semi-blank desktop - unless the P/S is too weak even

for that. Any chance you can swap out a known "good" P/S and see?

 

HTHs.

[Rybags]

Unlikely. He's only just aquired this machine, and they're not real common around these parts anymore.

 

I suppose it might be possible though to just power the floppy off a PC PSU temporarily.

[AllanHiggins]

The fact that he's getting bombs at all is still a good sign, since the drawing of the bombs requires the CPU, ROM, and video to be working, at least working to some extent. If the machine got better, albeit marginally, after reseating the chips, then oxidation is at least one of the problems. Tell your friend to remove the chips again, but before plugging them back in wet the pins with WD40. Don't spray the WD40 directly on the pins, it's too messy and you don't want to create a short -- wet a cotton swab and brush the pins liberally. Don't leave any cotton fibers on the pins. The WD40 will aid conductivity.

 

Another thing you can tell your friend to do is leave the machine turned on for a while. 24 hours, perhaps. Just to get the blood flowing, so to speak. Circuitry wants to be used.

[Rybags]

He's tried powering the drive, and in fact the entire machine with a PC PSU but no joy.

 

Next up, he's tried a modified Sony disk drive:

I modified a Sony floppy drive to suit the system. When there is no disk in the system, it gives 3 bombs as usual. If I put a disk in. Any old disk. I get 11 bombs.

 

Line F error now.

[oky2000]

I'm sorry to say but this is going to be a motherboard fault or a non socketed IC on it's last legs, and unless he has a circuit tester and probes every cap on the board and other such tedious jobs it isn't going to work.

 

STFMs are peanuts in just about every country ebay exists...so unless he lives in Siberia the sensible thing is to salvage any useful parts and shelve those and go and spend $10 on a working machine!

 

If it was a rare edition or a Falcon then I can see the point in dicking around like this but seriously there is no need with the 520STFM clogging up any retro website with an Atari section.