Picked up a 520STF, 1040STF & 1040STFM : Looking for repair resources.

[Gaetznes]

I'm a Atari ST / 68000 / 16 bit computer virgin. I have no experience with the 68000 based hardware beyond some minor arcade repair. Though, that was mainly eprom related.

 

So I picked up the three computers. Which i'm trying to identify going by the pcb. I've recaped and tested one of the psu's and have used this one to do all my testing. After checking voltage. I'm looking for advice, or at the least direction to sources to do my own research. Can't seem to google successfully "Troubleshooting" to the same success as say a Atari 8bit computer, Commodore 64 or Nintendo products.

 

Computers on hand

1. 520 STF / c070789-001 rev d

2. 1040 STF / C070523-001 rev d

3. 1040 ST / c103225 rev.1 or is this a 1040 STFM? I ask because that was the case it was in.

 

Status

All tested on the monochrome Hi Res Atari Monitor SM124 and Composite &/or RF on a Modern LCD. Green light in bottom left turns on for each of them. Each of them had psu and floppy drives inside. Pictures below.

 

1. 520 STF / c070789-001 rev d / Total black screen on Monochrome. No image on LCD. No audio when keys are pressed. 68000 cpu had significant corrosion, so I replaced it. No Change.

 

2. 1040 STF / C070523-001 rev d / Distorted image on Monochrome Monitor, nothing on LCD, Audible sound when key is pressed. Image changes slightly about a min after turning on the computer. Audible sound is no longer available when pressing key. Image reminds me of a RGB without sync.

 

3. 1040 STFM / c103225 rev.1 / Working, Tested on Hi Res Atari Monitor and Composite on a Modern LCD. Giving a extremely clear image. RF works on channel 2, but their is significant audio and visual static. I can't rf tune it in on this lcd. As recommendations have noted, that i've read.

 

 

 

Images

 

2. 1040 STF / C070523-001 rev d When first turned on. Sorta looks like the menu is skewed across the top.

2. 1040 STF / C070523-001 rev d, Min or so after turning on. Its as if it took that long for the cursor is now skewed or infinitly mirrored across the screen.

2. 1040 STF / C070523-001 rev d, PCB

 

1. 520 STF / c070789-001 rev d

 

3. 1040 ST / c103225 rev.1

3. 1040 ST / c103225 rev.1 Shown working

[tjlazer]

just as a note, you won't get composite out unless it has a RF modulator. Did you reseat all the socketted chips?

[spacecadet]

Yeah the "M" stands for "modulator". So it's not surprising that only the 1040STFM works via RF on the LCD. The others won't.

 

Kind of a dumb question but just to rule out the obvious, how are you actually connecting to both the SM124 and the LCD on the non-M computers? What port and what cable are you using?

[Gaetznes]

just as a note, you won't get composite out unless it has a RF modulator. Did you reseat all the socketted chips?

 

I have re-seated all the dip ic's, and none of the plcc's. I place to burn a new set of the rainbow tos eproms tomorrow. Also thanks for the composite / rf modulator info.

 

Since writing this earlier, I noticed on the 520 that a chip is piggy backing on another. You can see on the top left of the picture, of the mobo, U1 7405 ic. Ill remove that tomorrow.

[Gaetznes]

Yeah the "M" stands for "modulator". So it's not surprising that only the 1040STFM works via RF on the LCD. The others won't.

 

Kind of a dumb question but just to rule out the obvious, how are you actually connecting to both the SM124 and the LCD on the non-M computers? What port and what cable are you using?

 

To the SM124, im using the monitor connector. I wasn't originally aware of the no composite without a rf modulator. So i had actually made a test rig for a rca phono jack to the tv. using that 13 pinout online. so that explain that i guess.

[vattari]

There’s not much I can add other than once you connect a floppy drive to ST #4, you’ll get the floppy drive A: icon on the desktop

 

 

Sent from my iPad using Tapatalk

[Zogging Hell]

Few suggestions.. Are the ROMs in the 520 in the right order? They seem to have numbers labelled on them, has the original owner had them out and have they been put back incorrectly?

Also try swapping the shifter chip (if possible, is it soldered?) from the known good ST to the bad ones to see if that helps? (basically try swapping anything you can). This might help to pinpoint if one of them has had it. You could also try the MMU from the 1040 to the 520 to rule that out. There seems to be a modulator in the first 1040, or am I just seeing things? If it is and it really is a 1040 STF then it must be an after market (modulator) number, so it might be worth checking the connections (solder points) on that.

[Gaetznes]

 

Few suggestions.. Are the ROMs in the 520 in the right order? They seem to have numbers labelled on them, has the original owner had them out and have they been put back incorrectly?

Also try swapping the shifter chip (if possible, is it soldered?) from the known good ST to the bad ones to see if that helps? (basically try swapping anything you can). This might help to pinpoint if one of them has had it. You could also try the MMU from the 1040 to the 520 to rule that out. There seems to be a modulator in the first 1040, or am I just seeing things? If it is and it really is a 1040 STF then it must be an after market (modulator) number, so it might be worth checking the connections (solder points) on that.

 

 

After closure inspection, I determined that one of the previous owner had damaged several of the plcc ics. Also the 1040stf that has the modulator, was removed from the 520, as it was a FM. Swapping out the modulator between the two units didn't produce anything. But at this point I discovered the plcc issue. I decided to discontinue any additional work on the two defective units. Since then, I've dropped off the two non working units to a computer shop friend. That actually has a client with a non working 520STF on to do list. I'm hoping that something from those two can fix his. One less unit. Oh the roms (two prom set) were tested on the 1040STFM, they worked fine and were placed in the correct order.

 

On a sad note, I learned the hard way that the medium and low res games make me sick. I ended up vomiting after 45mins of game play. After a quick search on line, well after I could actualy get up and stare at a screen. Other gamers suffer from something called Simulator Sickness. Theory is basically vertigo. Though I figure its more to do with the refresh rate. As some of the games were simple like battleship. Either way, i'm disappointed as I was fine while testing it for several hours on several days and playing it in High res. The theory would explain why I can't play first or third person shooters. I've since found a friend to give it a nice home. Hes having a blast with it.

[Gaetznes]

There’s not much I can add other than once you connect a floppy drive to ST #4, you’ll get the floppy drive A: icon on the desktop

 

 

Sent from my iPad using Tapatalk

I eventually removed the Floppy Drive out of the external unit I had. It worked fine and did exactly as you said. Thanks