1040 STF no floppy access and odd? change to board.

[tregare]

-sigh- am looking at a 1040 stf I picked up (as is) and there is no floppy happiness, get a little bee? icon on an attempted format, no floppy motor, no select light.

 

looking inside, someone has fiddled inside it, U43, the mostek 68901 has a solder splash on it, and someone has drilled a trace and put a 100 ohm resistor from c86 to one end of R41, and then unsoldered one end of C73 and soldered the end of that cap to where the 100 ohm resistor is soldered.

 

also someone has pulled and socketed U16, the yamaha TM2149F.

 

any suggestions on troubleshooting the floppy? I'm suspecting the sound chip or the floppy controller itself, with no motor on action IIRC it points to the sound chip as the 1772 FDC does not have it's own drive select lines and the sound chip handles the drive select (I think)

[OldAtarian]

Maybe someone tried to do a 1.44 meg floppy mod and screwed it up.

[Dal_1978]

-sigh- am looking at a 1040 stf I picked up (as is) and there is no floppy happiness, get a little bee? icon on an attempted format, no floppy motor, no select light.

 

looking inside, someone has fiddled inside it, U43, the mostek 68901 has a solder splash on it, and someone has drilled a trace and put a 100 ohm resistor from c86 to one end of R41, and then unsoldered one end of C73 and soldered the end of that cap to where the 100 ohm resistor is soldered.

 

also someone has pulled and socketed U16, the yamaha TM2149F.

 

any suggestions on troubleshooting the floppy? I'm suspecting the sound chip or the floppy controller itself, with no motor on action IIRC it points to the sound chip as the 1772 FDC does not have it's own drive select lines and the sound chip handles the drive select (I think)

 

Probably the best thing to do it remove the resistor, re-attached C73 to it's rightful place and repair the trace by scratching away either side of the drill hole and soldering a small wire (use part of the salvaged resistor's leg).

 

Then it would be wise to take some macro photos of the board and post them up here so we can confirm that there isn't any other 'mod' on the board that needs undoing.

 

I will try and grab a schematic and help you check it through. Once it is back to 'stock', then we can see if the problem was an unsuccessful mod, or whether the previous owner naffed the sound chip in the process!