exxos's Atari, Amiga & retro forum

Hi Guys,

I'm working on one of my FMs and while I was checking it over last night I noticed that on the floppy header I added a few years back, there is a loose pin. it has been pushed through the board a little and on closer investigation, I can push and pull it through the board with tweezers.

It -appears- to be pin 16 'motor b enable'

is this a pin thats actually used on the ST ? there doesn't seem to be a solder pad or trace running to on the bottom of the board, but I'd like to know if it's going to stop the drive a working before I start cutting chips off :)

will grab some pics this evening.

cheers :)

spiny wrote: 23 Aug 2017 08:35
is this a pin thats actually used on the ST ? there doesn't seem to be a solder pad or trace running to on the bottom of the board, but I'd like to know if it's going to stop the drive a working before I start cutting chips off :)

"Motor On" is exactly that. It turns the floppy drive motor on (makes the floppy spin).

I actually use that signal on my V6 floppy kit as some AND type logic to enable 16mhz mode.

The copper track may well be on the top of the board. Resoldering likely going to be a issue if it is under plastic. Assuming the via is not damaged, you could try placing some flux on the pin and trying to resolder it, see if the solder will "suck" back into the hole and solder the pin back.

Either that , or see if you can remove the plastic and resolder from the top. If the track is damaged, then you will have to solder a wire to the pin to reconnect the motor on signal.

bums.

I'll try a careful re-flow from underneath first.

still, the more I solder, hopefully the better I will get :)

spiny wrote: 23 Aug 2017 10:13 bums.

I'll try a careful re-flow from underneath first.

still, the more I solder, hopefully the better I will get :)

At least you are trying, which is more than can be said for a lot of people :)

Let us know how you get on :)

but just to confirm, pin 16 is motor B enable, not motor A (pin 10 seems to be motor A) , so will having it N/C just mean that if I connect a Dribe B, it won't spin up ? if thats the case, i'll leave it as it is, rather than potentially screw it all up even more.

spiny wrote: 23 Aug 2017 11:36 but just to confirm, pin 16 is motor B enable, not motor A (pin 10 seems to be motor A) , so will having it N/C just mean that if I connect a Dribe B, it won't spin up ? if thats the case, i'll leave it as it is, rather than potentially screw it all up even more.

I'm not at home right now to check' but IIRC motor A&B are the same signal.

I took a quick look at the schematics and pin 16 is Motor On. Both the internal connector and the external floppy plug are connected to that pin on the mother board (going through a 74LS06 gate) from the FDC pin 20. So they are the same signal.
If the track is broken you might be able to run a small wire from the ferrite beads that is between the connector and the 74LS06 (U14 on the 1040 STFM schematics) pin 8. The schematics is hard to read but it looks like its the filter bead 224.
Rodolphe

pics, as promised:
the pin i'm pointing a scalpel at is the loose one in the top view, hopefully it's more obvious which pin it is on the bottom view :)

note: the extra wire on the WD is where i've removed an old HD/DD switcher board.

Likely is PCB track running on the top. Try to resolder as I suggested, Check with a meter the connection as Rodolphe suggested. If track is broken, then you will have to wire link it back up.