A500 floppy drive LED problem

[Bastich]

Hi all

I have recently been attempting to repair a dead A500+. As expected the battery had made a good mess of the board and killed Gary and the socket. Since the initial clean up I have removed the damaged socket, nearby resisters and stripped the motherboard lacquer around the effected area. Once this was done I managed to find one broken track which I have repaired and then applied new lacquer. After certifying the tracks around the battery etc I have fitted a salvaged socket and Gary to the board. I was very happy last night as after all my hard work the system works almost perfectly. The main problem remaining is that the floppy drive LED does not come on when in use. The drive itself works fine including its own onboard LED. I have tried 3 different keyboard controllers and all do the same (I prefer the red power /caps LED). Does anyone have any ideas why the floppy LED dies not light? The system loads disks plays sound everything other than the floppy LED. I will update this thread with some pictures later tonight.

 

[ptp170]

I think the Amiga feeds the signal from the Motor on the floppy drive to the keyboard so you may have a break somewhere...

---------- Post added at 17:52 ---------- Previous post was at 17:49 ----------

Look at the top right of Page 7 on the schematics for the _MTR0 label

http://www.amigawiki.org/dnl/schematics/A500_R6.pdf

and now look at the internal floppy header on Page 8 pin16



Test for continuity between Pin16 and R504/R506. If it's ok then Q503(2N3906) may be toast but that should be easy to check with the diode checking function on your multimeter...

 

[Bastich]

Awesome
I will check for that as soon as I get in later.

 

[Bastich]

Just replaced Q503 after confirming it was dead
I took the replacement part from my spares board (Very very dead A500+).
This part passed the multi meter test thou with consistent values.

Thanks for the advice you were spot on

The only issue (which I only just spotted icard) is with the floppy drive itself.
If a disk is in to start with all is good
However as soon as you take a disk out or boot without one in the drive starts up and then does not accept any other disks.

If I unplug the power to the drive, put a disk in and then re plug it it works fine.
It seems as thou it thinks there is a disk in when there isn't???
I am assuming this is just the drive and will try and confirm it once I have dug out a known working unit.

Also the screen dims very slightly when the drive moves the head.
Could this be a capacitor issue???
None of them are bulging or anything and the PSU works perfectly on my other A500s and A600s.

 

[ptp170]

The disk change signal probably isn't being triggered.... See this video...

http://youtu.be/u2Ys0ucwNEQ

Have you tried measuring the 5v at various points on the motherboard when it is running?

 

[Bastich]

That video and the fault it shows matches what I am seeing
After a bit of poking it has started working so definitely just a sticky switch
Thanks for all your help and suggestions
Only other utility I could do with would be a memory tester.
Any recommendations?

 

[roy_bates]

i was going to say spray a little switch cleaner in the front of the little switches in the front of the drive.

if you have a couple of expansion cards for the 500 that has sockets you could use those as a memory tester.
you could even track faulty ones down individually that way.

if you mean software,there is plenty on aminet.