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Offline ognixTopic starter

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Erroneous floppy-in-drive problem
« on: October 26, 2010, 10:30:37 PM »
ERRONEOUS FLOPPY-IN-DRIVE PROBLEM

Hello everybody!
Here I just want to explain how to solve a problem I encountered in my A600HD (recently acquired through a friend of mine): it came in very good cosmetic conditions, but it had a problem with its floppy drive, and a "loosy" Kickstart socket (which I still have to change with a high quality and low profile one).
The solution applies also to all other Amigas and different floppy drive models: you just need to change few details.
In this little tutorial I assume you can easily disassemble your Amiga and drive, and that you have basic skills of electronics.
The entire operation will take you around 2 hours (maybe less), for doing a calm and good job.
In any case I won't take any responsability for any damage done.

What happens...
When the Amiga starts up, it seeks for a floppy disk for a while, and then goes back to the startup screen (the hand or the violet screen, depending on your KS), if you have no hard disk installed.
Once you insert a floppy disk, nothing happens.
The only way to load disk is to reset the machine.
Of course even after boot up, disk change is not recongnized (sometimes happens, but this is due to the nature of the fault - read later).

Where's the problem?
The floppy drive model I got on my A600HD is the Teac FD-235F, a double density model, of course.
Pictures here are related to this model, but a similar approach can be applied to any floppy drive with this symptoms.
As you may guess the problem is located into the switch that checks for the presence of a floppy disk (as well as for write enable signal).
Check out the first picture to locate it: it may differ a bit if you have another floppy drive model (there's plenty of).

How it works
To let the Amiga know there's a floppy inside the drive, the NC (normally closed) switch become open as soon as the disk is inserted completely (same applies for the write enable switch).

What's the problem...
Over time contacts inside the switch (but also in the outside) become oxidated: they get really black (at least in my case), not even opaque grey.
Due to this reason the NC switch becomes NO (normally open) permanently, indicating a floppy disk inside even if it's not.
Sometimes moving the disk body, stressing the switch a bit, makes it work again for a while, but not that long.

How to solve the problem
Firstly do not use WD-40 or similar stuff for "mechanical" environments: it won't work also because it difficult to get the liquid inside the switch.
To do a good job you have to remove the double switch from the drive and open it!
Once you removed the drive from your Amiga, open the bottom lid, to access to the lower PCB where the switch is soldered (Picture 3 and 6).
Place some new tin on solderings and remove it completely from the board.
Rise up the 3 pins with a small screwdriver from the PCB, while heating a bit with your soldering iron.
After this, remove the 4 screws that fix the PCB in place (Picture 6).
By doing this you can now "slide away" the switch from the front by rising up a bit the PCB.
Now you have the switch in your hands!  :)
Now you are in the most "risky" part of the job: you have to open the switch itself!
It's quite small, and it's made of two parts: you have to take away the transparent part on the bottom to access the inner contacts.
For doing this you have to force with a very little screwdriver around the edges: you'll notice there are some clips; much probably you'll brake those clips, but it's inevitable (you may try to warm the plastic a bit to make it softer).
At this point take MUCH CARE because inside you have 2 little springs and 2 little contacts: open the bottom part carefully, trying to avoid the springs to jump outside! (otherwise it will be a "seeking for a spring on the floor" times)
Check picture 4 for a clue.
Once you have the 2 springs apart, remove the little contacts and the "stick buttons" as well.
Look inside the switch (with a lamp) and you'll probably see just black stuff: check out picture 5 and use the same little screwdriver for scratching oxidation away from them; you have to be very patient.
Do the same with the little contacts gently, paying attention not to brake them nor to bend them that much (they are bent for a reason).
After doing this:
- place the "button sticks" back inside again (paying attention to the "notch");
- use some contacts cleaner if you want (just a bit - use something for electronics);
- place the 2 little contacts back, with their central part up to you, so they make contact on the bottom;
- CAREFULLY, with little pliers, place the springs back in place, with their larger part towards you;
- don't breath :) and with MUCH CARE place back the bottom part of the switch, taking care of the springs (to locate them at the right place, and not let jump away);
- after this you're almost done: use some glue to fix the bottom part of the switch (or some adhesive tape, it's up to you).
Just to be sure check the contacts with a multimeter: if I remember well, the first one on top (Picture 5) is the common central one, the second one is the rightmost contact, while the third on the bottom is the leftmost contact.
Without pressing buttons the are all short circuited; by pressing either one or other button you'll lose contact between the common and the related pin.
Once you've done this, place the switch back to drive PCB by sliding it in; place back the 4 screws on PCB and solder the 3 pins on it.
You are done!
Before closing the drive I suggest you to open also the upper lid, and take some time to clean drive heads (with MUCH CARE) with isopropylic alchool and lubricate moving mechanical parts.
Place back your drive into your Amiga and enjoy your time!  :D
 

Offline Franko

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Re: Erroneous floppy-in-drive problem
« Reply #1 on: October 27, 2010, 12:26:18 AM »
I've came across that problem many times before in the past, I've found just a little squirt of contact cleaner or WD40 on the switch and a few rapid presses of it soon solves the problem... ;)
 

Offline ognixTopic starter

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Re: Erroneous floppy-in-drive problem
« Reply #2 on: October 27, 2010, 12:28:30 PM »
Hi Franko!  :)
Yes, it may work most of time, but I think it won't last for years as a complete removing of oxidation.
In my case contacts were REALLY black!

Of course it's a matter of few minutes of work against almost two hours!
...and a couple of years against maybe 12/15 years of correct drive behaviour.

It depends on you! :)
By!