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SomeGuy
July 19th, 2014, 12:26 PM
I know it is a bit of a long shot, but does anyone happen to know if there is a suitable replacement part for the photo-transistor index sensor available? There is no part number on it.

It is shorted on one side, and testing with one borrowed from an identical drive let the drive work properly.

This is on a Fujitsu/Copal m2551a 360k half height floppy drive.

I tried looking on Mouser, and found this: http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/QSE114/?qs=PzUwjIhihRvgEDEZWsCbOA==
But they have several versions that differ only in the described "mA" rating, and I'm not even sure if I am on the right planet anyway.

19535

I have a number of these Fujitsu 360k drives, and they have always been very reliable. This one has been in my parts box forever and the damage was probably something I did to it ages ago.

Chuck(G)
July 19th, 2014, 01:10 PM
The current rating shouldn't matter in this appliction, as I'm pretty sure that the output is simply used to drive a gate, so we're probably talking about 10 ma tops. More important would be the spectral sensitivity, although the Fairchild unit you pointed to should work.

Beware, however, not all things that look like phototransistors are. In particular, 3-terminal IR receivers used for remote controls are quite complex ICs that are sensitive to modulated (usually about 30KHz) light and blind to everything else.

3pcedev
July 19th, 2014, 04:24 PM
I think this one might be more suitable for your application:

http://au.rs-online.com/web/p/phototransistors/4557954/

The one you posted from Mouser doesn't have an internal transistor amplifier (hence it's only a 2-pin device; which is shown in the datasheet). Its annoying that Mouser show the representative image as having 3 pins.

Looking at the Datasheet the RS part will work well; its designed for a TTL interface plus it's matched to IR. As Chuck said though there is no guarantee that the IR wavelength will be the same; but I would say it's likely that this will do the trick.

SomeGuy
July 20th, 2014, 12:39 PM
Hmm, mouser has that OLP550 part listed under "Photo IC Sensors" http://www.mouser.com/ProductDetail/Optek-TT-electronics/OPL550/?qs=NVJATC80C4/p3S1CoM6V8g==

Chuck(G)
July 20th, 2014, 02:12 PM
I'd buzz out the three leads to find out which you need (simple phototransistor or phototransistor + amplifier). One pin is sure to be ground, but take a look at the other two. If you're unsure, I've got a couple of those 2551 drives here, somewhere and can check for you.

SomeGuy
July 20th, 2014, 05:09 PM
Ok on a working drive, pin 1 (from left to right on the photo) is ground, pin 2 is 0v when the light source is blocked or 5v when it is not, pin 3 is +5v.

That much matches the OLP550.

So this isn't just a plain phototransistor. I guess part of my confusion was that many other drives do just use a plain phototransistor, so teh googles wouldn't tell me the right term for it.

SomeGuy
July 31st, 2014, 07:53 AM
Yay! It's working!

I did run in to one problem, however. The black plastic housing that the index sensor board attaches to is exactly fitted to the size of the photo IC sensor. And the OLP550 is just a hair larger (or perhaps I didn't get the pins angled in just the right place, hard to tell). But I worked around that issue by removing the write protect photo IC sensor, which is identical to the dead one, used that as the index sensor, and used the OLP550 for the write protect.

It can format a disk just fine now, and the new sensor detects the write protect just fine.

3pcedev
August 2nd, 2014, 03:23 AM
Good to hear it worked!

Was the sensor too wide/tall or too thick? If it was just a hair too wide/tall you can probably file a bit off the plastic case.

SomeGuy
August 2nd, 2014, 04:12 AM
It looked like there was room thickness wise. I really couldn't tell beyond that, the board just wouldn't go in. But the write protect sensor didn't have to fit in to anything, just sit on the board.

I've been trying to repair some stuff lately. It is nice when this stuff works, it doesn't always. I just managed to FUBAR what was otherwise a nice little 5x86 motherboard trying to remove a soldered on Dallas battery... :(

andywt
December 3rd, 2018, 09:38 AM
It looked like there was room thickness wise. I really couldn't tell beyond that, the board just wouldn't go in. But the write protect sensor didn't have to fit in to anything, just sit on the board.

I've been trying to repair some stuff lately. It is nice when this stuff works, it doesn't always. I just managed to FUBAR what was otherwise a nice little 5x86 motherboard trying to remove a soldered on Dallas battery... :(


Do you have or know where I can find any documentation regarding the switch setting on the Fujitsu M2551A Controller card?