Duodisk and Unidisk Drives Red Light Constantly Stays On

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Duodisk and Unidisk Drives Red Light Constantly Stays On

Hello,

I am new to this forum and I have had issues with two disk drives that I have. They are doing the same thing. The first one is duodisk drive and the second one is a unidisk drive. No matter what Floppy I put in either drive the Red Light just stays on and the disk drives just spin. These are things I have tried. See below:

1. Tried different typed of disks (Originals and Copies - No Change For Both Drives)

2. Tried Two different controllers (No Change For Both Drives)

3. Tried a known working controller on a working machine (No Change For Both Drives)

4. Tried a known working duodisk drive on all the controllers ( They all worked fine)

5. Cleaned both drives really thourough (No Change For Both Drives)

6. Made sure all drives were in operational conditional.

I am narrowing it down to a board issue on each drive. What is the actual chip on the boards that would be the issue? I was wondering if someone has any suggestions or ideas. Thank you in advance.

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The disk has nothing to do

The disk has nothing to do with it. Doesn't even matter if you insert any disk or the drive is empty. The controller simply selects/enables the drive - this turns on the motor and the LED. This is controlled by a a simple, separate signal in the connector cable.

If you already ruled out a defective disk controller card, then it's either a bad cable or disk connector - or an issue on the motor driver board (screwed to to the back of the drive, if I remember correctly).

 

https://embeddedmicro.weebly.com/apple--disk-drive-schematics.html

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You said that you had cleaned

You said that you had cleaned both drives but did you clean the drive heads themselves with isoprophyl alcohol?

Is the felt pad in good shape and pressing the disk tightly against the drive head?

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MacFly wrote:The disk has
MacFly wrote:

The disk has nothing to do with it. Doesn't even matter if you insert any disk or the drive is empty. The controller simply selects/enables the drive - this turns on the motor and the LED. This is controlled by a a simple, separate signal in the connector cable.

If you already ruled out a defective disk controller card, then it's either a bad cable or disk connector - or an issue on the m

 

Yes that is what I was referring too. The motor main board. The controllers are all fine and working with other drives. So I am trying to figure out what on the drive board could go bad.  What do you mean by bad disk connector? I already tried another cable with the same result on another 2e that I have.

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Wayne wrote:You said that you
Wayne wrote:

You said that you had cleaned both drives but did you clean the drive heads themselves with isoprophyl alcohol?

Is the felt pad in good shape and pressing the disk tightly against the drive head?

 

 Yes I cleaned the heads with isoprophyl alcohol thouroughly which is what has been included in the cleaning. The felt pad looks great and tight.

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For the duodisk have a look

For the duodisk have a look in the service manual: https://ia801601.us.archive.org/32/items/ATP_87/ATP_DUODISK.pdf

There is also a table with likely chips causing certain symptoms. There is also a list for the symptom "motor/LED always on" - see page 13. I would start with the 74LS125 - this makes a lot of sense, according to the schematics. Also, it's directly connected to the interface cable, so could easily get damaged when plugged to a defective interface card (or when the cable was incorrectly connected). The suggested CA3141 may be more tricky to find. But this chip only contains a bunch of diodes, so you could easily verify if these were still ok (using the datasheet and a multimeter).

I don't have a 3.5" unidisk. If I see that correctly in the schematics, then Apple did design an own chip for the unidisk, which integrates almost all of the logic. You might be out of luck there (unless you can find a donor).

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MacFly wrote:For the duodisk
MacFly wrote:

For the duodisk have a look in the service manual: https://ia801601.us.archive.org/32/items/ATP_87/ATP_DUODISK.pdf

There is also a table with likely chips causing certain symptoms. There is also a list for the symptom "motor/LED always on" - see page 13. I would start with the 74LS125 - this makes a lot of sense

Well on the Unidisk drive I will put that one to the side for now. Since we are talking about the Duodisk drive I have used this manual before and it is funny. but I did not find any useful information until you just made some sense of it. I have tried two different cables and one that I knew worked and it did the same thing as I plugged it into a known working computer with cable. I have one working Duodisk drive so I know the cables are good, but I will now look at the board now and let you know what I find out.  Did you happen to know the voltage  draws on this 74LS125 chip? I am not able to find them in the manual. Thank you.

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i have the same issue in my

i have the same issue in my duodisk, but it is intermittent.   I can't figure out what the issue is.   Sometimes it works, for a while, like for a few hours, then is dead until the next morning. I checked the cabling. i tried two different controller cards and two different cables.  Same result, wondering what else to check?

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fegos wrote:i have the same
fegos wrote:

i have the same issue in my duodisk, but it is intermittent.   I can't figure out what the issue is.   Sometimes it works, for a while, like for a few hours, then is dead until the next morning. I checked the cabling. i tried two different controller cards and two different cables.  Same result, wondering what else to check?

 

Not trying to be mean here, but you are hijacking my thread.

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mbc230 wrote:MacFly wrote:For
mbc230 wrote:
MacFly wrote:

For the duodisk have a look in the service manual: https://ia801601.us.archive.org/32/items/ATP_87/ATP_DUODISK.pdf

There is also a table with likely chips causing certain symptoms. There is also a list for the symptom "motor/LED always on" - see page 13. I would start wi

 

So an update I checked the board and it is 676-0107-B so I am guessing it is a bit newer then the ones referenced in the service manual.....Do you happen to know who sells the replacement chips? Thank you.

 

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sorry not intented

i had similar symptoms. found that it was the wiring from the head to the analog board.     I also have that board revision you mentioned.   Also i have a spare analog board if you are interested DM me.

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fegos wrote:i had similar
fegos wrote:

i had similar symptoms. found that it was the wiring from the head to the analog board.     I also have that board revision you mentioned.   Also i have a spare analog board if you are interested DM me.

No Worries and PM Sent. Thank you!

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