Apple //e no power when Disk ][ drives are attached

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Apple //e no power when Disk ][ drives are attached

Hello friends! I figure it's about time I created an account on this site given how long I've used Apple computers. 

I just took my non-enhanced Apple //e out of storage yesterday and spent several hours using it successfully. Today it would not power on (no beep, no LEDs). I isolated the problem to the Disk ][ drives: when both are disconnected from the Disk ][ controller card, the computer starts normally. 

Next I wanted to figure out whether the problem was just one drive or the controller card. Since I believe the drives are interchangeable, and because I didn't know if the controller would work with a drive connected only to drive connector 2, as a first step I decided to plug the drive 2 cable into the card's drive 1 connector. This resulted in a flickering Apple //e power LED and an unhappy crackling sound from inside drive 2. I opened drive 2 and don't see any obviously burnt components. 

I'm now undecided about what to do next. I'm concerned that I've fried drive 2 and that (if the problem is the controller card) if I connect drive 1 I'll fry it as well. Any suggestions?

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Sounds like you've got a

Sounds like you've got a short somewhere, or your power supply may be going bad.

 

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You're correct that the

You're correct that the drives are interchangable, and that the card won't recognize a drive attatched to connector 2 without Drive 1 being present.  To isolate if the issue is the drive, computer, or card, you will need to test Drive 1 without Drive 2.  If the malfunction persists, then it's something on either the card or board. If not then the issue is drive 2.  

 

If it is the drive, You can swap the analog cards inside the drive to see if the issue follows the card.  From there, swap the chips between the cards to isolate the damaged component.

 

Another thing to considder is the slot that the card is incerted into.  A disk controller is typically installed in slot 6, but can work in slots 5 and 7 as well.  Dirt, debris, or corrosion on the slot can cous malfunctions as well.  Usually cleaning the slot remedies this, but it's possible that short in the slot could have damaged the drive.

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Disk ][ Analog card issues

Disk ][ Analog card issues are most often the 74LS125.

 

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It's drive 2

Thanks for the suggestions.

I had already tried putting the disk controller card into slot 5 instead of 6, which didn't change the problem. The computer is quite dirt and corrosion free. It's been in my possession since the late 80's when I got it second-hand but it got a new revision B logic board after that and it's mostly been in storage since the 90s.

I also opened the power supply and everything looks clean and intact in there too so I'm not changing anything there for now. I know the Rifa capacitor might asplode someday but I'll deal with that then.

I decided to be brave and connect just drive 1 to the card's drive 1 connector (drive 2 not connected) and it worked fine for hours, so I assume the problem is in drive 2. When I feel adventurous, I'll try connecting drive 2 again and swapping parts between the drives to identify the bad component.

The 74LS125 on drive 2 looks intact, but there is a little black goo, perhaps melted plastic, on some of the pins that is not present on the 74LS125 on drive 1. Maybe the chip was beginning to melt when I turned off the power. Maybe it will melt further if I connect it again. Maybe I'll put the computer outside when I do that in case it smells. Interesting (or probably not), the two drives have different 74LS125 chips with different manufacturer logos on them. The bad drive 2 has SN74LS125AN with a Motorola logo while the good drive 1 has DM74LS125AN with a logo composed of two wavy lines which I don't recognize.
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ryandesign wrote:Thanks for
ryandesign wrote:

Thanks for the suggestions.

The 74LS125 on drive 2 looks intact, but there is a little black goo, perhaps melted plastic, on some of the pins that is not present on the 74LS125 on drive 1. Maybe the chip was beginning to melt when I turned off the power. Maybe it will melt further if I connect it again. Maybe I'll put the computer outside when I do that in case it smells. Interesting (or probably not), the two drives have different 74LS125 chips with different manufacturer logos on them. The bad drive 2 has SN74LS125AN with a Motorola logo while the good drive 1 has DM74LS125AN with a logo composed of two wavy lines which I don't recognize.

 

The manufacturer of the 74LS125 is unimportant.

Replace them both and see if that fixes the problem.  They're cheap.

 

 

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