Disk ][ issues

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Disk ][ issues

Hello all,

Some time ago, I acquired an Apple ][+ with a disk interface card and two drives. I just recently got the ][+ working after determining that one of the chips in the first 16K of RAM was bad. To do that, I had to pull a chip from my language card, so I currently only have 48K until my RAM arrives tomorrow.

After getting the computer up, I connected the drives to the interface card and put it in Slot #6. Turned it on and the drive just spins. When I use my //c to send a disk using ADTPro and try it in the ][+, the disk ends up being erased. I read a forum post that said that this is probably a bad 74ls125. I have ordered some from eBay, but are there other possible issues as well?

I know that I did not plug the cable in wrong, but I can't speak to what the previous owner did. Based on the corrosion that I found on some of the pins of the chips, I would say that it was not stored well. I jsut want to get it up as soon as possible as I am new to the old Apple computers. (I grew up with Commodores and only used Apples at school.)

Thanks!

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Re: Disk ][ issues
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Re: Disk ][ issues

Thanks SpeedyG!

Based upon that information, I have also ordered a CA3146E and MC3470P for each drive. Should I replace all at once or one at a time? Is there any danger of blowing the new ones if the old ones are bad and not replaced?

Also, my analog board does not match either of the ones pictured on your page. You show a 600-0037 and a 650-0103, but I have a 600-0038. Would you like pictures to add to your page?

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Re: Disk ][ issues

Hello jdunlap,
to answer your question:
The problem is explained in the text. Between killing of a chip by another damaged chip time is in worst case scenario
rather short > firsst death ( 74LS125 )within 5 to 10 seconds, second chip( CA3146 ) several seconds later within next 10 to 25 seconds and final damage at third chip( MC 3470 )probably after 2 to 3 minutes.

Regular bootup time from disk is approximatly 30 to 60 seconds. So 74LS125 and CA3146 should be changed in same time. If the drive boots up within normal time ( 30 to 60 seconds ) and is reading and stepping the MC 3470 may stay in place and only gets replaced if speed- and track adjustment fails and sill a bunch of read errors remain ( generaly with bad comment from DOS or ProDOS ).

Yes Pictures are welcome, but i do not publish my email adress here in public space. But if I get a PM here i will reply also with PM and email edress.

SpeedyG

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Re: Disk ][ issues

After replacing the 74LS125, the 3146, and the ULN2003 (I had some extras around) and using Locksmith to adjust the speed, I am now able to consistently boot from one of my drives. The other still isn't working, but now that I have one working, it's just a matter of time for the other. I am still waiting on the other chips to come in. Also discovered three additional bad RAM chips through my own tests and a fourth on the language card using the Diagnostic II+ disk. Now, though, I am able to boot ProDOS without the relocation/configuration error!

I uploaded the pictures to Dropbox, and here are the links

Image #1
Image #2

Sorry, I couldn't figure out how to put the images inline.

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Re: Disk ][ issues

In vary rae cases if Drive 2 refuses to operate correct and neither speed sdjustment nor
track alignment will work due to having none access to Drive 2 the trouble might be located at
the interface.....

In such very rare cases the 3 red marked chips be the source of the trouble
disabeling to generate drive selection signal

SpeedyG

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Joined: Jul 14 2018 - 12:54
Try swapping the drives.

Try swapping the drives. Drive 1 plugged to the bottom, and Drive 2 to the top of your interface card. Then try and boot from Drive 2. If it works, then the problem is the interface card, if not then the problem is the drive. If it is the drive, then swap the analog cards between the two drives, and try booting again (do not replace the casing). If that works, then you can start swapping chips between the working, and non working cards to isolate the failed component. If the problem persists, start looking at the mechanics. This was the procedure I used to fix my Drive 2 on my //e.

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