Re: 5.25 drive destroying boot-blocks

[aw133@lafn.org (James Poore)]

In a previous article, spec@vax2.concordia.ca (Mitchell Spector) says:

>    I have a no-name 5.25 drive (seems to be a clone of the Disk II drive)
>which is not able to boot most disks. After playing with it for a short
>time, I discovered it was actually _destroying_ the boot blocks on any
>ProDOS or DOS 3.3 disk it came across. If you listen, uou can hear it 
>seek over the two tracks or so that it "eats" before going idle. :)
>
>    In anycase, I assume it's a faulty 74xxx chip on the analog board of
>the floppy drive (the controller works okay with one of my Disk II drives).
>I had a quick look inside, all the chips are soldered-in, expect one.
>Unfortunately the 74LS125 is soldered-in, and I would strongly guess this
>is the chip doing the damage. Am I correct, or would it be another? I
>didn't mark down what the one socketed chip is, but I'm sure I could
>salvage a working one to try in the meantime.
>
>Mitchell Spector
>spec@vax2.concordia.ca
>
I have had problems with the 74LS125 on some of my Disk II's.  That chip 
seems to go bad in a lot of situations besides in Apple products.
It probably is just a bad design internally.  Other similar chips dont 
have the same failure rate as the 125's.  TI chips also seem to be the worst.

Jim

-- 
James M (Jim) Poore--Apple II's Forever--Especially IIgs's
Los Angeles Free Net---aw133@lafn.org
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