Iomec disc drive ?

From: Jay Jaeger <>
Date: Sat Jan 3 08:45:03 2004

Actually, at least some of them (9094 JK flip flops) are indeed DTL. Some
are closer to TTL. None of them seem to involve uncommitted emitters,
though some of them appear to be fairly standard uncommitted *collectors*
(and in at least once case involve the use of wired-or, which means I would
have to use an open collector TTL part if I had to replace it, perhaps also
requiring a pull-up somewhere).

Some of them (e.g. 9097) are apparently CTL, but I don't know that there is
a lot of that there, and the board I am most likely having problems with
appears to be all CCSL.

The family termed CCSL by Fairchild - Compatible Current Sinking Logic -
seem to be largely compatible with TTL, within source/link limitations,
though pinouts are likely to be different, and therefore a possible problem


At 06:49 PM 12/31/2003 -0500, Bob Shannon wrote:
>Those are NOT DTL chips!
>Your looking at CTL logic, which uses a circuit similar to an uncommited
>emitter output rather than the
>conventional totem-ploe output stage.
>There are no drop-in replacements, and you cannot use DTL or TTL parts.
>Jay Jaeger wrote:
>>I have one I am working on -- attached to an HP 2114. The drive spins up
>>and can seek. The interface cards in the CPU pass their diagnostics, but
>>the controller is locking up -- looks like a problem in the state flip
>>flops that control the early part of a command.
>>Also, my guess is that this one is 1.2MB, not 2.5MB. It has one fixed
>>platter and one removable platter. It also is exhibiting head/disk
>>interference ("ting") on unload, but so far doesn't seem to be damaging
>>anything when it does it (but I am using junk pack, just in case -- can't
>>tell if the ting is coming from the fixed or removable platter).
>>If you want to recover the data, you might consider putting the platter
>>into an RK05, doing an a/d and capture of the raw data (or even the bit
>>stream after recovery) from the pack. Might be safer.
>>The logic in my IOMEC 1802 controller that is unhappy has Fairchild chips
>>-- not standard 74xx fare. It may well be that they are DTL (sample
>>markings on one are DT uL909759 7020), which I am currently guessing is a
>>9097 chip.
>>Jay Jaeger
>>At 11:11 AM 8/26/2003 -0500, Tom Uban wrote:
>>>Is there any chance that someone has an Iomec removable platter
>>>disk drive? The type that I am looking for uses an IBM 2315 style
>>>2.5Mb cartridge, similar to an RK05.
>>>I know that this is a pretty futile request, but it never hurts
>>>to ask...
>>Jay R. Jaeger The Computer Collection

Jay R. Jaeger The Computer Collection
Received on Sat Jan 03 2004 - 08:45:03 GMT

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