Subject: DTL chips? 74H... chips?

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: 18 Jan 1994 16:25:28 GMT

I've acquired a fair collection of PC boards from random old hardware,
and recently, I've been trying to reduce its size by pulling chips and
throwing out the old fiberglass.  I've got a few hundred 1970 to 1975
chips salvaged at this point, about 20% DTL, 30% 74H... and 50% regular
TTL, and a fair stock of Signetics 8T series chips.  It's a brainless
thing to do, I admit, but when it's 20 below zero outside, a warm
soldering iron (with DIP de-soldering head) is nice company.

So, I suppose my next little job will be to start testing the darned
things.  If I get a 50% yield on chips that are no-longer in production,
I'll be content.

Should I even bother with recovering DTL chips?  At first, I skipped
them, but then I went back and pulled a pile of them just on
speculation (long cold days do that to people, I guess).

					Doug Jones
					[email-masked]

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From: [email-masked] (PDP11 Hacker .....)
Date: Tue, 18 Jan 1994 18:46:00 GMT

In article <[email-masked]>, [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879) writes...
>throwing out the old fiberglass.  I've got a few hundred 1970 to 1975

I only do that if I can't identify the board, or it's physically damaged, or I
_know_ I'll never get the hardware it fits. Otherwise it gets labeled and put
in my box_of_spares_for_stuff_I_might_get_one_day, which currently contains a
lot of demountable disk spares and (OBpdp8) a load of R,S,B series boards for a
straight-8, amongst other things.

>soldering iron (with DIP de-soldering head) is nice company.

I prefer the solder-sucker myself, and have a pretty good record of separating
the board from the chip and leaving both intact.

>speculation (long cold days do that to people, I guess).

If it were me, I'd pull the DTL, and leave the 74xxx. I can normally find a
modern replacement for TTL (I don't insist on historical accuracy - I'll quite
happily pop a 74F00 in the place of a 74S00 for example), but DTL is difficult
to find replacements for. If the wire-AND feature is not being used, then TTL
will work, and if it is, the equivalent O/C TTL will work with a 3k (ish)
pull-up. BUT, what do you do when a DTL flip-flop has wired-and outputs? In
some cases, pulling the output of such a device low can change the state of the
flip-flop, and I've seen this feature used in a commercial device.
So, I'd keep the DTL as well.

>					[email-masked]

-tony

Bristol University takes no responsibility for the views expressed in this
posting. They are the personal views of the user concerned.

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From: [email-masked] (Charles Lasner)
Date: 19 Jan 1994 12:44:27 GMT

In article <[email-masked]>,
>speculation (long cold days do that to people, I guess).

Two things:

1)	If the DTL chips are spares for the W707, etc. modules of the
PT08, please make them available.  Some of us have repairable boards for
the peripheral which don't work "for the want of a nail" of repairing some
of those boards *all* of which are DTL.

2)	This raises the issue of what spare chips we all need to support
some of the 8/e boards.  Unfortunately, DEC used some chips that were
never all that popular, and while we can more easily get older stuff, what
do you do for certain specific ones?

In any case, I think we should start compiling lists of chips that aren't
74xx and give references to their frequency of usage, i.e., there are
Omnibus boards that use 1-3 SP314 chips as the device decoder, etc.  And
also, the boards need to be "weighted" in terms of both how many are
likely to be needed to be supported.  (It's reasonable to expect 3 KL-type
boards per reasonablly-configured -8/e, so their funny-chip-usage counts
should be multiplied by 3, while funny-chips from say the DP8E synchronous
modem interface shouldn't "count" as much, etc.)

Then hopefully we can get a handle on just what our potential requirements
are, as well as potential sources for the chips themselves, etc.

cjl

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From: [email-masked] (krause)
Date: Fri, 21 Jan 1994 09:17:05 GMT

>speculation (long cold days do that to people, I guess).

Certainly you should!
You can (still) buy TTL-chips, but you can't buy DTL-chips.
A similar problem is with the old japanase PMOS-chips, for example HD 31xx
and HD 32xx or uPD 10 and so.
They are very often in old desktop calculators and Hitachi and NEC even don't
remember that they ever built such things.

So put them on stock.

Klemens Krause
University Stuttgart
(germany)

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From: [email-masked] (PDP11 Hacker .....)
Date: Fri, 21 Jan 1994 09:54:00 GMT

In article <[email-masked]>, [email-masked] (krause) writes...

>and HD 32xx or uPD 10 and so.

Are those the ones that stuff the boards in (say) the Casio AL2000?
If so, does anyone have pinouts/data/etc for them. I've got some machines using
them that I am trying to repair at the moment.

-tony

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From: [email-masked] (krause)
Date: Mon, 24 Jan 1994 09:42:03 GMT

>them that I am trying to repair at the moment.
I have the pinouts and short functional description of some of them. 
HD 31.. was high voltage PMOS (-27V) and HD 32.. was low voltage PMOS (-17V) or
so. Most of them was SSI, but there is also a BCD-ALU and shift registers.
I can post my information here on the net, but I don't know, if this here is
the right group (.PDP8)?

I once analyzed the Casio AS/L, a small desk top calculator with those IC's from
1970. It's highly interesting, he has something like microprogrammed CPU below
the i 4004. The whole microprogramm consists of 256 words with 16 Bits, where
8 bits contain the adress of the next word. Conditional jumps are made by an
AND which is connected to the carry output of the CPU and which masks out an
address line of the microprogramm ROM.
The 256 words of microprogramm perform floating point and fix point arithmetic
as well as one calculating memory register.

Klemens Krause
University Stuttgart
(Germany)