The Tek P/N 155-0015-01 is a TTL BCD-to-Decimal
converter. My cross reference doesn't say exactly
which one, but it is probably a 7441, 7442, or 7445.
The 155-0038-01 is a 16 pin D/A TTL converter. No
other info.
Craig: The 7454 is obsolete but is still available
from surplus dealers for about $1 US.
Jim Reese
--- Miroslav Pokorni <mpokorni2000@...> wrote:
Hello Craig,
You might want to consider using a wire-OR of
2-input open collector NANDs,
e.g. 74LS38. It is still a kludge but it is only one
IC with few wires and a
flying resistor. If you place a socket on the
circuit board and use one of
those 'discrete component adapters' you can do whole
thing without cutting
original board.
While on the subject of strange ICs, does anyone
know what are Tek's
155-0015-01 and 155-0038-01; the latter is used in
7M13, a Readout Unit, a
plug in that puts text on the screen of 7000 scope.
Regards
Miroslav Pokorni
----- Original Message -----
From: "Craig Sawyers"
<c.sawyers@...>
To: <TekScopes@...>
Sent: Thursday, January 24, 2002 12:39 AM
Subject: [TekScopes] HP counter - off topic
Hi List
I *know* this is a Tek list - so this is off
topic. However, I was so
pleased to have sorted out a problem on my HP
5328A timer I just had to
crow
a little.
Ever since I got it, some of the funtions didn't
work well (like time
interval and ratio). However, when frequency and
period measurement died
too it was clearly time to do something about it.
Now this counter cost
me
?22 (around $30) on eBay, so it owed me nothing -
but I'm a determined
cuss
and rarely admit defeat.
Followed around 3 days of diagnostics - derailed
by errors in the manual
(the military version). Eventually it turned out
to be a chip on the
Function Selector card - labelled Time Base
Multiplexer. Now this was a
7454, now obsolete. So having dug out the chip,
isolated the output pin
and
confirmed that it was indeed *that* chip (and not
the one it was driving
holding its output low) I was then confronted with
what to do.
Now the chip is a bunch of ANDs and a NOR that
does /(AB + CD + EF + GH).
So it would have been possible to replace it with
a 7400 and a 4-input
NOR -
except that there is no 4-input NOR in fast TTL,
just in slow CMOS (and
this
chip has to handle a PLL synthesised 100MHz
clock). So I transformed the
logic funtion to /(AB)./(CD)./(EF)./GH and used a
74F00 (quad 2-input
NAND)
and 74ALS21 (dual 4-input AND), strung together in
place of the original
7454.
Works an absolute treat!
Cheers
Craig
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