5 Sep
2000
5 Sep
'00
4:29 p.m.
From: Dwight Elvey <elvey(a)hal.com>
Hi
I need some pinouts for some old TTL? or DTL? parts
These are in my computer and I think one of them is
causing a failure. These are all TI parts:
I am especially interested in the
SN15861 and SN15849.
If you can say you are with (or are) a company you can get the datasheets
If you can't and haven't gotten the information email me and I will
get it for you.
David Gesswein
http://www.pdp8.net/ -- Old computers with blinkenlights
5 Sep
5 Sep
5:11 p.m.
Depending on whether you want to maintain just the functionality or the
authenticity of your computer too, you might consider using small GALs to
replace various logic blocks in your circuit. This will impact timing,
making some signals arrive WAY earlier than they might with the OC
DTL/RTL/TTL stuff you've got now. If you've a good sense of how it's done,
you might well be able to make the timing work, however. Back when this
stuff was used, the speeds of today's GALs was unheard of for logic other
than ECL. Logic design techniques were used, which would get one fired
these days, and you never know when you're going to see some of that stuff.
If you have a problem getting a circuit, you CAN build your own in a GAL,
and make the outputs tristate and enabled from their own logic, so they
behave as OC.
Dick
----- Original Message -----
From: David Gesswein <djg(a)drs-esg.com>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, September 05, 2000 7:29 PM
Subject: Re: Need help on old parts??
From: Dwight
Elvey <elvey(a)hal.com>
Hi
I need some pinouts for some old TTL? or DTL? parts
These are in my computer and I think one of them is
causing a failure. These are all TI parts:
I am especially interested in the
SN15861 and SN15849.
If you can say you are with (or are) a company you can get the datasheets
from http://www.freetradezone.com
If you can't and haven't gotten the information email me and I will
get it for you.
David Gesswein
http://www.pdp8.net/ -- Old computers with blinkenlights
11:01 p.m.
Or take the oposite road .............
Build your DTL-gates from discrete components
Few diodes a few resistors and een less small signal
transistors.
I''ve posted the basic diagram on my sit
http://xgistor.ath.cx/files/
Sipke
----- Original Message -----
From: Richard Erlacher <richard(a)idcomm.com>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, September 06, 2000 4:11 AM
Subject: Re: Need help on old parts??
Depending on whether you want to maintain just the
functionality or the
authenticity of your computer too, you might consider using small GALs to
replace various logic blocks in your circuit. This will impact timing,
making some signals arrive WAY earlier than they might with the OC
DTL/RTL/TTL stuff you've got now. If you've a good sense of how it's done,
you might well be able to make the timing work, however. Back when this
stuff was used, the speeds of today's GALs was unheard of for logic other
than ECL. Logic design techniques were used, which would get one fired
these days, and you never know when you're going to see some of that stuff.
If you have a problem getting a circuit, you CAN build your own in a GAL,
and make the outputs tristate and enabled from their own logic, so they
behave as OC.
Dick
----- Original Message -----
From: David Gesswein <djg(a)drs-esg.com>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, September 05, 2000 7:29 PM
Subject: Re: Need help on old parts??
From:
Dwight Elvey <elvey(a)hal.com>
Hi
I need some pinouts for some old TTL? or DTL? parts
These are in my computer and I think one of them is
causing a failure. These are all TI parts:
I am especially interested in the
SN15861 and SN15849.
If you can say you are with (or are) a company you can get the datasheets
from http://www.freetradezone.com
If you can't and haven't gotten the information email me and I will
get it for you.
David Gesswein
http://www.pdp8.net/ -- Old computers with blinkenlights
6 Sep
6 Sep
7:34 a.m.
"Sipke de Wal" <sipke(a)wxs.nl> wrote:
Or take the oposite road .............
Build your DTL-gates from discrete components
Few diodes a few resistors and een less small signal
transistors.
I''ve posted the basic diagram on my sit
http://xgistor.ath.cx/files/
Sipke
Hi All
Thanks for all of the suggestions. I located a 7422
and put that in. My Nicolet is now running like
a new machine again. While it isn't an original DTL,
the date code on the part I used is older than the
other parts on the board. I'm not the type to get excited
about matching original parts. Operation of the machine
is really more important to me. I'll make a note in
my log and if some future owner finds it annoying, he
can put a DTL into it. I have more fun playing with
these old paper tapes and finding out what the software
does.
Dwight
9:26 a.m.
I've corrected an error in the DTL-drawing, the right circuit is
now avaible at the aforementioned site
Sipke
----- Original Message -----
From: Sipke de Wal <sipke(a)wxs.nl>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, September 06, 2000 10:01 AM
Subject: Re: Need help on old parts??
Or take the oposite road .............
Build your DTL-gates from discrete components
Few diodes a few resistors and een less small signal
transistors.
I''ve posted the basic diagram on my sit
http://xgistor.ath.cx/files/
Sipke
9:08 a.m.
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12:15 p.m.
On Wed, 6 Sep 2000, Tony Duell wrote:
Oh come on!. There are places for programmable logic,
but this sure isn't
one of them.
Yes, that's what I think as well.
One of the rules that I work to when repairing a
classic computer is to
replace as little as possible (==keep as much of the original stuff as
possible). So you repair a PCB rather than replacing it. You replace only
the faulty component, not great blocks of logic. Why replace stuff that's
working properly?
In addition, those PALs/GALs will most likely fail before the rest of
the other older components would have failed. It makes no sense to
replace that which is working properly... but then, society has become
conditioned to such lunacy. Look at how many people keep buying new
cars, when the cars they were driving 20 or more years ago would still
be running well had they kept and properly maintained them and not
been susceptible to marketing gimmickry. ...and,over here in the
States, we'd not have become so dependant on "the spying Japanese," to
quote the Dire Straits song "Industrial Disease." (off topic: funniest
thing I've read in a while: a review for a Japanese pickup truck
announced that it towed a horse-trailer loaded with 300-lbs of weight
(no moving horses) up a steep hill... ROFL!)
A PAL/GAL is not going to drop in place of this chip.
For one thing,
there are no known 14 pin PALs. For another, no PAL that I've ever seen
has outputs on the left (like pin 6 of the 7422). So it's going to
involve some kludge-wiring.
Bletch. Is this what the art of repairing things is degenerating into?
Especially as there's a TTL chip (the 7422) that
will drop in place of
the DTL part. The only possible mod would be adding a pull-up from pin 6
and pin 8 to Vcc. Not exactly a big mod.
Yes, true, but it's not modern and wasteful... Could not a great
Monty Python skit be made from this?
--
R. D. Davis "The best way to gain a true understanding of
rdd(a)perqlogic.com Wile E. Coyote on the Roadrunner cartoons is to
http://www.perqlogic.com/rdd fly, head-first, off a horse into something like
410-744-4900 a fence or a tree; trust me, this works." --RDD
8725
days inactive
8726
days old
6 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
djg＠drs-esg.com -
elvey＠hal.com -
rdd＠smart.net -
richard＠idcomm.com -
sipke＠wxs.nl