24 Jul
2016
24 Jul
'16
5:01 a.m.
After successfully repairing the G231 module of the MM11-L set I continued
with the next one. This one was not able to access addresses ending 0100
(binary). Luckily it was not the transistors arrays that were bad but the
selector chip. A Signetics N8251 chip.
I found a source on ebay at $4.95 each plus $13 shipping. A little bit to
much for my taste (although I could make an offer)
Anyone know of a cheaper source? I could use five or ten maybe.
/Mattis
24 Jul
24 Jul
1:13 p.m.
Mattis:
By the description, it is a 1 of 10 decoder chip.
Have you looked to see if it pinout compatable
with a 7442?
Karl
----- Original Message -----
From: "Mattis Lind" <mattislind at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, July 24, 2016 5:01 AM
Subject: Signetics N8251 source?
After successfully repairing the G231 module of the
MM11-L set I continued
with the next one. This one was not able to access addresses ending 0100
(binary). Luckily it was not the transistors arrays that were bad but the
selector chip. A Signetics N8251 chip.
I found a source on ebay at $4.95 each plus $13 shipping. A little bit to
much for my taste (although I could make an offer)
Anyone know of a cheaper source? I could use five or ten maybe.
/Mattis
7:40 p.m.
I have looked at the pinout, it is different, but you can use a method
called "dead-bug"
to wire the 7442 in place of the n8251.
I've attached the spec sheet for the n8251 to this email.
Karl
----- Original Message -----
From: "Karl-Wilhelm Wacker" <kwwacker at ptd.net>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, July 24, 2016 1:13 PM
Subject: Re: Signetics N8251 source?
Mattis:
By the description, it is a 1 of 10 decoder chip.
Have you looked to see if it pinout compatable
with a 7442?
Karl
----- Original Message -----
From: "Mattis Lind" <mattislind at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, July 24, 2016 5:01 AM
Subject: Signetics N8251 source?
After successfully repairing the G231 module of
the MM11-L set I
continued
with the next one. This one was not able to access addresses ending 0100
(binary). Luckily it was not the transistors arrays that were bad but the
selector chip. A Signetics N8251 chip.
I found a source on ebay at $4.95 each plus $13 shipping. A little bit to
much for my taste (although I could make an offer)
Anyone know of a cheaper source? I could use five or ten maybe.
/Mattis
9:12 p.m.
On Sun, Jul 24, 2016 at 5:01 AM, Mattis Lind <mattislind at gmail.com> wrote:
b
After successfully repairing the G231 module of the
MM11-L set I continued
with the next one. This one was not able to access addresses ending 0100
(binary). Luckily it was not the transistors arrays that were bad but the
selector chip. A Signetics N8251 chip.
I suspect that since you've debugged it already, this won't help. Just in
case,
the datasheet is on page 52 of:
https://archive.org/details/bitsavers_signeticsdcs8000SeriesTTLMSI_11847693
/Mattis
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kwwacker＠ptd.net -
mattislind＠gmail.com -
thebri＠gmail.com