28 May
2013
28 May
'13
7:05 p.m.
On 28/05/2013 23:06, Robert Jarratt wrote:
Germanium Transistors are generally leaky. Do you have a multi meter
that will measure gain. You should be able to remote the driver circuit
board and check its gain by prodding into the open connector in the TTY.
would also remove the driver board and check it out on the bench. I
would also be concerned about Q1 on the driver board. If the circuit I
am looking at is like yours Q1 and Q2 and Q2 appear to form a Darlington
pair. If so the main requirement for Q2 will be that it cam sink 500ma.
-----Original
Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 28 May 2013 19:21
To: cctalk at classiccmp.org
Subject: Re: Spec of Motorola 7339 Transistor
related
I am trying to find out some information about
this transistor from my
ASR33 Teletype. Ideally a datasheet to tell me what kind of transistor
it is, and
I am almost certain that 73xx number is the date code. I can't find
any transsitor numbers in any lists.
I haev found my Model 33 schematics. The transistor in question is the
TO3 one on the sub-chassis of the call control unit. It's 'Q2' in the
parts list,
and from the schematic it's PNP. Alas no
equivalent is given, just the
Teletype part number.
Selector, The
even better any information on whether it has a
modern equivalent.
This
page:
http://www.diyaudio.com/forums/parts/167680-vintage-transistors-6.html
suggests it might be a 2N176, but I am not sure. Anyone have any
Well, it's
possible. According to Towers International Transistor 2N176 is in a TO3 can, it is PNP. It's also
germanium, which would go
along
with the measurements you made. On the other hand
the voltage ratings
seem a little on the low side, but...
suspect a
information, old datasheets or anything else that
may help?
I know you've tested this transistor out-of-circuit, but why do you
problem in that area at all? What is the machine
doing wrong?
After my stupidity it started to run open (chatter) in local mode as well as
line mode. But this could simply be because two of the fuses blew. I have
new fuses on order and I hope they will be here soon. It was suggested to me
(and you said it too) that transistors fail faster than fuses and that this
would be an obvious one to test. I thought the voltages I reported to you
were suspicious, didn't you say they indicated it is leaky? I am wondering what my first step should be once I get
the fuses. Just
turning it on would seem a bit risky. I could do the light bulb trick to
limit current perhaps, someone suggested I do this, but disconnect the motor
as it will try to draw too much current.
Regards
Rob
> -tony