Hi all,
I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.
Thanks
Frank IZ8DWF

On Saturday, 17 November 2018 20:44:14 UTC, wrote:

Hi all,
I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.
Thanks
Frank IZ8DWF

0.8v V_be is odd. Something isn't right there.


NT

On Saturday, 17 November 2018 20:44:14 UTC, wrote:
Hi all,
I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.
Thanks
Frank IZ8DWF

http://pdf1.alldatasheet.com/datashe...CS/ME4101.html


NT

wrote:


I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.


** ME4101 etc devices were made by " Micro Electronics" of the USA - Silicon Valley address.

http://www.microelect.com/

Made a lot of types in TO106 package - shiny, glob tops and gold plated leads.

Very neat looking.


..... Phil

On Sunday, November 18, 2018 at 5:14:51 AM UTC-5, Phil Allison wrote:
wrote:


I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.


** ME4101 etc devices were made by " Micro Electronics" of the USA - Silicon Valley address.

http://www.microelect.com/

Made a lot of types in TO106 package - shiny, glob tops and gold plated leads.

Very neat looking.


.... Phil



You got me curious. Here's a link to a picture. I remember seeing similar transistors years ago in Zenith TVs.

https://www.radiomuseum.org/images/t...n/me4101_1.jpg

Got a bunch in my vintage (70s) AR tuner, receiver & integrated amp (Made by Fairchild per the service manual). I have had to do some pretty substantial rebuilding over the years, but never to those transistors.

Also a few of this type: http://www.gpecsrl.net/img_componenti19/19727.jpg made by Motorola.

Peter Wieck
Melrose Park, PA

wrote:
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.

I removed the suspicious one and put in my curve tracer. Indeed it shows
excessive VCEsat at already 5-10mA, I compared the curve to a bunch of
random BC147/8 that I had around (same era, should be very similar).
The BCs have almost straight saturation line, while this particular ME4101
start to sag towards 0.5V and more already at the 5mA level of Ic.
I'm sure it's marginal even for a 1970's transistor.
I didn't remove another ME4101 but bought a bunch of them (advertised as
NOS), so I'll have fun with the curve tracer once they arrive.

Frank

With such aVBE, they surely are Ge transistors, not Si.

a écritÂ*:
Hi all,
I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).
Now, I'm checking most parts (it's made on 6 PCBs, plus some chassis-mounted
components) for obvious problem, like diode/BJT junctions, carbon composition
resistors values, electrolytic ESR/shorts etc.
All transistor have MAxxxx or MExxxx codes, they really look like BCxxx
transistors from the early 1970's, one of the most common ones is ME4101.
By the way, the ICs have 1972-1974 date codes, so this unit was probably
manufactured in 1974.
My first question is: does anyone have a cross reference for these MA/ME
transistors? Are those a kind of military markings?
Second question: almost all ME4101 have a junction voltage drop around 0.8V
but one of them shows a bit more than 1V drop on both BE and BC junctions
(it's NPN). Can I assume this one must be bad?
Any other hint and information is welcome.
Thanks
Frank IZ8DWF

Look165 wrote:
With such aVBE, they surely are Ge transistors, not Si.

They are all Si transistors. Ge have Vbe around 0.3 to 0.4V, I have quite
a few devices with Ge transistors.

Frank

On Friday, 23 November 2018 08:28:18 UTC, wrote:
Look165 wrote:

With such aVBE, they surely are Ge transistors, not Si.

They are all Si transistors. Ge have Vbe around 0.3 to 0.4V, I have quite
a few devices with Ge transistors.

Frank

I can't imagine what Si tr would have 0.8v V_be or why. Do you know?

Geraniums start much lower of course, but also rise higher quickly as current increases. 0.8v on a Ge junction is no cause for surprise.

The ME tr you mentioned is a Si device, so I'm puzzled by its V_be.


NT

wrote:

I can't imagine what Si tr would have 0.8v V_be or why. Do you know?

a faulty/degraded one, that's why I decided to substitute this one.
The other have all less than 0.8V VBE, my first measure was actually
not correct. Only one measure 0.8V and I also verified that it has
an incorrect behaviour with the curve tracer.


Geraniums start much lower of course, but also rise higher quickly as
current increases. 0.8v on a Ge junction is no cause for surprise.

The ME tr you mentioned is a Si device, so I'm puzzled by its V_be.

degraded junctions maybe, degraded material, doping migration, who knows.

I have a few samples of "interesting" semiconductor faults, this one is
definitely one of them.
Another notable one I've found years ago is a 2W zener diode showing 0.7V
zener voltage and 0.2V forward voltage. Both ways with very soft knees,
it was about to short probably. Interestingly, it was new, never soldered
in.
Frank

wrote:
Hi all,
I'm restoring a couple of 1970's wooden case acoustic coupler, both made in
the UK.
I haven't find the slightest bit of information about both of them, just
some pictures on the net.
One of them is the DCD model AC.350.OM (where probably OM stands for
Originate, as it doesn't have any Orig/Answ switch).

If anyone is interested, I produced a few video from all the repair
process of this 1974's acoustic coupler:

https://www.youtube.com/watch?v=ZAICCy4OC-8
https://www.youtube.com/watch?v=4-StGVDZzXA
https://www.youtube.com/watch?v=V3nH4li8MjA

Frank IZ8DWF