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ME/MA UK 1970's transistors?

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

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

NT

Reply to
tabbypurr

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NT

Reply to
tabbypurr

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

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

Very neat looking.

.... Phil

Reply to
Phil Allison

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

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Reply to
John-Del

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:

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made by Motorola.

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

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

Reply to
frank

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

Reply to
Look165

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

Frank

Reply to
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

Reply to
tabbypurr

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.

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

Reply to
frank

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

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Frank IZ8DWF

Reply to
frank

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