[GreenKeys] WECo 12H Ge Transistors

Tue Aug 1 00:21:02 EDT 2017

Pete,

I figured that might be the answer.  I suspect I could bias some Si BJTs correctly in some cases, or possibly adapt the circuit to self-bias the Si BJT... but I don't have a firm enough grasp on exactly how the 101C works yet to even contemplate it.

I have *some* docs, which came with this machine, but it seems to be lacking quite a lot of the 101C wiring/schematic diagrams, which are what I probably need most.

Thankfully, at least in the case of this 35 ASR, the issues all were in the timer card and send break timer card, and those were relatively easy to repair - one resistor was out of spec, may or may not have had much to do with my troubles, but I found that before digging into the transistors.  Of course the Send Break Timer has several other types (12F, 12G, some 8's) but not enough for me to get a good sample set with my equipment to determine which were good or bad, so I just focused on the 12H's.  Replacing the bad and questionable ones on those two cards solved my initial line seizure timing/answer carrier detection timing and spontaneous break/blind conditions I faced.

I ended up having so much fun with the machine this evening that I ran its ribbon dry, and put on a fresh replacement. :)

Here's the machine itself:
http://i.imgur.com/NxYjvXi.jpg

And a close up of some copy from calling various things in the house with it (through a terminal server that did the baud and stop bit conversions for me):
http://i.imgur.com/txxad5j.jpg

It could probably use a few more slight adjustments and tweaks, but it's running quite serviceably now!

cheers,
dj

Pete Lancashire(pete) wrote:
> Can't help you, but nice to see someone else with 101-C's I have one in a
> KSR35 and one that goes in a ASR33 but the 101-C was unmounted from the 33
> and put back into the pedestal w/o protecting the 50 pin connectors.
> 
> The hard part is getting Ge transistors not only match a 12H but still
> work. Another hobby I have is fixing early AM transistor radios and the
> last batch of Ge's were ex Soviet's via eBay.
> 
> The spec's for the 12H are on page 51 of ...
> 
> http://doc.telephonecollectors.info/dm/WEco_Solid_State_Devices_ocr_r.pdf
> 
> And since just about any transistor you find as a substitute will have a Ft
> much higher then 12H's of 2.4 Mc (hey its old), have a batch of ferrite
> bead on hand
> 
> -pete
> 
> 
> 
> 
> 
> On Mon, Jul 31, 2017 at 9:06 AM, Justin Scott <tty at impakt.net> wrote:
> 
> > Is there anyone out there with a bucket of WECo 12H Transistors or does
> > anyone know a viable equivalent?
> >
> > I'm in the process of restoring a pair of Data Set 101C's, and between the
> > two, both have a number of these old germanium units that are either
> > completely shot, or have gone so far out of spec that their circuits no
> > longer function as expected.
> >
> > I'm not looking forward to understanding all these circuits well enough to
> > figure out what I need to do to bias a silicon transistor in each position
> > to make it behave with a circuit expecting a Germanium unit.
> >
> > Between my two datasets, I've managed to test out enough working in-spec
> > 12H's to make the dataset in the 35 ASR work, so I'm very happy to report
> > that my 35 ASR is back on the air for the first time in
> > who-knows-how-long.  The one for my early 33 ASR is now missing a large
> > number of 12H's since I've already found at least 3-4 that are completely
> > shot, and at least as many that are completely out of spec on gain and
> > currents.
> >
> > My end goal is to get both datasets working in time for a show in a couple
> > months, as I'd like to use
> > both units for calling into a host computer over a phone switch.
> >
> > For anyone doing this kind of work, I cannot praise highly enough the PEAK
> > Atlas DCA Pro (I have no interest in their outfit, so this is completely an
> > unsolicited endorsement).
> >
> > As seen here: http://i.imgur.com/BhpNZHs.png
> > The Ic/Vce curves of the bad units are easily discernable - each of those
> > that took a hockey-stick curve upward early in the collector-emitter
> > voltage scale all reported the same hFE on my multimeter as the ones that
> > had in-spec curves on this scale.
> >
> > Likewise, as seen here: http://i.imgur.com/fzDW4fs.png
> > The hFE/Vce curves of several units are quite easily identifiable.
> >
> > Without this tool, it would have been painful to try and figure out which
> > transistors were bad.  The ones that immediately report higher hFE than the
> > majority are easily identifiable on their own... but the ones with a basic
> > hFE test that matches the range of the spec but then crash at higher
> > voltages or currents would have been maddening to figure out. :)
> >
> > cheers,
> > dj
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