[GreenKeys] WECo 12H Ge Transistors

Fri Sep 1 09:32:00 EDT 2017

Found a description for a 106C speakerphone

http://www.radiomuseum.org/r/western_el_106a.html which uses the 12H.

where one version used 2N270s

Somewhere in Allentown is going to be an attic will full transistor spec's
:-)

-pete

On Mon, Jul 31, 2017 at 9:21 PM, Justin Scott <tty at impakt.net> wrote:

> 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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