[GreenKeys] WECo 12H Ge Transistors

[Pete Lancashire]

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
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
>
> 2002-to-present greenkeys archive: http://mailman.qth.net/
> pipermail/greenkeys/
> 1998-to-2001 greenkeys archive: http://mailman.qth.net/
> archive/greenkeys/greenkeys.html
> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
> http://comcents.com/tty/greenkeyssearch.html
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20170731/f2348109/attachment.html>