[GreenKeys] WECo 12H Ge Transistors

[Justin Scott]

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