Harmonic percolator trannys

suspiciousminds

Next project build is gonna be a harmonic percolator but before i shuffle off to maplins for the parts does anyone know if any of these trannys that i have lying around are suitable to use?
Ac176
2n1671a
Oc44
Oc45
Oc202
Acy44
Acy17
2n388
2n2904a

randomhandclaps

You know the original trannys are Si NPN 2N3565 and a Ge PNP 2N404a.  The silicon you can find plenty of subs for.  Of the germaniums you've got you are looking for one with a range of 50-100.  Probably lower the better.  Leakey germaniums are perfectly fine too and a lot of folks build HPs to use up there low gain leakers - provided after leakage you are getting a Hfe above 50.

EDIT - I just checked some 2N3565s we have in the draw and they all have a Hfe of approx. 300 downwards, so something like a 2N3904 or 2n2222 would be good commonly available subs.  Just remember the 2N2904a you have listed is a PNP so wouldn't be useable in that position.

ecc83

Ho kay...

AC176 tranny radio output device comp' to AC128. Could be useful but probably low hfe and noisy.

2N471 silicon pulse/switching transistor, forget.

OC44/45 MF radio Ge transistiors. Often used in audio in the early days but needed selection for a decent hfe and low noise.

OC202. pnp silicon alloy bit rare? Try it!

ACY44,ACY17 med power drivers, noisy.

2N388  NPN Si  switch forget

2N2904A   -60V PNP 3W power. Forget.

Hope this helps?

Dave.

suspiciousminds

Thanks chaps

suspiciousminds

So, this build went fine - i fitted the correct silicon tranny and the ge 2n404,
Now i also tried the oc45 and it worked quite well too - less gain but a nice bite to it.
I have a spare 4 pole changeover on/on toggle switch (12 lugs underneath).
Is there any way i can use this switch to flick between the two GE trannies?