Hello from Kozhikode...India

[sivan_and]

Hello am from Kozhikode...India
My profession and hobby r same Electronics....Most of the electronic items in our home are diy..Am a great DIYer

[EC8010]

Welcome to the forum. So what do you make? Electronics? Loudspeakers? Everything?

[sivan_and]

I like to build things alll by myself...been a DIY hobbyist since past 25 years, I build Audio systems the first amplifier was transisterized 2+2 Watts in AC187/ AC188 germanium transisters , amplifying ceramic cartridge pickup.
Then i made TBA810 chip in 1984 years ago.....

[EC8010]

Gosh, I remember blowing up germanium transistors (AD161/AD162 and AC128)!

[sivan_and]

But that was not the first,I remember i made a super simple Mediumwave radio. a germanium diode OA79 in series with an old telephone earpiece one end of it was connected to water pipe(Superb earth)and other end to an antenna.

Thermal runaway...i too had this problem...
AC128, i remember in a transisitor radio,kit,called "Jetking" i made
when i was in School.Unfortunately it didn't work first time.i wrongly placed a transistor,since the package was different from the manuel.that was BF495.I took it to a radio shop for repair, the guy made me a laughing stock and warned my Father no to encourage this kid into such hobby....

[EC8010]

My germaniums fell victim to the soldering iron which was heated by putting it on the stove. It was a little while before I could afford an electrically heated iron, and a long while before I bought a thermostatically controlled iron.

[aman]

hi sivan,
I m from delhi and i too a diyer from 1990 and have built many audio amplifier using ic and transistors. At present i have got a problem . I own an old woodstock amplifier using to-3 germanium power transistor without any no/name on them and transistors of one channel has been blow up dut to shorted output and i m unable to find their replacement as there is no number on them so that i could find their replacement. The amp works on 0-40 volts and the output transistors are pnp. Please provide me the necessary help.
Aman

[sivan_and]

It may be PT4 or AD149 (no sure abt PNP) ...will check when i get back home...

[aman]

hi sivan
you r right my friend i also own another old amplifier which uses pt 4 and pt6 in the output but they are all bown up due to my slight mistake and i now that amp is lying in my junk. i also think AD149 is an equivalent of PT6 and both of them are pnp as i have seen specs of AD149 in my transistor equivalent book. But i wanna use modern silicon power transistor (mj2955) and i have read that the biasing must be changed according to the new silicon transistor but i donno how to do this, please help me coz I have got no backgroud of physics i have done MA(economics) but i m interested in building power amps. I can build amp only if i have got right schematic but i cannot modify any amp.
Aman

[sivan_and]

Its not worth all the trouble to modify germanium with silicon transistors..afterall 2N3005 trans are not purely meant for audio..
I have a couple of AD149 and PT4,PT6 ..will let you know later....