Messed up tebble booster

[duffrey]

Hey guys,
I'm building Robert Keeley's version of the rangemaster, so it has a negative ground supply.  I'm using one of smallbears tested pnp tranny's and for some reason when I try to bias it, I get around 3V, but to the positive side.  Robert says that it should bias out to a -7.2V.   What's the deal?
Oh, one other thing.  I'm testing from collector to ground, and I assume that the dmm should be hooked up red to collector and black to ground.  Is that right?
Cheers

Jeff

[petemoore]

Yes that's the way to check pin voltages, black to circuit ground.
 As far as running a PNP in a negative ground circuit...
 I would test with a mill tranny till [some old PNP Si ..er something that's easily replaced] till you get 'something'....and can figure out the bias, and debug a little bit, may not sound good but you should at least get some kinda amplification.
 I put trimpots on nealry all the resistors for a Rangemaster transistor candidate testing.
 If you have to stray way off the schematics resistances, the transistor might not be the 'one'...sometimes getting bias on Ge boosters is tricky.
  There have been troubles with using PNP in negative ground circuits...should work in a Pos Gnd. situation.
  The resolution to the PNP in Neg Ground circuitm IIRC was conversion of the circuit to [positive ground.
  II had a Ge Rangemaster transistor purportedly real good, I would make a test board, and fiddle fairly extensively the with Rangemasters components,  then use the 'sacred'  transistor, buy a few extra Ge's wouldn't be out of the question...Si might just sputter for testing...a Ge like NTE 103 or 158 [whatever Ge like that...find a lower gain one]...should be able to find bias on it...
 I've done boards with sockets instead of resistors, plug pots in the sockets...set up bias...take the pots out without disturbing the setting of the shafts, and insert fixed resistors close to the pots measured values into the sockets...or pull the socket...or solder the resistor to the socket on one side etc...