Weird biasing problem with my Rangemaster clone

Started by mordechai, December 12, 2016, 11:28:01 PM

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mordechai

So...I have a very nice CV7355 PNP transistor in my Rangemaster clone.  It's got an HFe of about 108 with low gain (.06ma), so it's right in the proper range for use in this circuit.  I'm using the normal resistor values for the most part with a 68K from the base to GND, and a 5K trimmer on the emitter to GND.  And for some reason -- with fresh 9V battery -- I can't get the voltage on the collector to get up past about 4.45.  I lowered the 68K to a 56K and got it to about 5.15V, but not higher than that. 

EDIT -- nevermind.  Simple error on my part in doing the readings, and now it's working great.  Damn, try those CV7355's in this circuit, they're amazing.

antonis

Quote from: mordechai on December 12, 2016, 11:28:01 PM
EDIT -- nevermind.
It DOES mind...!!!  :icon_evil:

I was ready to tell you that even if you used the 68k resistor from Base to GND it still needs a 470k from Base to -9V for a proper bias..

But now you've made the above statement useless and I came with a more worn keyboard for nothing...  :icon_lol:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..