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Setting Bias [message #15096] Thu, 13 January 2011 21:03   cassent5150 Messages: 341 Registered: August 2009 Senior Member I'm needing info on setting the bias on these output transistors I replaced in my Kustom Amp. Steve C Steve C Report message to a moderator

Re: Setting Bias [message #15099 is a reply to message #15096] Fri, 14 January 2011 12:51 chicagobill Messages: 2005 Registered: April 2003 Senior Member I'm not sure that I understand what you are trying to find out here. Somewhere we were discussing the replacement of the original Germanium output transistors with new modern Silicon types. But then I thought that you were replacing the original ones with NOS ones, which would not require a bias change. But here's the general theory. Germanium transistors will conduct or "turn on" with less voltage than Silicon ones. The original design set up the output transistors with maybe 0.3 vdc on the bases, which is enough for a Germanium type to work. A Silicon transistor needs more like 0.6 vdc to turn on, so you need to change the resistors that feed the voltage to the bases of the outputs to get the base voltage up to 0.6 vdc. Report message to a moderator

Re: Setting Bias [message #15102 is a reply to message #15099] Fri, 14 January 2011 21:41   cassent5150 Messages: 341 Registered: August 2009 Senior Member Thats exactly what I was looking for. Not that I will change anything as of yet cause I did find a source for the original Germanium type at a reasonable price. I just got the 2N174's today which are like a NTE105 or the HEP233 that were in the regulator section and I also scored a ECG213 pair for the outputs like the ones that were in there. I put new 2N301's in place of all 5 transistors just to get it going and kind of an experiment. Turns out it works pretty good with them. I just wanted the info so I am able to check and correct bias when needed. Thanks chicagobill for the help! Steve C Steve C Report message to a moderator

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