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Greetings,?

I am finally getting back to this project and have narrowed the problem to a failing transistor in the A3 Main Oscillator. Fortunately this is a relatively easy part to get to once you know its secret hidey-hole under the large hex cap on the top of the oscillator body. (See this OCRed article from the Sept/Oct 2005 QEX magazine:??and search for HP8640 There's a marvelous description of how to disassemble the A3 unit to get to the electronics, and how to spot one of the most common problems -- loss of either +20v or - 20v at the Q1 transistor socket).

Anyway, having found the main oscillator transistor A3 Q1, and demonstrating that it was failing using a Huntron curve tracer (and some freeze spray!), I am now looking for a suitable replacement. The HP part number on the parts list is 5086-7082, whereas on the schematic itself, it's listed as 5086-4282.

So can anyone direct me to an equivalent to either a 5086-7082 or 5086-4282 NPN transistor, or a spec sheet that I can use to try and match the original?

Thanks,

Scott