[volt-nuts] J511 current regulator diode (FET) temperature coefficient

David C. Partridge david.partridge at perdrix.co.uk
Thu Jul 5 01:04:00 UTC 2012

I *think* I may be getting somewhere in finding the drift problem in the AC buffer of my 7081.

Measuring the voltage drop across R718 which is the 100 ohm collector resistor for TR703, I see a huge change just taking the lid off the meter:

Lid on: 0.45200V after 8 hours powered on
Lid off: 0.45750 after about 20 seconds and climbing, almost 0.46V after 1 minute.
Lid on: Voltage slowly drops off, 0.456 after a few minutes and dropping. 

The voltage across this resistor was almost 0.5V at power on from cold.

Are these diodes subject to failing with poor temperature regulation?  


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