Re: Bias current problems

Robert Hudson
 

Hi John

I use an ammeter in the supply line in series to read the current.   The receiver draws 44mA and if the Bias current  was 60mA then the total current draw would be 100mA.   It actually might be a bit less because I think some of the circuit is switched off when the PTT is pressed.  

I recently bought an FT-847 from a deceased estate which was dismantled and in a cardboard box with most of the covers missing.   I have been able to re-connect it and stall worked with VHF, UHF and HF/50mhz.  The only problem was the HF/50Mhz PA board (Power Amplifier board).  The problem was there was no bias current .   After looking around and getting the service manual and staying the circuit I found the bias pot was open circuit.  The interesting thing was that it had a 2 pin header with a link connected for normal use and you could take the link off and connect an ammeter read the bias current only with out the complication of reading the whole radio current draw.      

The way the instruction is written does not make sense to me.  So hoping to get some further explanation.   I have some other information as well to progress with the testing by shorting pins 2 and 3 which makes it operate in the AM mode of one of the NE602 chips but have to read further.   Still need to understand the Bias current setup.

Hope that explains some it for you John.


Bob Hudson







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