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You might want to compare the metering circuit to that in the VA62 - which also has a similar bias supply. I fixed an "unfixable" VA62 simply by swapping the A-D converter chip around in the socket (it was put in backwards by the previous tech that deemed it "unfixable")
Sencore wasn't likely to design a different metering circuit for each or their products, so most likely, the VA62 and TVA92 are alike. Phil Nelson has a VA62 and may be able to provide some help.
IIRC, the VA62 meter circuit has some input protection diodes - I've seen them go bad as well. The SC61 meter also has the diodes that go bad - perhaps they duplicated this as well in your TVA92?
Wish I could be of more help - I've only played with a TVA92 at a Sencore Sales Presentation/Tech Training Seminar. Bitching Unit - sub the complete horizontal/sweep section of a TV (sans IHVT)!! That and their LCR meters impressed me the most.
Cheers,
__________________
Brian
USN RET (Avionics / Cal)
CET- Consumer Repair and Avionics ('88)
"Capacitor Cosmetologist since '79"
When fuses go to work, they quit!
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