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Old 19th Jan 2021, 12:24 pm   #1
LA9CHA Thorvald
Join Date: Dec 2019
Location: Egersund, Norway
Posts: 85
Default More HP8640B info!

A bit more, checked the square wave signal going into the filter unit. This was ok, but there is no output signal. From the circuit diagram "Divider filter assy 10840-60105 (A10A2) I see that the signal has to pass the relay K1-2-3-4 contacts. The +/- 5,2V is ok, and the relays are operated via "op.amp" U6A and B. Either one is on and the other is off. These are again controlled via transistor Q1 that creates a inversion of the signal from U1. So, if the U1 is defective, neither relays will be operated (correct?). the input signal to U1 changes level from 0,00V to 0,5V when changing bands. Any comments arte welcome!
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