I have an 8657B signal generator that does fine at and above 1030MHz but below that, the level is uneven and down about 10 to 15 dBm. I have traced the (or at least a) problem to a defective HET switch, part number 08657-67102, which switches the outputs to the mixer or to the doubler, depending on the frequency chosen. There is about -3.5 VDC on the connector on the HET switch that comes from J303 on the A6 board that supplies the 0.1 - 129.999999 MHz output when that frequency is selected. This knowledge cost me an 8482A power sensor. I think there is a shorted semiconductor inside the unit. There are two control inputs that are either +12V and -12V or just the reverse, depending on the frequency chosen.
I have tracked down a replacement part and it is on the way. However, does anyone have any idea of what is inside the switch? I have been told there are two GASFET switches inside and the GASFET's are obsolete. Assuming that the replacement part solves the problem, I was wondering if it would be possible to disassemble the unit and replace the defective part (assuming I can find NOS parts) or design a new circuit that will fit in the enclosure and serve as a replacement. Does any one have any specific information on the HET switch or a suggestion do deal with the next occurrence of this problem? Thanks in advance. Joe _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.