Hello Everyone,
Recently I have acquired two Polarad 632B-1 spectrum analyzers, none of them is working.
Unfortunately I do not have the maintenance manual or schematics. I have been trying to locate one, but so far no luck.
Any help in that?
The SAs have triple conversion architecture, going up to 2GHz, and have a 1k by 8-bit digital memory for the screen, from around 1980 or so.
Unit 1 was blowing the main fuse.
I tracked it down to a shorted tantalum capacitor on the main board, that was the filter capacitor for a 12V stabilized PS. The shorted cap took out the two-way raw voltage rectifying diodes, one of them was cracked, the other shorted, and that caused the main fuse to blow.
Having repaired these now the SA powers up, but nothing on the screen.
It looks like that the first LO is working, when the frequency span is narrow and the frequency sweep is done at the 3-rd LO, the first LO can be phase locked. The phase lock feature seems to be working, when adjusting for it the "locked" LED lights up.
Despite not having anything on the screen the CRT seems to be working, when turning the unit off, a green halo/dot can be seen traveling across the screen, so it looks like the CRT heater is working and there is HV too, except the deflection is off the screen.
The second unit initially had some display on the screen, except what was displayed had nothing to do with the input signal.
My guess is that the first LO is not working.
I do get the input signal through to the input port of the first mixer, and static measurements of the mixer with a DMM indicate as if the mixer is fine. It is a high-level diode ring based DBM, made by Polarad.
Also, the first LO can not be phase-locked, like on the other machine.
Unfortunately my "best" equipment to measure the first LO signal (2.1GHz to 4GHz) is not good enough, it is a service type SA working up to 1GHz.
As of now the display on that unit is not working either (it just stopped), there is nothing on the screen, not even a hint of the beam as on the other unit.
Here my guess would be a faulty HV-unit.
Now would be a good time to have the schematics!
Without it I can see a painfully slow repair process, comparing the modules of the two instruments to each other.
Any help would be appreciated!
Thanks, Peter