[Test-Equipment] HP-8405A Operation (repair?)

[k3hx at juno.com]

Greetings,

I a new member and this is my first post.


I've looked through the archives but have been unable to find any posts

regarding this unit.


Picked up the H-P 8405A Vector Voltmeter at a hamfest as part of a

"lot" of H-P test gear.


Although I've used H-P gear on and off since the mid-1960's, have no

experience with this model.  


This unit came with the modified BNC "TEE" connectors.


I tried to measure the electrical length of a piece of coax by using

an MFJ-259 as a signal source. This on 144 mHz, a piece of coax I knew

to be .25 electrical wavelength (trimmed it on a 3677 network analyzer

during a slow time on the job, some years ago.)


The APC locked up just fine but the "Degrees" meter was all over the 

place, unstable and no setting of either "Range" or "Offset" tamed it.

The "Phase Finder" was of no use.


When the unit is just sitting there, with nothing connected to the

test leads, The "Degrees" meter jitters, the APC indicates Unlock

and the dB meter rests at "0."


I'd be grateful for any words of wisdom, counsel or advice regarding 

how to use this device.  If it is not working properly (which I suspect 

is the case) I'd be grateful for any repair hints and tips.  I have not

the funds to have the H-P folks look at it (it is of a vintage they may 

no longer support) and don't require hair-splitting accuracy. 


My intended use for this instrument is to make traps and coaxial 

phasing lines.


73,

Tim Colbert  K3HX




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