HP 3406 RF Voltmeter

[Andrew Tweddle]

I am trying to repair the probe on this HP Voltmeter.
The diodes in the diode bridge part of the circuit are blown. There is
no mention in the manual of what they are. They measure 0.3 volts in one
direction and high in the other. I assumed they were probably germaniuns.

The numbers on the originals were

HP
387
848

as you view around the barrel.

I substituted some 5082-2804 matched pair schotkys but the sensitivity
wasn't very good.
What were the originals?
Any ideas?

Andrew

 

[Jorgen Lund-Nielsen]

Andrew Tweddle schrieb:

I am trying to repair the probe on this HP Voltmeter.
The diodes in the diode bridge part of the circuit are blown. There is
no mention in the manual of what they are. They measure 0.3 volts in one
direction and high in the other. I assumed they were probably germaniuns.

The numbers on the originals were

HP
387
848

as you view around the barrel.

I substituted some 5082-2804 matched pair schotkys but the sensitivity
wasn't very good.
What were the originals?
Any ideas?

Hello Andrew,

that's weird,
i have used 5082-2805 Matched Quads to repair the 3406 and
the nearly identical sampling heads of the 8505 Vector Voltmeter
with success.
Maybe there is more blown than the diodes? Or the two pairs you are
unsing
are too different and the Bridge Balance is too far away?


Jorgen
dj0ud

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