[Test-Equipment] HP 403B AF voltmeter

[Ken & Marlene Grant]

I've just bought one of these units. It didn't come with the battery pack, so I made up an array of zeners, fed from the built-in battery charger, as a substitute. Is this a legitimate way to power the instrument or was it really meant to be battery powered? How critical are the supply voltages?

 Also, on power-up, the meter movement goes full scale momentarily before trying to settle down to zero ( which it doesn't manage to do, on the lower scales ). Is this normal? The manual doesn't mention such behaviour.

 I have it opened up on my bench. Could it be picking up external 'hum', accounting for the inability to zero?

 I'd really appreciate any help or advice from the group. Ken, VE3FIT