Author Topic: HP 3314A Power Voltage Selector Repair - Schaffner  (Read 187 times)

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Offline VK5RC

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HP 3314A Power Voltage Selector Repair - Schaffner
« on: June 09, 2019, 08:33:50 am »
A HP 3314A has been one of my bench Freq Gen - with a bit of a bug that it would only work on 100 and 120V - not our 240V line voltage. I guessed it was a transformer issue - ie too hard so never looked into it till recently. The Schematic from HP.
is for the earlier versions that have 2 separate switches.

Mine is of the later series with "soft-touch" buttons and what I nick name the "tumbling dice" all in one IEC connector, fuse holder and voltage selection switch. There is not a lot of room in the back of a 3314A so tracing out the circuit was a PITA

The voltage selector Cam activates several (2-3) of the 5 switches contained within this unit
Photo 1 - the outside view of the unit
Photo 2 the switches - with the cam removed and my labelling of the switches A to E
Photo 3 the Cam removed
Photo 4 Rob-CAD _ the switch connections and switches that the Cam activates in which positions, approximate resistance when the Active to Neutral resistance is measured
Photo 5 the Schematic  NB Switch labelled F is really switch D

The issues in my unit were
- The Black Cable wasn't connected to the assembly
- Several of the Switches weren't connecting when pressed down by the cam - a bit of judicious bending was required

Be careful not to push the cam in too hard - this flattens the switch levers - they will then either stay "ON" - pressed forward  or not reach the contact when the Cam pushes - ie stay "OFF"

If I have made any mistakes - please let me know
Hope this is of some help to others

PS This unit has one of HP better Easter Eggs

Edit error in labelling switch D in schematic - labelled as F
« Last Edit: June 09, 2019, 09:27:26 am by VK5RC »
Whoah! Watch where that landed we might need it later.

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