Welcome to
Azur Electronics

February 2011

Neither HP 8414A Polar Display is working correctly. Removing all the covers for access and inspecting the pcb's and wiring did not reveal any obvious faults. Both units need a good clean up. The intention is to use one unit and keep the other as a maintenance spare.

Top view
Note the Trace Align variable resistor fitted to the chassis rail.

RHS view
Bottom view
Showing A1 Z-Axis Intensity Modulator and Interconnection.

LHS view
Showing A2 Coordinate Converter ( Horizontal & Vertical Amplifiers).

RHS view
With safety cover removed showing A3 Power Supply.
DANGER: High Voltage 5kVpp
The terminal pins on Transformer T1 are very close to the safety cover. I have fitted a double layer of insulating tape on the cover to prevent the pins shorting.

S/N 2030A has a tricky fault. Initially the unit is working then after switching off then on again the +20V rail reduces to +9V approx and the IF Ref output from the 8407A is cut off. It looks if the problem is in A3 High Voltage Power Supply where the +20V drives the HV Oscillator.

Removing A3 involves disconnecting the CRT anode. I thought the blue device was an inline connector as it had a hairline split around it. In fact it is a 270kΩ resistor and was ready to break!

Luckily I had a spare HV Power Supply to swop over.

With the A2 and A3 assemblies removed, it makes cleaning the unit much easier. It is difficult to remove A1 as the wiring underneath is all soldered on.

S/N 2030A powered-up again and now there is a moveable spot on the screen, plus the +20V supply is stable.

S/N 1144A is now definitely a maintenance spare, not to be powered-up again!

Completed Troubleshooting Tree, Adjustments and Performance Tests ok.