Agilent 6632B Repair

This is the second 6632B that I bought from eBay in condition "For parts or not working".

The inside of this unit was very clean, so the blown Tantalum-capacitor on the supply rail of the processor board immediately caught my eye. After removing the shorted capacitor, the power supply was working again without any problems.

exploded tantalum — Exploded tantalum capacitor

Anyway, I replaced the Tantalum with a 50 V 4.7 uF MLCC.

fixed processor board — Processor board with fixed capacitor

I also fixed the design flaw mentioned by "Dr. Frank" on the eevblog Forum by adding the missing ground connection to the input capacitors on the main/analog board.

The rotary encoder on this unit was also broken and replaced by an ALPS EC16.

broken encoder — The leaning tower of Pisa

fixed encoder — New encoder with replacement knob, as the original part is not available anymore

ToDo:
"There is a possible glitch on the output due to an AC Line sag between 23 VAC to 27 VAC." Service Note 9

Edit: Fixed with a simple 1N4148 Diode.

Links
Datasheet: keysight.com
Service Manual: keysight.com