The Agilent E3632A is a programmable linear 120W DC power supply. I got my unit a couple of years back. Since then, I replaced the RIFA caps and the noisy fan. The other day it developed a little issue: The power switch plunger detached from the switch. And now the plunger is inside the unit. Let’s fix that and take one or two pictures along the way…

❗ Caution

All information is provided “AS IS”, without warranty of any kind, express or implied.

❗ Caution

The elevated voltages inside this amplifier can cause damage, severe injury, and death. If you are not authorized or qualified to work on such equipment, do not do it. If you follow along, you do so at your own risk.

The Agilent E3632A has a massive EI core transformer.
The Agilent E3632A has a massive EI core transformer.

The large mainboard seems to have three layers. Interesting choice…
The large mainboard seems to have three layers. Interesting choice...

The silkscreen on the bottom of the PCB is really helpful. AC goes to a bridge rectifier CR11 and also to an SCR (CR14, CR17, CR18, CR19) for the high range. The rectified current is filtered by C36, C46, C65. Two power transistors (MOSFETs) regulate the output (Q3, Q4). The current is measured at the two (paralleled) current shunt resistors R129 and R140. CR37 and CR38 are protection diodes for reverse polarity on the output (output, sense). U12 and U16 are voltage regulators for the bias supply. Nice.

Of course the plastic plunger broke. I think a bit of epoxy should fix it…
Of course the plastic broke. I think a bit of epoxy should do the trick...