Agilent E3646A Power Supply Repair

[TheDefpom]

Hi All,
I thought I would post this here, the first part of the repair on a Agilent E3646A dual channel power supply.

It had a fault with no output from channel 2, and then whilst diagnosing it I also lost the voltage feedback on the same channel, part one shows how I diagnose the faults, repair the voltage feedback fault, and even trick the unit into working, part 2 (once recorded) will show the repair of the actual output stage.

I intend to do a live stream on my channel in 19 hours time, I will be trying to substitute U139 (a CS8122) with a MCP100 supervisor IC to restore channel 2 output, the CS8122 is obsolete so I am working out what can be successfully used in its place, there is another part which I am waiting to arrive which is supposed to be a drop in replacement but it is also obsolete, however they can be found on aliexpress, they are probably fake but if they work I don't care!

Electrically these are very similar to other models, such as the E3647A, E3648A, E3649A, and also the E3632A, so the information I share in the video will help with repairs on those units also.