Electronics > Repair
HP E3615A power supply slow ramp up
<< < (3/7) > >>
pqass:

--- Quote from: gaminn on August 27, 2024, 03:20:46 pm ---FYI I have another good E3615A power supply. This is the startup waveform of U9B output. U9B output also experiences slow drift of approx. 15 mV within the first minute (3.466V to 3.480V).

--- End quote ---

By "good" you mean the +OUTPUT to -OUTPUT is stable during the first minute after a cold start yet U9B output still experiences a 15mV drift?
I'm at a loss to explain this.

The only other thing I can think of is R62 or R82 changing in the first minute.  But the mW=3.8 and 0.9, respectively (@20V across R62 and @5V across R82).  That's "half a bees dick." --D. Jones
gaminn:
By "other good power supply" I mean the other unit I have which doesn't have slow ramp up, the output voltage is stable within a second after I turn it on. U9B output in this unit still has similar drift as in the faulty unit with slow ramp up.
pqass:

--- Quote from: gaminn on August 28, 2024, 01:35:31 pm ---By "other good power supply" I mean the other unit I have which doesn't have slow ramp up, the output voltage is stable within a second after I turn it on. U9B output in this unit still has similar drift as in the faulty unit with slow ramp up.

--- End quote ---

My guess would be that's due to the MOSFETs settling in then.

The additional 5mV drift could be from R62, R82 or C29 changes.

Try replacing R62 with a 100K+4K7 or C29.
gaminn:
I'm now waiting to receive LF347BN from Mouser, hopefully it is this opamp that is faulty. Meanwhile I disconnected all components that are not "necessary" - CR22, R19, C36, C29, CR28, CR27, C37. I replaced R82 and R62. It didn't change anything. I can't even find some components (R125, C62, C67) on the PCB of my E3615A power supply , so I think the schematic is not 100% accurate.
gaminn:
Unfortunately, replacing U9 (LF347BN) didn't help. Another idea how to fix this issue?
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod