Repairing Agilent E3632A Power Supply - UNREG Mode - Page 1
Forum section: electronics / repair

author: amexlive
author_rank: Contributor
timestamp: February 27, 2018, 05:43:41 pm
content: Hello, everyone,and I have a similar problem with Agilent E3632A.The problem is the following - The power supply has two levers up to 15V/7A or 30V/4Aand I noticed the power supply work not properly.At 15V/7A I have connected LED Stripe and up to 7 volts there is no change, at 8V it going to the UNREG mode and more than 9V can not give.At 30V/4A I connected an electric motor (the motor work at 24V) and as you can see in the video I have been upload here since I can turn the digital potentiometer there is no change and suddenly the 16V and more of 25V can not lift.https://youtu.be/jGSGJWt8Si4https://youtu.be/m1bI8MULyNYNow I see when I connect a multimeter at the output of the power supply that up to 7 volts there is no voltage, at 8 volts and 9 volts there is, at 10 volts the meter shows 9 Volts but it can be seen how the LED pulsates.https://youtu.be/RcACKvTSEXIAny ideas?Sorry in advance for my not good English and thanks for understandning.

author: Armadillo
author_rank: Super Contributor
timestamp: February 27, 2018, 10:59:06 pm
content: The symptom looks like you are in a constant current mode.Edit: Press "Display Limit button" and Check what voltage limit you have set.

author: floobydust
author_rank: Super Contributor
timestamp: February 27, 2018, 11:28:51 pm
content: I would look at the power section to see if it is damaged, leaving a weak power supply.Check if the pass-transistors are damaged. This is MOSFET Q4, Q3IRFP044on the heatsink. With a steady DC load, voltage drop across R11, R17 should be equal if they are correctly sharing current.The DC bus voltage (at R34, big C65/C46/C36) I would also check if it is not collapsing under load. The PSU uses SCR's to autorange and select hi/lo transformer winding, I think.The E3634A had a bridge-rectifier fail:https://www.eevblog.com/forum/repair/agilent-e3634a-power-supply-teardown-repair/

author: amexlive
author_rank: Contributor
timestamp: February 28, 2018, 08:30:41 am
content: I check the Display Limit buttonWhen I press it on the display showing:00.000V 7.000Aand I can edit it with Ajustment to the15.000V and 0.000Abut when I wait and the blinking limit symbol disappear on the display stay:-0,356V 0.057AwithUNREGsymbol

author: Armadillo
author_rank: Super Contributor
timestamp: February 28, 2018, 08:37:43 am
content: Can you adjust display limits to15.000V and 7.000A?I trust you know how to do it.

author: amexlive
author_rank: Contributor
timestamp: February 28, 2018, 08:46:53 am
content: HifloobydustI check the MOSFETQ3,Q4 R11andR17and the voltage are the same and look like ok - what I mean: the power supply accept only8Vand9Vby mode15V 7AThe power supply when I receive it (second hand) was working ok but it was so dirty. I open it to clean it and when I assebly it the problem come. I change only the filter capacitorsC91, C92, C93with new one original of RIFA.This faulty is interesting and mistake for me.

author: amexlive
author_rank: Contributor
timestamp: February 28, 2018, 08:50:09 am
content: HiArmadilloYes I can adjust display limits to15.000V and 7.000Abut the output voltage is only9Vand when I ajust it the7Vthe output voltage down slow to 0V (capacitivy)

author: Armadillo
author_rank: Super Contributor
timestamp: February 28, 2018, 09:03:18 am
content: Can you hook up a resistance of above 1K and try again.What load was you using by the way.

author: amexlive
author_rank: Contributor
timestamp: February 28, 2018, 09:27:58 am
content: HiArmadilloI try with 910 Ohm resistor and the result is the same. As load I use LED Stripe and DC Motor

author: amexlive
author_rank: Contributor
timestamp: February 28, 2018, 10:55:48 am
content: [THE PROBLEM IS FIXED]THANK YOU GUYS FOR THE HELP!I make some measurement and see thatP9andP10between thetransformerandbridge-rectifierhave not connectivity. I check it and the problem was that the cable terminal was broken. I change the cable terminal with new one and now all is perfect!Thank you again for the help!