Author Topic: [Solved!] Agilent E3648A Output 1 not working  (Read 940 times)

0 Members and 1 Guest are viewing this topic.

Offline GlutenizTopic starter

  • Newbie
  • Posts: 7
  • Country: se
[Solved!] Agilent E3648A Output 1 not working
« on: November 20, 2024, 07:05:58 pm »
Hi,
Today when turning on my Agilent E3648A the output 1, only shows -00.38V 0.154A Unreg and can't be adjusted, the normal clicking sound when adjusting is working but no change on voltage.

Little info:
Bought used worked for around five months then blew "GBU8J / IRF540 /  IRF2807" underload.
Replaced  "GBU8J / IRF540 /  IRF2807" on both outputs and after the repair it worked for over a year, but today this problem.
Output 2 works as intended.
Self test passes.

Tried replacing "GBU8J / IRF540 /  IRF2807" on Output 1 even though they looked good, but as guessed problem still the same
any guesses, ideas or pointing in the right direction is very appreciated.
« Last Edit: November 29, 2024, 12:42:05 am by Gluteniz »
 

Offline IanJ

  • Supporter
  • ****
  • Posts: 1818
  • Country: scotland
  • Full time EE & Youtuber/Creator
    • IanJohnston.com
Re: Agilent E3648A Output 1 not working
« Reply #1 on: November 20, 2024, 07:59:54 pm »
Big photos ouch!

Have a look on my YT channel, I have repaired quite a few of these PSU's, a couple with symptoms like yours.

https://youtube.com/playlist?list=PLFTNjqbH_TxkiYsF76ttjXmxgQeXewjSQ&si=sNvLhOM2El-gUDQG

Ian.
« Last Edit: November 23, 2024, 08:41:33 am by IanJ »
Ian Johnston - Original designer of the PDVS2mini || Author of WinGPIB
Website: www.ianjohnston.com
YouTube: www.youtube.com/user/IanScottJohnston, Odysee: https://odysee.com/@IanScottJohnston, Twitter(X): https://twitter.com/IanSJohnston, Github: https://github.com/Ian-Johnston?tab=repositories
 
The following users thanked this post: Gluteniz

Offline GlutenizTopic starter

  • Newbie
  • Posts: 7
  • Country: se
Re: Agilent E3648A Output 1 not working
« Reply #2 on: November 20, 2024, 09:05:06 pm »
Big photos ouch!

Have a look on my YT channel, I have repaired quite a few of these PSU's, a couple with symptoms like yours.

Ian.
Oops :-[

Thank you, will check them out!
 

Offline derZockerMP

  • Regular Contributor
  • *
  • Posts: 88
  • Country: de
Re: Agilent E3648A Output 1 not working
« Reply #3 on: November 22, 2024, 04:42:44 pm »
Check the DAC voltages on the test points mentioned in the schematic in the service manual. Also, test the power supply voltages. Follow the path of the DAC signals to the error amps and look for voltages that are not within specifications.
 
The following users thanked this post: Gluteniz

Offline TheDefpom

  • Frequent Contributor
  • **
  • Posts: 798
  • Country: nz
  • YouTuber Nerd - I Fix Stuff
    • The Defpom's Channel
Re: Agilent E3648A Output 1 not working
« Reply #4 on: November 23, 2024, 01:10:56 am »
I have also done repairs on sister models of this supply, I have a playlist on my YouTube channel which you may want to check out in case there are clues there for you.

https://www.youtube.com/playlist?list=PL2z3V9RkHQE2Twk6VoEBURx88TDXPKVSP

One thing to watch for is that the service manuals have many mistakes in them with values, part numbers, identifiers etc., so always double check everything and compare, as the circuit diagrams are not always correct for these.
Cheers Scott

Check out my Electronics Repair, Mailbag, or Review Videos at https://www.youtube.com/TheDefpom
 
The following users thanked this post: Gluteniz

Offline GlutenizTopic starter

  • Newbie
  • Posts: 7
  • Country: se
Re: Agilent E3648A Output 1 not working
« Reply #5 on: November 23, 2024, 10:02:56 pm »
Thank you very much for the help and useful info and videos!

Today I took some measurements of the BIAS supply and noticed the biggest difference being the +15v is 14.15v and not sure if this is out of spec?
Also followed the path and found that U136 on pin 5 I can see the voltage change from -0.334v to 1.034v when adjusting from the front panel but the output pin 7 on the U136 always stays at 9.21v
so I replaced the U136 (TL074CD) but it did not solve this problem.


Attached a few pictures of my measurements.
 

Offline TheDefpom

  • Frequent Contributor
  • **
  • Posts: 798
  • Country: nz
  • YouTuber Nerd - I Fix Stuff
    • The Defpom's Channel
Re: Agilent E3648A Output 1 not working
« Reply #6 on: November 23, 2024, 10:15:58 pm »
It has been several years since I worked on these myself so my memory is pretty poor on them, but U132 and U135 control the output as well, if I remember rightly they are used for over current, over voltage etc, so if they see a fault they shunt the gate drive to shut it off, you will notice all three device outputs are connected together through diodes.

I remember looking at those in my repairs years ago trying to trace a no output fault, I think in that case it ended up being a bad supervisor IC that checks the 5V supply rail, I showed that in one of the videos.
Cheers Scott

Check out my Electronics Repair, Mailbag, or Review Videos at https://www.youtube.com/TheDefpom
 
The following users thanked this post: Gluteniz

Offline IanJ

  • Supporter
  • ****
  • Posts: 1818
  • Country: scotland
  • Full time EE & Youtuber/Creator
    • IanJohnston.com
Re: Agilent E3648A Output 1 not working
« Reply #7 on: November 24, 2024, 12:41:47 am »
Common problem with these PSU’s are the green coloured SMD resistors, they often go open circuit or high value. They are affected by humidity.

For your fault you need to break it down.
1. Check all power supply rails.
2. Check the user adjustable voltages for I and V after the DAC, also including the setpoint signals.
3. Check where these signals are split off for the display, the ADC.
4. Check where the main signals come together and are basically OR’d to drive the main pass transistor.

The manuals for these often have quite good repair guides.

Ian
« Last Edit: November 24, 2024, 12:58:10 am by IanJ »
Ian Johnston - Original designer of the PDVS2mini || Author of WinGPIB
Website: www.ianjohnston.com
YouTube: www.youtube.com/user/IanScottJohnston, Odysee: https://odysee.com/@IanScottJohnston, Twitter(X): https://twitter.com/IanSJohnston, Github: https://github.com/Ian-Johnston?tab=repositories
 
The following users thanked this post: Gluteniz

Offline GlutenizTopic starter

  • Newbie
  • Posts: 7
  • Country: se
Re: Agilent E3648A Output 1 not working
« Reply #8 on: November 29, 2024, 12:40:20 am »
Problem was found, a failed TL072AC.

Thank you very much to all of you that took the time to reply with great info and also videos!  :-+
now fully calibrated and back in the bench ready to serve :box:

 
The following users thanked this post: bingo600, derZockerMP

Offline derZockerMP

  • Regular Contributor
  • *
  • Posts: 88
  • Country: de
Re: [Solved!] Agilent E3648A Output 1 not working
« Reply #9 on: November 29, 2024, 07:05:33 am »
Good job :-+
 

Offline IanJ

  • Supporter
  • ****
  • Posts: 1818
  • Country: scotland
  • Full time EE & Youtuber/Creator
    • IanJohnston.com
Re: [Solved!] Agilent E3648A Output 1 not working
« Reply #10 on: November 29, 2024, 11:28:39 pm »
Great to hear.
Ian Johnston - Original designer of the PDVS2mini || Author of WinGPIB
Website: www.ianjohnston.com
YouTube: www.youtube.com/user/IanScottJohnston, Odysee: https://odysee.com/@IanScottJohnston, Twitter(X): https://twitter.com/IanSJohnston, Github: https://github.com/Ian-Johnston?tab=repositories
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf