Author Topic: AB528 phantom power issue

June 17, 2023, 10:56:52 AM
Read 1845 times

BramP

  • Newbie
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
Hi, so I received my AB528 kit last week, very nice and professional kit with excellent build documents, I manager to finish it up in just a couple of hours and it sounds wonderful!

However, there seems to be an issue with the phantom power; when I use a condenser mic now and again the phantom power seems to randomly cut out for a minute or so. After turning the mic pre off and on again the phantom power's back. What could be the issue here?

Gear used: Midas L6 lunchbox, Brauner Phanthera mic, only other module installed is a Zahl EQ1
« Last Edit: June 17, 2023, 10:58:31 AM by BramP »

June 17, 2023, 05:37:54 PM
Reply #1

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1117
  • Karma: +37/-0
    • View Profile
The phantom voltage goes directly from the lunchbox to the mic via SW1, R3, R1, R2. Check the solder joints on these components.
JPK

June 18, 2023, 03:27:21 PM
Reply #2

BramP

  • Newbie
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
I've resoldered the resistors there and been recording with it for a couple of hours after, problem seems solved! Awesome :)

Great preamp, won't be the last thing I'll be ordering from Sound Skulptor ;)

Greetings, Bram

October 09, 2023, 08:46:10 PM
Reply #3

BramP

  • Newbie
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
Hi unfortunately the issue is not yet resolved, the preamp intermittently shuts off at random times (maybe once every 15-20 hours that it's on or so), the signal indicator keeps working but there's no output. After a couple of minutes and turning it on and off again it then works again. 

I'll check the board and resolder any suspicious connections, or could this indicate a failing part somewhere?

Still enjoying the sound, but in this state it's too risky to use in a tracking session. 

October 11, 2023, 11:13:44 AM
Reply #4

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1117
  • Karma: +37/-0
    • View Profile
This looks like a bad solder joint.
You could leave the pre on, waiting for a failure and when it happens, check if you can measure the signal on TP2, TP3 and TP4. this would narrow the search field.
JPK

October 15, 2023, 09:01:38 PM
Reply #5

BramP

  • Newbie
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
Resoldered and cleaned up some of my sloppy work, fingers crossed :)