Results 1 to 3 of 3

Thread: Ampeg B2 test points and bias

  1. #1
    Supporting Member
    Join Date
    Apr 2009
    Location
    NY, NY
    Posts
    576

    Ampeg B2 test points and bias

    Hi all, I just finished rebuilding the output of a B2 and I have a couple of questions regarding the TP voltages. With a 1v signal in on pin 2, no load, TP7 and 8 measures 5.8 and 5.2vdc. And on TP9 and 10 there's 38vac on each and 2vdc apiece.
    The 38vac and 2vdc are low compared to the schematic, is there a problem here?

    Also, is it better not to bias until the mosfets are mounted to the heatsink? I'm find that the 27mvdc or so is going up as they get hot.

    thanks!

  2. #2
    Senior Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    18,053
    Um, you are operating the amp with the outputs not heatsunk? NONONONO!!! They will fry themselves. Like running a car engine without the radiator connected.
    Education is what you're left with after you have forgotten what you have learned.

  3. #3
    Supporting Member
    Join Date
    Apr 2009
    Location
    NY, NY
    Posts
    576
    Many Thanks Enzo!! Close call. I probably would have fried them if I didn't post here and continued on. Anyway, they survived.
    Put the board back in and marked the board with sharpie at the test points and pulled the small AC board to read the 2 mosfets that lay underneath.
    I biased them to the average 25mv.
    The amp plays fine. I'm still a bit concerned about the 38vac 2vdc on TP9 and 10.
    Is there a problem with that?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Are these test points ok?
    By flatfive in forum Maintenance, Troubleshooting & Repair
    Replies: 3
    Last Post: 10-05-2011, 05:01 PM
  2. adding bias pot and test points to pignose 40(HELP)
    By SoulofSound in forum Mods & Tweeks
    Replies: 5
    Last Post: 12-11-2009, 07:58 PM
  3. Ampeg B2
    By Euthymia in forum Maintenance, Troubleshooting & Repair
    Replies: 7
    Last Post: 02-18-2009, 06:22 AM
  4. Ampeg B2 RE
    By johnburmicz in forum Maintenance, Troubleshooting & Repair
    Replies: 0
    Last Post: 04-10-2008, 05:31 PM
  5. Ampeg G2-12 Test points & troubleshooting help
    By pin31 in forum Maintenance, Troubleshooting & Repair
    Replies: 0
    Last Post: 01-23-2008, 09:40 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •