Results 1 to 6 of 6
Like Tree1Likes
  • 1 Post By Enzo

Thread: valvastate 8008 blowing secondary fuses

  1. #1
    Junior Member
    Join Date
    May 2008
    Location
    Norway
    Posts
    15

    valvastate 8008 blowing secondary fuses

    Need help
    valvestate 8008 blowing both secondary fuses (6.3a)
    checked cables, tranny,rectifier and pilot-led.
    thinking problem is further in.
    any ideas ?

  2. #2
    Senior Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    28,470
    Well, yes. When fuses blow, the MOST likely failure is a shorted power transistor. Check the output transistors on the heatsinks for shorted condition. probably only one of the channels is blown. You will probbly find the transistors are BDV64 and BDV65. if one of the pair is shorted, replace the other one too.

    You can replace the BDV types with TIP142 and TIP147. Watch your polarity. and those TIP types come in several shapes, so get the right ones. (TO3P if I recall.)
    Attached Thumbnails Attached Thumbnails marshall-8008.pdf  
    Cygnus X1 likes this.
    Education is what you're left with after you have forgotten what you have learned.

  3. #3
    Junior Member
    Join Date
    May 2008
    Location
    Norway
    Posts
    15
    You were right.

    desoldered both bdv64 transistors, and there was a difference, when measuring between the mid and right leg. the one (of witch i presume is faulty) had a connection. the other transistor didn't.
    now i'm gonna order and change all four transistors.

    BUt... there is also a small transistor on the same rail..
    (tip 29 c)
    could this one be damaged as a result of a damaged bdv 64 ??

    thank you very much

  4. #4
    Senior Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    28,470
    Don't know, you would have to test it. In my experience, it will be OK, but every case is different.

    Check any of the rectangular cement power resistors you see. They can burn open without looking different. Values are printed on them.
    Education is what you're left with after you have forgotten what you have learned.

  5. #5
    Junior Member
    Join Date
    May 2008
    Location
    Norway
    Posts
    15
    Hello

    Thank you very much for the help.
    changed all four transistors today.
    and measured for any short circuits, before plugging in.
    the amp worked like a charm.

  6. #6
    Senior Member
    Join Date
    May 2009
    Posts
    123
    Digging up this old thread to say thanks, and point of clarification for
    others who might be searching.
    My 8008 shorted out on both TR4 and TR18.
    Checked shorted on both with 1 ohm between middle and right side pins.

    BDV65C, replaced with NPN TIP142
    BDV64C...replaced with PNP TIP147.
    Working fine and running cool.

    Thanks again!

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Classic 30 blowing fuses...
    By HojoMojo in forum Maintenance, Troubleshooting & Repair
    Replies: 11
    Last Post: 06-29-2008, 09:12 PM
  2. Blowing Fuses
    By EETStudent in forum Maintenance, Troubleshooting & Repair
    Replies: 11
    Last Post: 05-08-2008, 07:10 PM
  3. Blowing Fuses....
    By Bob M. in forum Maintenance, Troubleshooting & Repair
    Replies: 10
    Last Post: 03-28-2008, 07:18 AM
  4. Blowing fuses
    By lowell in forum Maintenance, Troubleshooting & Repair
    Replies: 7
    Last Post: 03-24-2008, 01:14 AM
  5. Blowing fuses...
    By riscado in forum 5 E 3
    Replies: 7
    Last Post: 08-21-2006, 04:06 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
  •