Ampeg B-15N Replacement Power Transformer

Discussion in 'Amps and Cabs [BG]' started by Turbocharbo, Dec 3, 2020.

  1. Hey all

    My '66 Ampeg B-15N started blowing its main fuse last night. I'm bringing it to my tech to get it fixed up tomorrow but I can't help but imagine the worst case scenario which would be that it needs a new PT. If that is the case, what is the best replacement out there right now? As far as I know the PT is not in the audio path but will a replacement make it sound different? Is anyone out there re-winding these?

  2. 40Hz

    40Hz Supporting Member

    May 24, 2006
    Mercury Magnetics offers one for $250. They’ll re-pot it in the original can if you send it to them.

    But wait until your tech tells you it needs to be replaced. He/she probably has their own sources for a replacement or rewind if it’s actually needed. Odds are it isn’t the power transformer that’s the issue.

    Luck :thumbsup:
    Last edited: Dec 3, 2020
  3. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Rather than guess about a worst case scenario, proper diagnostics troubleshooting will determine what exactly has failed and WHY. Sometimes a component fails and causes damage to other components, without thorough diagnostics, this wouldn't be discovered.

    I was just talking with a tech this morning about the declining level of technical aptitude whe have been seeing in service centers in general lately as the top guys have been retiring and/or aging out. This is a big deal as the best techs also provided the best service and didn't stick the customer with parts and labor that weren't necessary. The hobby techs and tinkerer techs and especially those who were educated on the internet are the very worst techs to deal with. It's like talking to a wall, they already know it all and continue to insist that through repair failure after failure. Beware, and seek out the most qualified tech you can possibly find.
  4. beans-on-toast


    Aug 7, 2008
    The tech will test the so called death cap on the primary side of the power transformer for any shorting. Next they would decouple the secondary and test each tap, 750 VAC, 6.3 VAC and 5 VAC as well as the 117VAC primary. If that checks out, they will look at the rectifier and power supply and bias circuits. Also the hum balance pot on the heater.

    Should you need a new transformer, the best choice in my opinion is the Heyboer from
    Last edited: Dec 3, 2020
  5. Thanks for the replies. My guy is an older guy with over 50 years experience, not one of those internet techs. I'm just prepping myself for the worst case scenario and also interested in knowing what the options are out there for PTs. I'm in Canada so sending my OG enclosure to Mercury Magnetics is probably not the most feasible option.

    Will a PT swap impact the sound of the amp at all?
  6. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Agreed on getting the proper diagnosis for the amp before jumping to conclusions.

    That said, you see a lot of B15Ns in the field with replaced PTs. I agree with the @beans-on-toast above, the Heyboer/Fliptops route is the way to go. You ship them your old can/PT and they pot a new heyboer into the can and send it back. Looks like the current rate is $215, I think it may have been a little cheaper when I had mine done a few years ago. They're in Buffalo, NY and I'm sure Bruce can help you manage shipping to/from Canada.

    It should not impact the sound of the amp so long as everything it working to the correct spec prior to and following the swap.
  7. I didn't know Fliptops could re-pot a new x-former in the OG enclosure. I thought only Mercury did that... good news!
  8. beans-on-toast


    Aug 7, 2008
    Fliptops also sells the complete transformer mounted in a new can so it isn’t necessary to return your old one. With the higher shipping charges from Canada to NY the just within the US, it would be more cost effective to just buy the new can.

    The Heyboer transformer is a better unit that the original.

    With the experience that your tech has, if the PT has an issue, he might have an alternate solution such as repairing it or installing a Hammond PT in the original can .

    The original PT-108 specs are: 750VAC CT @ 150mA, 5 VAC @ 3A, 6.3 VAC CT @ 5A
    DavidBassista, Wasnex and Turbocharbo like this.
  9. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Relax, there are lots of more likely (and less costly) causes for blowing a fuse than a bad power transformer.
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Not if you listen to the internet ;)
  11. Do not forget to replace the caps and tubes as well. :woot:

    (JOKE!) They are most likely fine. :smug:
    dbase likes this.
  12. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    The PT does not influence the sound but the OT does. Still, it's worth it to get a good one if it needs replaced. I strongly suggest Heyboer as well. Decent prices, good people. PT's in B-15's do sometimes need replaced because older ones were potted with wax and they can sometimes melt down. But just remember the saying my dad invented...if it ain't broke, don't fix it.
    DJ Bebop, agedhorse and Turbocharbo like this.
  13. I feel pretty relaxed.
    rickdog and S-Bigbottom like this.
  14. Thanks! In any case, it's good to know what's out there and what peoples opinion are on them.
    Last edited: Dec 3, 2020
    beans-on-toast likes this.
  15. Whoa! Slow your roll, my friend.:hyper:

    I have had two old Ampeg tube amps that started to blow fuses and neither had anything at all to do with a transformer. Get it checked. But if all you are doing is asking what your worst-case scenario is, fine. But given all the things it could be, the odds are it is not.
    Last edited: Dec 3, 2020
    Turbocharbo likes this.
  16. I never jumped to the conclusion that the PT was the issue, just got me curious about what's out there.
    Basslice likes this.
  17. dbase

    dbase Gold Supporting Member

    Jan 3, 2008
    South Jersey, USA..
    If you wrap some aluminum bubble gum wrapper around the fuse it will enable you to find the problem... just sayin ;)
    Jeff Scott and S-Bigbottom like this.
  18. Koshchei


    Mar 17, 2019
    Peterborough, ON
    I hope you're joking. If you are, it's 2020, so forgive me for being slow on the uptake -- this has been a really rough year.
    agedhorse likes this.
  19. dbase

    dbase Gold Supporting Member

    Jan 3, 2008
    South Jersey, USA..
    I am kidding, but I've done that before when I didn't have a fuse available. Don't tell Agedhorse ;)
  20. jmlee

    jmlee Catgut? Not funny. Supporting Member

    Jun 16, 2005
    Halifax, Nova Scotia
    Amongst Murphy's Laws of Electronics:
    "In the event of an overload, the most expensive component in the circuit will sacrifice itself to protect the fuse."