Dang, I think the OT blew in my '73 SVT...

Discussion in 'Amps [BG]' started by Rickenbackerman, Mar 5, 2014.


  1. Rickenbackerman

    Rickenbackerman

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    This thing has been as reliable as all getout for the last 15 years. It's still running the original GE6550A's, too. I fully recapped it long ago and changed all of the plate resistors. I usually stick it on the bench and check the bias and balance once a year or so.

    But gigging and jamming has slowed somewhat over the last few years, so it really hasn't been used much lately. A buddy called and is going on tour and asked if he could borrow it. I've got a road case for it, another working '74 SVT (also with original tubes), and they're both just sitting so I figured why not? I checked the bias and balance, they were both pretty close. He took it to practice. Worked great and sounded glorious the first night. Second night he calls and says it's smoking and no sound. I asked him where the smoke was coming from and he said under the volume knob, which is exactly where the tranny is.

    I did notice while setting the bias/balance that there was a slight hum from the OT but didn't think much of it till he called. I'll get it back soon (maybe tonight even) and pull it apart for a diagnosis. Have a feeling Heyboer is going to be getting a call...
     
  2. azwhofan

    azwhofan Supporting Member

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  3. nashvillebill

    nashvillebill

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    OT's usually don't just suddenly decide to burn up! If it's failed, something else likely took it out.
     
  4. BurningSkies

    BurningSkies Supporting Member

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    ...Like it not being plugged into a cab...
     
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  6. Rickenbackerman

    Rickenbackerman

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    Nah, this particular buddy has been running SVT's even longer than I have. I'm almost 100% sure he had it set up right.
     
  7. beans-on-toast

    beans-on-toast Supporting Member

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    It could be that a tube failed and took a plate resistor with it. That is often where you see a fire in these amps. The 5W resistor is intended to act like a fuse to protect the transformer.

    If you need a transformer, try www.fliptops.net, they sell vintage repro transformers from Heyboer. Or at least that is where they used to source them from.
     
  8. Rickenbackerman

    Rickenbackerman

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    That was my first thought, but the amp should still have made *some* sound even with 4 out of 6 blown plate resistors. He said it went dead silent.

    If it does turn out to be the OT, I'll contact Heyboer directly to rewind it. It's much cheaper than buying a whole new one.
     
  9. beans-on-toast

    beans-on-toast Supporting Member

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    I hope that isn't the problem. Don't know what Heyboer would charge you for a rewind. A new one is $269 + shipping. Either way, it's expensive.
     
  10. Rickenbackerman

    Rickenbackerman

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    I had a PT rewound by them 10-ish years ago. IIRC it was only about a hundred bucks.
     
  11. Mr. Foxen

    Mr. Foxen

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    Sure there was a hum from the OT, its the Pt that hums, shouldn't be AC outside of signal in the OT (because it would come out the speakers).
     
  12. Rickenbackerman

    Rickenbackerman

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    I didn't even try it through a cab before I loaned it to him. I set the bias and balance into my 1200W dummy load and handed it over. He's bringing it back tonight so I'll ask him if it was humming or not (and how loud).
     
  13. JimmyM

    JimmyM Supporting Member

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    Even if you replace it, contact Heyboer directly. They sell them much cheaper than resellers. Hope it's not that, though...I've had a couple techs tell me they've never even seen a stock tranny from those old SVT's blow. Not saying it's never happened, but those guys are pretty experienced.
     
  14. beans-on-toast

    beans-on-toast Supporting Member

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    That's a good price. Old iron plus new windings is better than a new one.

    Let us know what you find once you've had an opportunity to look at it.
     
  15. Mr. Foxen

    Mr. Foxen

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    Seen cooked power tranny in a 69 one. OTs tend to take special effort to go.
     
  16. Rickenbackerman

    Rickenbackerman

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    I got it back and sent him off with my '74. It flat out STINKS. Like burnt insulation. Don't have time to pull it apart tonight, but I'll keep you guys updated...
     
  17. dukeisdog

    dukeisdog Supporting Member

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    Sound like a real good friend there Rickenbackerman! Hopefully you can get the other SVT up and running for not too much $$$. Maybe he'd be willing to help with the costs considering you borrowed him two legendary amps! :bassist:
     
  18. Downunderwonder

    Downunderwonder

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    You might want to troubleshoot the guy's cab and cable before potentially toasting the '74.
     
  19. Rickenbackerman

    Rickenbackerman

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    I thought of the cab / cable, but the 810 he's running is one i sold him so i'm 99% sure it's good. And I had him inspect the cable real closely, he says it's good.

    Just in case anybody's into the stoner / doom stuff, this is for Dave Sherman of earthride / spirit caravan. Spirit caravan reformed and is going on tour again. And I was the bass player for earthride..
     
  20. beans-on-toast

    beans-on-toast Supporting Member

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    Being so intense, that stoner/doom stuff can drive amps pretty hard. Has a way of revealing issues.
     
  21. Rickenbackerman

    Rickenbackerman

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    Man, I hear that! However, they were just practicing. He said he only had the volume at 9 o'clock. I usually run that junk at 11...
     

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