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09-23-2009, 05:27 PM
| #1 |
| Junior Member Join Date: May 2009
Posts: 5
| AMPEG SVT 3 Pro
Amp keeps blowing V3, I have replaced it twice with a EH12ax7, need help, please |
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09-23-2009, 10:27 PM
| #2 |
| Senior Member Join Date: Jul 2006
Posts: 428
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You could have just been unlucky.. all I can suggest is check the voltages as per the attached schematic and make sure the 120v is not getting through a leaky C19. Dangerous voltages inside so be careful let someone know what you are doing . Does it sound ok when its going ? |
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| The Following User Says Thank You to oc disorder For This Useful Post: | cgates56 (09-23-2009) |
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09-24-2009, 01:10 AM
| #3 |
| Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA
Posts: 10,366
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What do you mean by "blowing?" V3 is just a preamp tube, not under any stress. Shouldn't be much the circuit could do to it. But it is a cathode follower, and in this circuit it has about 120v on the cathode. SO some brands of 12AX7 object to high cathode voltage. Try a different brand.
__________________ Education is what you're left with after you have forgotten what you have learned. |
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09-24-2009, 03:37 AM
| #4 |
| Junior Member Join Date: May 2009
Posts: 5
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Looks like the tube is shorting, the filaments do not light on my tube tester , where a known good one does, I replaced V3 again with a NOS 12AX7 and the amp is up and running again I will just have to run it a few days and see, I have also order a set of JJ's that were in the unit from the factory and will install these, they should be in in a few days.
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10-08-2009, 06:31 PM
| #5 |
| Junior Member Join Date: May 2009
Posts: 5
| Fixed
I replaced all the tubes with JJ's and solved the problem, thanks for all the help. |
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