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Post by tremolux on Aug 24, 2005 20:30:08 GMT -7
sad sad stuff,... so i was in a rush before our band practice and was retubing my amps (a super reverb RI and the 66 which i was running in stereo) i had a new JJ rectifier which i wanted to put in the 66 but the stock rect. tube was stuck in the socket pretty hard.. basically it came out after i gave it a hard tug instead of taking my time... so i put the new JJ 5ar4 in and flip the switch and was met with no light no sound no nothing. So i look at the pins of the old rectifier tube and see that one of the pins has something atached to it something that probably came from the tube socket.... anyway a friend took it in to a guitar shop without explaining any of this and the "amp guy" calls 2 weeks later and says that i have a short in my power transformer and should get in touch with Dr z about that lifetime warantee (mine is used though, so i dont have one) or shell out $400.
so i ask him if he looked for a problem in the rectifier tube socket and he said "my man wouldve seen something like that". so what do you guys think should i take it to another amp tech or do i really have a bad power transformer?
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Post by DRZ on Aug 25, 2005 3:14:36 GMT -7
Trem I have been working on tube amps since the late 50's ( yes 1950 that is ) , and the one thing that comes to mind is a old saying in the electronics business , " if ain't broke , don't fix it ".
I can't believe a tube swap would short out a 300 ma power transformer . If you look at the pins on a 5AR4 you'll see only 5 are there, the socket has 8 pins so the one pin the got extracted wasn't connected to anything, only four pins are connected internally.
Not sure I trust your tech's diagnosis of the problem , also to swap a $150.00 transformer , he's charging you $250.00 labor, that's eight wires and 4 bolts , nice work if you can get it.
First try replaceing the original Rectifier ( I have had problems with JJ 5AR4's BTW ) and replace the fuse 3 amp Slo-Blo, and see what happens. Make sure the amp lights up and not just the indicator lamp which may have failed, you never know.
If this doesn't help send it to me I'll fix it .
DR.Z
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Post by ducmike on Aug 25, 2005 5:30:26 GMT -7
I have had 2 JJ 5AR4's in a row fail as soon as the got power in my amp ( not in my 66 though). I would go with the Dr.'s advice. If it aint broke, don't fix it is what Steve Carr said also. BTW, the only thing harmed was the fuse.
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Post by taswegian on Aug 25, 2005 5:57:21 GMT -7
How's that for customer service! Z might have saved your amp and your bucks in one reply!
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Post by tremolux on Aug 25, 2005 6:11:44 GMT -7
thank you so much Drz and ducmike i will try this as soon as possible and keep you posted
thank you
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Post by ducmike on Aug 25, 2005 8:08:12 GMT -7
I would probably avoid that shop from now on too.
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Post by Laroosco!! on Aug 25, 2005 8:13:54 GMT -7
If there is ever an isssue with any of my Z's I contact Dr Mike.
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Post by terryg on Aug 25, 2005 9:06:49 GMT -7
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Post by tremolux on Aug 27, 2005 12:43:01 GMT -7
ok so i followed the doctor's orders and used the old rectifier tube, new slo blow fuse and plugged it all in and hit power... i got an indicator light and all my tubes were very normal looking,.. took it off standby and it went *fzzzt* and died.. the fuse blew imediatley i am examining the chassis now to try to understand why.. might have been just a lame fuse i dont know....
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Post by tremolux on Aug 27, 2005 13:01:05 GMT -7
yeah all the wiring looks fine nothing touching anything odd and no crispy fried bits.... i am perplexed
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Post by Bill on Aug 27, 2005 14:53:14 GMT -7
I had the same problem with a Ghia once...kept blowing fuses. Then I just happened to be looking at the rectifier tube when the next fuse went. Just before the amp died, a blue arc streaked across the tube. A new tube fixed the problem.
I'd try one more 5AR4...if it too blows a fuse, then 3 strikes you're out...send it to the Dr for a tweak.
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Post by tremolux on Aug 27, 2005 15:19:03 GMT -7
k thank you il give it another try
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Post by tremolux on Aug 27, 2005 15:36:22 GMT -7
the only other rectifier tube i have is the JJ though ...however i tried it anyway and watched the tube and when i switched off of standby i saw the blue arc you are talking about... but my father advised me that this could be related to the power transformer putting out incorrect voltages
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Post by DRZ on Aug 27, 2005 15:54:20 GMT -7
The drama continues.......
Trem you have a bad tube, I suspected the rectifier , because of data from your first post.
Pull all tubes except the rectifier , not sure which one is good that you have but I believe the original Sovtek is OK.
Replace fuse , connect a load ( i.e. Speaker ) and power up. If it doesn't blow a fuse , power down and install the first tube ( EF-86 ), power up again, repeat this process with adding one tube at a time till fuse blows then repllace the last tube you installed.
Hows that for backyard troubleshooting.........
DR.Z
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Post by tremolux on Aug 27, 2005 16:08:22 GMT -7
i will order some sovtek 5AR4's and do that, but what i dont understand is why the same thing happens (powers up fine but whe i switch to standby blows) with the origional rectifier tube that was working in the amp previously ...i guess it has set out in a basement a long time. thank you so much for your patience and time Drz
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Post by DRZ on Aug 27, 2005 16:42:05 GMT -7
Power switch lights the filaments .
Stand-By sw. applies the HIGH VOLTAGE, from the rectifier to the plates of each tube.
A bad tube with an internal short will draw excessive currant once Stand-by is engaged and blow fuse ( which BTW is there for protection of this exact thing ) .
I hate to guess again , BUT I would think next is a bad KT-66, if rectifier is good.
DR.Z
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Post by tremolux on Aug 27, 2005 18:35:01 GMT -7
cool, il let you know how it goes
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Post by tremolux on Aug 28, 2005 12:07:34 GMT -7
ok, it blew the fuse imediatley again with another well known to be functional rectifier tube after removing all the other tubes... sorry to keep the suspense running. At least pittsburgh isn't to far from cleveland
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Post by tremolux on Aug 29, 2005 16:57:10 GMT -7
so i guess im going to look for a box..... right? are there any last ditch efforts i could try to ressurect my amp? I really dont understand what went wrong and have a great deal of my net worth as a college student invested in this amp and would love for it to fly again.
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Post by tremolux on Sept 6, 2005 19:23:39 GMT -7
ok i guess i will send the good doctor an email
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Post by rpavich on Sept 11, 2005 4:00:41 GMT -7
How does the Dr find time to troubleshoot amps on a forum? That's why he's got such a following among those that are "in the know"...
bob
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