HawkeyeKane
1147 posts
Aug 29, 2012
6:54 AM
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I finished my 'Zoo up, as you can see in my previous thread. However....it would seem that I made a very silly mistake.
Looks like when I put the tubes back in, for whatever reason, I managed to flip-flop the V1 and V2, so the 12AX7 was in the power socket and the EL84 was in the preamp.
Luckily I caught what I had done....but not before I had turned it on for about thirty seconds. I haven't turned it on again since outta fear that I've damaged something. I caught a whiff of melted plastic in the air when I had it on, but after I turned it out and stuck my nose in the amp, I didn't smell it, so maybe my soldering iron was touching something else.
What do you think? Turn her on again? Or have I fried my OT in the process?
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Hawkeye Kane
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Greg Heumann
1760 posts
Aug 29, 2012
8:08 AM
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Hi, Hawkeye
Sorry to say generally speaking that will blow something up. You may have gotten it in time. There's a 3.3K resistor from the rectifier socket to the power tube socket. With the amp off and safe check that resistor.
It can also blow the rectifier tube or smoke the transformer, especially if the fuse in there was bigger than 1A.
I would suggest pulling all the tubes - then check that you have good AC supply from the power transformer. (BE CAREFUL with all of this!)
Then plug in the rectifier tube and confirm DC voltages at each power filter cap. (BE CAREFUL with all of this!)
Now power down, plug in the rest of the tubes in the right position of course..... Doubtful you could do any more damage this way.
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/Greg
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HawkeyeKane
1149 posts
Aug 29, 2012
8:52 AM
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I'll take a peek in the chassis today. What about a dim bulb tester? I just built one and I've read from tube radio gurus that it's a good way to make sure the DUT is electrically sound.
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Hawkeye Kane
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HawkeyeKane
1150 posts
Aug 30, 2012
9:32 AM
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Crisis averted.
I looked in the chassis to make sure all resistors and caps were intact and not burned out. Plugged the tubes in their correct spots, turned it on, and she works just fine. Thanks for the help Greg.
BTW, I've got a local guy with another blackface Deuce who saw my cabinet. Says he'd like a hardwood cab for his too. Looks like I may have found a niche. :-)
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Hawkeye Kane
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Greg Heumann
1762 posts
Aug 30, 2012
11:57 AM
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Don't just look. You should MEASURE that 3.3K resistor. It is one of the standard checks I do because they frequently are burned up - raising the resistance to as much as 6K. At that point the amp ain't going to function as well. Often they don't show any outward signs.
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/Greg
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chromaticblues
1328 posts
Aug 31, 2012
5:40 AM
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I wasn't going to say anything, but sense Greg did.
If you smelled something burning. Something IS wrong now! Check all the power T voltages. I bet one of them are low now. Or it will stop working in the near future. Find out what it is now and replace it or your going to have a bigger problem soon.
Just trying to help Hawkeye!
You did a lot of work and it's nice, but your not done yet! If you don't know how to test any of this stuff just ask!
Last Edited by on Aug 31, 2012 8:48 AM
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HawkeyeKane
1153 posts
Aug 31, 2012
8:51 AM
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I'm planning to give it a thorough examination tonight. My multimeter crapped out on me a little while ago, so I had to borrow one until I can mosey down to Harbor Freight and get a new one. But I'll let you all know what comes of my probing the chassis tonight.
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Hawkeye Kane
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MP
2429 posts
Aug 31, 2012
12:57 PM
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my Zoo broke down a few nights ago. i was heartbroken so we were both broken.
MojoKane lives next door to me. he just bought a FleaBay Zoo. i was taking him to the airport. We removed the Brains from our Zoos and we were going to get them worked on by local The Amp Guru. BUT....
fricken MojoKane Spotted the Short on my Zoo! Saved me a PACKET!
Good luck Hawk, Aloha Mark
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MP
affordable reed replacement and repairs.
"making the world a better place, one harmonica at a time"
click user name for info-
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