Colas LeGrippa
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« on: March 22, 2012, 06:47:11 pm » |
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Why would an output transformer have a primary lead tied to gnd ? The amp is an Ampeg Jet J12, no such wire appears on the schem, strange or am I missing something ?
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Don't miss the Woodstock experience : ''FORTY YEARS AFTER'' at Club Soda, in Montreal, august the 17th and 18th and october the 27th. Fifteen musicians onstage. AWESOME !
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Dave
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« Reply #1 on: March 22, 2012, 08:07:08 pm » |
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Maybe its just a ground wire for the bell like you find in some power transformers?
Dave
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HotBluePlates
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« Reply #2 on: March 22, 2012, 08:30:35 pm » |
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Can you post a picture of it? As you say, it's not on the schematic.
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From Principles of Electron Tubes: "... the phase of the output voltage is retarded."
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Colas LeGrippa
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« Reply #3 on: March 22, 2012, 09:11:17 pm » |
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my camera is out for the moment, but let me explain : it is a push pull tranny : as usual : red HV, blue plate no1 , brown plate no 2.......and unusual: grey to ground. It is not the gnd from the secondary that has it's own.
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Don't miss the Woodstock experience : ''FORTY YEARS AFTER'' at Club Soda, in Montreal, august the 17th and 18th and october the 27th. Fifteen musicians onstage. AWESOME !
P.S.: call me Alvin.
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jojokeo
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« Reply #4 on: March 22, 2012, 10:10:38 pm » |
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With power off, disconnect it and do a continuity check. Then I'd power up the amp with this being taped off. I've only seen OT's (Mercury) where they would ground the voice coil side. Doing that on the primary is very odd indeed.
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Ritchie200
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« Reply #5 on: March 22, 2012, 11:36:06 pm » |
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Is that a UL amp?
Jim
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 My religion? I'm a Cathode Follower! Can we have everything louder than everything else? My old man is a television repairman, he's got this ultimate set of tools!-Spicoli |
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HotBluePlates
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« Reply #6 on: March 23, 2012, 08:09:43 pm » |
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It might be an electrostatic shield. Does the OT have a copper band around the core?
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From Principles of Electron Tubes: "... the phase of the output voltage is retarded."
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Colas LeGrippa
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« Reply #7 on: March 23, 2012, 10:44:36 pm » |
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no, it is an output transformer ''naked'' as my girl friend is, just beside me ( she's passing the broom, but don't think I am a macho, I just spent three days on doi'n the ceramic floor in the basement, while she were on her facebook, now it's her turn to work a bit hey hey ).
Colas
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Don't miss the Woodstock experience : ''FORTY YEARS AFTER'' at Club Soda, in Montreal, august the 17th and 18th and october the 27th. Fifteen musicians onstage. AWESOME !
P.S.: call me Alvin.
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tubeswell
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He who dies with the most tubes... wins
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« Reply #8 on: March 23, 2012, 11:54:15 pm » |
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As HPB says, it might be an electrostatic (faraday) shield (between the primary and secondary windings)
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Just tryin' to keep my Rs clean. OK?
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Colas LeGrippa
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« Reply #9 on: March 24, 2012, 09:03:32 am » |
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It is very unsusual, never seen that b4
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Don't miss the Woodstock experience : ''FORTY YEARS AFTER'' at Club Soda, in Montreal, august the 17th and 18th and october the 27th. Fifteen musicians onstage. AWESOME !
P.S.: call me Alvin.
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jim
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may the pure orange light shine upon you
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« Reply #10 on: March 24, 2012, 09:20:38 am » |
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Some are manufactured with that lead soldered to the cover that is screwed to the chassis. The lead would end up on chassis ground anyway because of your output jack.
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The music industry is a cruel and shallow money trench--a long plastic hallway where thieves and pimps run free and good men left to die like dogs. There is also a negative side.
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sluckey
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« Reply #11 on: March 24, 2012, 10:54:14 am » |
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I bet there's no continuity between that grey wire and the primary. Just because the grey wire exits the OT through the same hole as the primary wires doesn't mean it's actually connected to the primary winding. Have you done a continuity check yet?
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Colas LeGrippa
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« Reply #12 on: March 24, 2012, 11:34:26 am » |
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not yet , i'm working on it, I have checked all grounds, solders, tubes , rectifier..........could it be the multiple cap can ? though all voltages read fine. All coupling caps leak .200VDC , is that too much ? the power tranny has been replaced but the guy who did it taped off the heaters ct lead......the ac cord has been replaced as well for a three lead one but the grnd was not connected to the chassis.....to make a long story short, I am correcting lots of errors, but the HUM' s laughing at me :  ''FIND ME IF YOU CAN, I'M WELL HIDDEN''  I will swap the OT temporarily for a new one and see what happen............  Colas The Gripper |
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Don't miss the Woodstock experience : ''FORTY YEARS AFTER'' at Club Soda, in Montreal, august the 17th and 18th and october the 27th. Fifteen musicians onstage. AWESOME !
P.S.: call me Alvin.
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