Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dd3keegs on November 05, 2010, 11:16:50 pm

Title: Ground Issues on Tweed Deluxe Replica
Post by: dd3keegs on November 05, 2010, 11:16:50 pm: Hey I just finished a Fender 5E3 Deluxe amp head. This is my 3rd amp. I've already built 2 HiOctane amp heads based on schematics from AX84.com. The Deluxe amp hums like a MOFO until I place a cable into the Normal channel inputs. This channel plays just fine. The Bright Channel has a significant hum but I do get sound out of it. Also, when I tap my finger on the chassis...the tapping is amplified through the speaker cab. I have kind of gone off the beaten path by loading the Fender Deluxe head into a 40s Delco Shortwave radio cab. Any suggestions would be appreciated.
dumb noob question. I am using a Mercucry Magnetics PT and OT. The OT is setup for 4, 8 and 16ohm cabs via Impedence selector. I used 2 mono SwitchCraft Jacks for the Output jacks and 4 Black Plastic 1/4" Shorting Cliff-Type Phone Jacks for the Inputs...Are these correct? http://i6.photobucket.com/albums/y225/dd3keegs/TweedDeluxe1.jpg http://i6.photobucket.com/albums/y225/dd3keegs/TweedDeluxe2.jpg http://i6.photobucket.com/albums/y225/dd3keegs/TweedDeluxe4.jpg
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: volvo on November 06, 2010, 04:54:29 am: Check input wiring - possible ground fault.

Ampman
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: LooseChange on November 06, 2010, 05:46:15 am: I have had more than one new Switchcraft jack that did not work. The shorting switch did not make contact.
With a none conductive instrument, push the tip of the jack in toward the switch piece and see if it stops.Or just ground the tip and see if it stops.
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: tubeswell on November 07, 2010, 10:34:58 am: Maybe try shortening some of the wiring and shielding the signal cables, including the ones from the PI to the 6V6 grids.
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: sluckey on November 07, 2010, 11:55:06 am: Those cliff jacks should be fine. Do you have them properly grounded? See pic for a good method of wiring those for a Fender amp. Also, I see two toggle switches directly below your preamp. If one of those switches is a power switch, then you have a potential for inducing a lot of 60Hz hum into the preamp stages.

(http://www.el34world.com/charts/images/cliffjacks.gif)
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: eleventeen on November 07, 2010, 02:10:39 pm: Are those switches just under the 12A_7 tubes your power & stdby switches? OMG, I'd be surprised if you didn't get a GIANT amount of hum induced by placing them there. You really can't have those parts in such proximity to gain stages without some serious shielding in place.
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: phsyconoodler on November 08, 2010, 09:40:49 am: I bet the CLIFF JACKS are wired wrong.You will have to use shielded cable with the close proximity to the preamp tubes.

Quote:"4 Black Plastic 1/4" Shorting Cliff-Type Phone Jacks for the Inputs"

Pay attention guys!
Title: Re: Ground Issues on Tweed Deluxe Replica
Post by: dd3keegs on December 14, 2010, 03:29:44 am: Quote from: sluckey on November 07, 2010, 11:55:06 am
Those cliff jacks should be fine. Do you have them properly grounded? See pic for a good method of wiring those for a Fender amp. Also, I see two toggle switches directly below your preamp. If one of those switches is a power switch, then you have a potential for inducing a lot of 60Hz hum into the preamp stages.

(http://www.el34world.com/charts/images/cliffjacks.gif)

Thanks, The Jacks were wired incorrectly. Now to relocate the Power and Standby Switches. Thanks again.