buster
Junior Member
Posts: 73
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Post by buster on Sept 23, 2006 20:51:55 GMT -7
Help! Just bought this amp (used, four years old, near mint condition) and the buzz is insane. (Not volume or master related, or EQ(bass/treb/mids) and no guitar plugged in) Have replaced all the pre-amp tubes, replaced the output tubes one at a time.
Nothing has any effect.... accept these things: a) when the cut and reverb knobs are turned up it gets louder and b) when I removed the reverb tank (wires still attached) and turned it in my hands, the buzz lessened. I checked the wires etc. and they are fine (ie: moving them makes no difference). It was almost as if the tank were acting like an antennae.
Could I have a ground loop? Does this just 'happen' for no reason? It definately sounds like a ground buzz, but my tech says everything looks fine as far as he could see. (Lifted ground, no change).
Ideas? This buzz makes the amp un-useable.
(Note* House grounding is fine, all other amps are no problem).
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Post by billyguitar on Sept 23, 2006 21:15:46 GMT -7
Pull the cables for the reverb all the way out of the chassis?
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buster
Junior Member
Posts: 73
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Post by buster on Sept 23, 2006 23:47:26 GMT -7
Yes I did disconnect the reverb cables from the chassis and the buzzing remains.(So much for that theory I suppose). The cut and reverb controls are still very noisy when turned up, with reverb disconnected from chassis. I never replaced the rectifier tube, by the way, although I tried with two different tubes; A fender 5ar4(made in China) from my deluxe reissue and a new Telsa. The Fender tube caused the fuse to go, and the Tesla didn't even light up. Can't imagine it's the rectifier tube though(my tech said no anyway).
(Thanks for your quick reponse!)
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Post by DRZ on Sept 24, 2006 8:31:33 GMT -7
Buster you can't replace EL-84's one at a time. They need replacing as good matched set or matched quad.( not sure if it's a 18 or 38 ).
If you pull the phase inverter V5 should be a Sovtek LPS, then power up and the hum is still there then IT IS A BAD EL- 84 OR TWO.
If hum is gone with PI out then the problem is in the front end.
But from what you said that Master and Volume make no differance then I would say a new set of WELL MATCHED EL-84's is in order.
Remember guys like a used car, a used amp always needs basic service, it ain't used for nothing.......
DR.Z
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buster
Junior Member
Posts: 73
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Post by buster on Sept 24, 2006 12:06:36 GMT -7
Okay, I pulled the v5 tube in my Maz 38sr and the amp makes no noise at all.
(Thanks again for the quick response)
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buster
Junior Member
Posts: 73
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Post by buster on Sept 25, 2006 20:03:36 GMT -7
So I guess the buzz is coming from the front end although just to recap, the buzz is not at all affected by volume, master, bass, mid or treble controls. Just the cut and reverb knobs. Any suggestions? Note: It really sounds like a ground issue but again, none of my other amps are buzzing so something must be wrong.
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Post by DRZ on Sept 26, 2006 4:13:53 GMT -7
Buster could be a pre-amp tube, could be the reverb tub, or even the RCA jacks connection from the reverb tub, ( big sourse of hum if not a good grounded RCA connection ) .
You buy a 4 year old amp, get it with problems, I would ask the seller what's up. There's only so much troubleshooting that can be done from a CRT screen. You need to see a tech if your repair chops aren't that strong.
DR.Z
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Post by dock66 on Sept 26, 2006 7:46:43 GMT -7
If the problem is still there after you gone through all the possibilities,then box it real well and send it to Dr.Z for a complete tuneup.
dock66
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buster
Junior Member
Posts: 73
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Post by buster on Sept 28, 2006 22:33:41 GMT -7
Thank's for your help everyone. I took the amp to a tech and all he could find (to my chagrin)was a loose tube socket. When I got it home and plugged it in however, the buzz was no longer there. I didn't think a slightly loose preamp tube socket could cause a buzz but that seems to be the case.
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Post by dock66 on Sept 29, 2006 7:51:10 GMT -7
That was an easy fix,keep on rocking.
dock66
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