# Noise in Fender "Normal" channel...



## StevieMac (Mar 4, 2006)

I'm sure it could be a dozen or more different problems but just thought I'd ask. Only have noise in a DR when I turn up the Volume on the Normal channel. Some hiss but mostly a static-like sound which starts as soon as it's past 1 but also stops(?) at 10. No unusual noises in the Vibrato channel, when any other pot is turned, or while wiggling any of the tubes. 

Start by swapping out the Normal channel (rightmost) preamp tube? Bad pot maybe? Actually, the sound reminds me of what I heard in my brown Pro when some of the screen resistors needed replacing (crackling). Could this occur on one channel only? 

Anyway, was hoping to try some simple (not potentially lethal) troubleshooting before sending it in...


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## StevieMac (Mar 4, 2006)

Update: 

The good news: Discovered that preamp tube in the Normal channel was "bad". Replacing it with a good tube reduced hiss/noise ALOT. 

The bad new: The faint static/crackling sound is still there and more apparent now that the aforementioned noise is gone.

The static is noticeably reduced when either channel's preamp tube is pulled??? Screen resistors need replacing?


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## Wild Bill (May 3, 2006)

StevieMac said:


> Update:
> 
> The good news: Discovered that preamp tube in the Normal channel was "bad". Replacing it with a good tube reduced hiss/noise ALOT.
> 
> ...


It can't be the output tubes if the problem is in only one channel. And preamp tubes don't have screen grids! They're triodes. They only have a signal grid.

You might have a noisy plate resistor. The 12AX7 is two separate triode tubes in one bottle of glass. There will be a plate resistor at pin 1 and pin 6. If they are carbon comps they almost certainly will be causing your problem! Best noise/static generators ever made! Replace 'em with carbon film or better yet, metal oxide 1 watt power resistors.

VERY quiet!

If this doesn't fix the problem try reheating all the solder joints for the associated parts around the Ch2 tube.

WB


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## StevieMac (Mar 4, 2006)

Lol...shows how little I know! I confused "screen" with "plate" but knew that _some_ resistors off the preamp tubes had made similar noise in my brown Pro. 

Thanks for correcting and re-directing me Bill!

Steve


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