I've seen a few mentions in different threads about noise in a tube amp coming from noisy plate resistors. Is there a specific type of resistor that gets noisy with age? Is there a good way (short of replacing the resistor) to see if this is a problem? I was thinking a cap tacked in parallel with the resistor might be a way to troubleshoot without removing parts, maybe can be done without removing a circuit board. Thoughts?
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Originally posted by glebert View PostI've seen a few mentions in different threads about noise in a tube amp coming from noisy plate resistors. Is there a specific type of resistor that gets noisy with age? Is there a good way (short of replacing the resistor) to see if this is a problem? I was thinking a cap tacked in parallel with the resistor might be a way to troubleshoot without removing parts, maybe can be done without removing a circuit board. Thoughts?
So it's clear, that Deluxe was the first of many, now hundreds & possibly thousands, Fenders I encountered that turned out to have this problem. Sure, funky old resistors can do it but they're by far not the only culprits. Even wire has sometimes turned out to be the noise source. Not what we might expect but that's what it turns out to be on occasion.Last edited by Leo_Gnardo; 02-11-2021, 11:01 PM.This isn't the future I signed up for.
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Originally posted by g1 View PostWith noisy resistors, applying heat or cold will sometimes affect the noise.
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Originally posted by Leo_Gnardo View Post
That's what I thought, until one fine day many years (40-ish) ago I replaced every resistor in a nice old Deluxe Reverb, and many of the caps besides. Hiss, crackles, sizzles, squeeks & pops persisted. It was the dam' board! So... before you embark on a similar journey, keep in mind that black cardboard used in Fenders, some other amps besides, and much to the chagrin of kit builders, even in current kits offered by otherwise trustworthy outfits. Corroded tube pins & sockets can contribute to noises also.
So it's clear, that Deluxe was the first of many, now hundreds & possibly thousands, Fenders I encountered that turned out to have this problem. Sure, funky old resistors can do it but they're by far not the only culprits. Even wire has sometimes turned out to be the noise source. Not what we might expect but that's what it turns out to be on occasion.
So true.
Just worked on an Ampeg with corroded brittle wiring that was the cause of intermittent snaps, crackles and pops.
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Keep this in mind: statistics do not apply to individuals. You might find that carbon comp resistors are more likely to go noisy than some other type, but by the same token there are plenty of old amps with 60 year old carbon comp resistors that did not go noisy. And to reinforce the above stories, please don't replace all the carbon comps in some old amp "so it won't get noisy".Education is what you're left with after you have forgotten what you have learned.
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I've had quite a few amps for repair with metal film resistors that went noisy. I fixed a brand-new amp for another builder under warranty that was built be low noise with metal film resistors and the first tube had a noisy plate resistor. The newer MF types don't seem to be as good as they used to be.
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If it is Fender product, replace them with 1W MO. You will never see it again for the same complaint.
I keep a stock of 100k, 91k and 82k 1W MO.
Also for the Blues Juniors, replace both G2 feed resistors, when the EL84s have expired, use 0.6W MO. MO are fire proof, act like a fuse and won't burn out the board.Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
If you can't fix it, I probably can.
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MEF team.... not to complicate the matter, but the timing of the post and replies comes just after I too looked into the subject of resistor types. I found this article on the Aiken Amplification Web site - Resistor Types - Does It Matter?
If nothing else, it makes for interesting reading for those of us who are perpetual students of amp design and maintenance.It's not just an amp, it's an adventure!
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There is nothing more valuble than personal experience.
I have 50 years of it and enjoyed the steep learning curve from time to time and worked with manufacturers to ensure the correct component was fitted for BEAB and HSE regulations that ensured the products met all if not exceeded the safety standards required by EU countries.Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
If you can't fix it, I probably can.
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