Intermittent, volume independent crackle on Fender Deluxe Reverb (w/ mp3)

[spiral]

I have a 72 Deluxe Reverb which i have had for years. I recently replaced the power filter caps and got a new set of tubes. I am having an issue with what sounds like gurgling static. It is intermittent, the volume and tone has no effect (ie. volume at 0 and static still present), it is a fairly low level, playing doesn't affect it, it only appears about 5-10 minutes after the amp has warmed up, and it goes away when the amp is on standby.

I have started swapping preamp tubes but since it only appears when it has warmed up, it is taking forever. I am starting to suspect it might be the power tubes (i hope!). I was hoping that if someone heard the static it would be a dead giveaway so i am posting a sound sample.

http://www.polishoperative.com/junk/FenderDR_static.mp3

Thanks!

[trem]

Did you replacing the old, 100k plate resistors with 1 watt carbon film?

[spiral]

Yes. I replaced those resistors. Is that what it sounds like? Maybe i fried the new ones when i was soldering?

[spiral]

Did you replacing the old, 100k plate resistors with 1 watt carbon film?

After i posted i started digesting what you said. I replaced the resistors across the filter caps, but i didn't replace resistors anywhere else.

[R.G.]

Start pulling out preamp tubes from the first one and progress toward the power amp. When you hit a tube which makes this vanish, you are either in or immediately past the stage which is generating the sound, as pulling a tube prevents it from passing along any input.

If tone and volume have no effect, it's either in or past the tone/volume parts.

Always remember:

Divide and Conquer

[spiral]

And i can safely do this (ie. electrically; i know they will be hot) while the amp is on? And it is ok to run the amp sans-tubes?

[Zouto]

Well, it sounds to me a bit like classical vintage carbon comp fry and/or cold solder.Check solder points, (filter cap etc...) grounds, and take 2 Watt metal oxide resistors for plates for some great reliable and crackle'n'hassle free sound.
Good luck
Zouto

[Albert Kreuzer]

And i can safely do this (ie. electrically; i know they will be hot) while the amp is on? And it is ok to run the amp sans-tubes?

Yes, it's safe. But it will make a loud pop when you pull a tube. Before you put them back in, better turn off the amp.

Cheers,
Albert

[spiral]

Yes, it's safe. But it will make a loud pop when you pull a tube. Before you put them back in, better turn off the amp.

Ok. Thanks for the reassurance. I have read that elsewhere but wanted to make triply sure.

Well, it sounds to me a bit like classical vintage carbon comp fry and/or cold solder.Check solder points, (filter cap etc...) grounds, and take 2 Watt metal oxide resistors for plates for some great reliable and crackle'n'hassle free sound.

Yes. It it seeming that way. I pulled all the preamp and phase inverter tubes and the crackles are there. So just the plate resistors it sounds like? I know carbon vs. modern becomes a religious debate, but is it better to just replace all the resistors with metal oxide in one shot?

[spiral]

Well, it sounds to me a bit like classical vintage carbon comp fry and/or cold solder.Check solder points, (filter cap etc...) grounds, and take 2 Watt metal oxide resistors for plates for some great reliable and crackle'n'hassle free sound.

For those that guessed the bad plate resistors: you win a prize. unfortunately that prize is a crackle-free amp at my house so you will have to enjoy it in your mind or come to chicago and i will play you some major scales and diminished chords over a beer.

I replaced out the 4 plate resistors for both channels and also upped the 3 16uf 450v power supply caps (they were new from when i Blackfaced the amp a few months ago, but i have 20uf 500v volt ones and decided to just replace them based on recos from another thread) and the static / crackle is gone. So it was either a bad solder joint on one of those things or bad resistors.

I tested all the resistors and they were spot on, but i assume they start to go open when they heat up?

Thanks again for everyone's reply. My old amp is slowing getting young again.

[Jazz P Bass]

Carbon Comp

If you look up carbon comp data sheets, there is an actual "Noise" figure.
Compared to metal it is high.
As an aside, some people figure the carbon comps give an amp Mojo.

[Zouto]

Ok. Thanks for the reassurance. I have read that elsewhere but wanted to make triply sure.

Yes. It it seeming that way. I pulled all the preamp and phase inverter tubes and the crackles are there. So just the plate resistors it sounds like? I know carbon vs. modern becomes a religious debate, but is it better to just replace all the resistors with metal oxide in one shot?

Yeah, I did it on all of my amps, even those sacred vintage ones, with best results, NO VINTAGE MOJO LOST (amps smell like before), only better (more) sound with less crackle and hiss.Absolutely no sterile or cold tones, all of my friends like it, so I restored their amps too with metal oxide and metal film resistors like mine.
Zouto

[spiral]

Yeah, I did it on all of my amps, even those sacred vintage ones, with best results, NO VINTAGE MOJO LOST (amps smell like before), only better (more) sound with less crackle and hiss.Absolutely no sterile or cold tones, all of my friends like it, so I restored their amps too with metal oxide and metal film resistors like mine.
Zouto

I wish i had the parts to do it all at once but i only had the 4 i needed for the immediate fix. Which types did you use where (ie. metal oxide vs. metal film)? From what i read, the carbon comp resistors only matter most on the plate resistors, everywhere else you are just trading for more noise. Thanks for the reply.

[Prairie Dawg]

For those that guessed the bad plate resistors: you win a prize. unfortunately that prize is a crackle-free amp at my house so you will have to enjoy it in your mind or come to chicago and i will play you some major scales and diminished chords over a beer.

I replaced out the 4 plate resistors for both channels and also upped the 3 16uf 450v power supply caps (they were new from when i Blackfaced the amp a few months ago, but i have 20uf 500v volt ones and decided to just replace them based on recos from another thread) and the static / crackle is gone. So it was either a bad solder joint on one of those things or bad resistors.

I tested all the resistors and they were spot on, but i assume they start to go open when they heat up?

Thanks again for everyone's reply. My old amp is slowing getting young again.

Carbon comp resistors are prone to this sort of misbehavior. I recently scored a box of 1,000 100k carbon film resistors for just that reason.

[Zouto]

I wish i had the parts to do it all at once but i only had the 4 i needed for the immediate fix. Which types did you use where (ie. metal oxide vs. metal film)? From what i read, the carbon comp resistors only matter most on the plate resistors, everywhere else you are just trading for more noise. Thanks for the reply.

For high voltage appliance (plates etc.)I use 2Watts, 5% metal oxides for lower voltages (cathodes etc.) I use 0.25Watts, 1% metal films, even when playing no metal at the moment.BTW, it's good to check those coupling caps too.
Zouto