Noisy Mark III (Solved)

I am starting to notice some crackling sound from my Mark III and it seems like the signal has a bit of fuzzyness to it when I am playing.

No loss of overall power or volume, just the crackling.

Preamp tubes?

Thanks in advance for any info.

My MKIII did same in the second set when I was out playing last night. Fuzzy, farty tone but no loss of volume. All new or recent tubes. It's long over due filter cap replacement as its 30 years old. So I'm suspecting that. It's usually not as cranked as much as it was last night.

Keen to hear suggestions too. I was going to cycle some new preamp valves myself. Usually I can see a visual effect if a power tube is failing and making same fuzzy tone.

It sounds like a tube though or some mucky socket or pot.

I had not thought about a leaky Cap. I may pull the chassis and get the amp going and tap on the caps with the eraser end of a pencil and see if it makes any of them react. Hate to think about replacing the Caps but, I don't want it to get any worse. We also do not have anyone around here who I would trust to know what they are doing. Not going to Guitar Center that's for sure.

Thanks for the idea!

I'm having the same issue with my blue stripe (upgraded from black 20 years ago). I'm lucky enough to live close to the factory, so I dropped it off this morning. I'll pass on what they say, but initial treatment plan is "new tubes and caps, as needed."

Thanks ! I would like to have them rework mine but with the weight of this amp it would be hellish expensive to ship it to them I am guessing. That may be the only thing to do in the end but I ordered a new set of preamp tubes that should be here the 1st of the week so I can trade out a few different ones and see which one has the tone. I picked up a few different Mfg's tubes. I should know what I am facing by next week. I am hopeful its only preamp tubes, I want to keep this amp as original as I can.

Looking forward to some feedback once they get yours going ! 8)

Took mine to Mike B and it was well worth it. Hap complete tune up and recap as well as the 3+ mods. Should last another 30 yrs or so. Hope I do.
=CPW=
PS You can take the amp out of the cab to ship it there if you're too far away. Or... ROAD TRIP TO SF!!!!

Picked mine up from the factory yesterday. Mike B did general maintenance - a few new caps and tubes (as needed), cleaned tube sockets, input jacks and pots. I just did a quick test at home and it sounds great. The real test will come tonight with the band, but preliminary conclusion agrees with cpw, well worth it!

re the OP.. crackling + some fuzziness without volume/power loss - many poss culprits..
P/tubes likely, preamp tubes less likely, a leaky coupling cap poss but not that common, then many other poss causes.

It's chicken or egg whether one chases the actual fault, locates/proves/fixes it.. OR do routine maintenance only to find the fault is fixed in the process..

The pedantic or more thorough method is do the fault first.
Then you KNOW what it was and is fixed..
Rather than fix it with routine maintenance(you think) and have the amp return because symptom returns later and proves U didn't actually fix it in the first place..

For your particular symptoms, I agree cycling pre and power tubes is a good start.
FWIW, your original post took my mind immediately to power tubes.

After that, take line out from fx send - it it fuzzy in the slave amp?
Equally, inject known clean signal into fx return - does it get fuzzy in the boogie ?

Let us know how things progress. regs, Dave

Weak/worn out pre amp tubes.

Thanks for the help !

Thx for the update, and great it was a simple fix - no biasing etc etc.. Gold !!!