Blues Deluxe breakdown

[Eddy Sea]

Hi...  I have a Fender Blues Deluxe Reissue amp. I bought it used. I think it’s about 7 years old but it looks brand new. Best sounding amp I’ve ever owned - I like it a lot. But when I hit a G or an Ab, it goes nuts. Starts crackling and buzzing like crazy. I’ve had it in to a certified Fender repairman. He hasn’t been able to nail down the problem. Anyone experience the same problem? Know the secret?

[ezbass]

First up  

 

As to your problem, that’s a head scratcher As it seems to be activated by particular notes, I’m wondering if it’s a loose connection type of thing where the frequency of the note is causing the connection to disconnect and make with the waveform. Your tech should be able to trace it eventually but it may take time (I used to be a repairman for office equipment and intermittent faults are a PITA).

[Dad3353]

6 hours ago, Eddy Sea said:

...when I hit a G or an Ab, it goes nuts. Starts crackling and buzzing like crazy...

So... Play in 'E' like everyone else. 

No, seriously... Try connecting the amp to a different speaker (disconnect the current speaker, temporarily wire up another cab...), just to see if it's the speaker freaking out or the amp. If it's the speaker: change it for another. If it's the amp: a bit more difficult to trace, but a good tech should be able to. Try tapping the chassis to see if there's a loose contact, same on the soldered joints, to see if there's a dry one (don't do this yourself, unless qualified to work on potentially lethal equipment...). I'll assume that the valves have been swapped out, one by one, because that's an obvious source of problems of the sort..?
Once fixed, t'would be good to get news here; it could help others. Good luck with it; it's a fine amp. 

[Stub Mandrel]

Fixed a buzz like that on a Vox amp once. Unclipped each valve in turn and wiggled it in its socket...

Could also be a valve with something loose inside.

[Kiwi]

I agree, definitely sounds like something loose aboot the hoose.

[leftybassman392]

I had a similar buzz from my Cornford at exactly the same frequency. After checking that everything was screwed down properly, I concluded that a microphonic valve was the source of the problem. (Remember that 50Hz is mains AC voltage, which in pitch terms is between G and Ab.) Replacement of the preamp valves at my local emporium fixed the problem. I was selling the amp anyway as it happened so I reasoned that I might as well get them all changed, but the method below should work.

The BDL appears to use 12AX7's x3 in the preamp, which is fairly standard. Get a new valve (you can buy them at pretty modest cost online), and swap out a preamp valve with the good one, switch on and play, switch off and continue in the same vein with the remaining valves until the problem goes away.

There could be a problem with the mains transformer (I've had issues with transformers in a Fender reissue amp in the past), but I'd be surprised if you need to look further than the valves.

Hope this helps.