Help Needed! Fender Blues Deluxe Reissue making all sorts of noises.

marcus449

As the title states I've got a Fender BDRI. 

Accidently left it on standby for a few days (not that big of a deal) and came back to it making horrible noises when turned on and played. I've quickly replaced the power tubes with like for like as I thought they might have gone but that has done nothing to help the problem (was praying for a quick fix and need the amp for next week)

I've tried all the variables; different guitar, different cable, different power source etc

Here are 2 videos to aid some sort of online diagnosis if possible. 

Amp turned on (a fair bit of hum/buzz):

https://youtu.be/0ljYkmiwfdU

Amp turned on and playing (hum/buzz and a crunchy sound when notes are played):

https://youtu.be/oxMXRSNUldQ

At the moment the only anomaly I can see is this white matter around the power tube solder joints:



Anyone with any thoughts?

ICBM

Have you tried changing the preamp valves? If you don't have any spares, just swap them around and see if the fault changes - if it doesn't, it's unlikely to be a valve.

I can't watch the videos right now, but a common fault with these is a failed filter cap, usually the one under the input jacks - that will cause hum, sometimes odd distortion, or 'motorboating' on the drive channel - if it does that, it's a near certainty.

The white residue isn't anything to worry about.

marcus449

@ICBM yes, forgot to mention I bought a new pre-amp tube and tried swapping it out, didn't help!

Yeah I'm taking it onto the bench on Monday to get it looked at as over the phone the mentioned the same filter cap as a potential source of the problem!

Much appreciate the input!

richalderandash

Could be a number of things.  If the tubes were running hot - likely, as most Fenders do - you could have cooked any number of parts.  The control grid resistors, coupling caps and even the IT could fail under continued heat.

The white matter is a little concerning.  That makes me think the PCB has failed and become conductive.  This happens in the Marshall JTM and JCM range a lot.  You end up with a short between the control grid (a neg voltage circuit, around -35 to 50V) and the screen grid (a pos circuit, around 350-450V). Obviously a short here wouldn't be good!

If you're comfortable with a DDM, unplug the amp, take the tubes out, and test the resistances between each pin.  On a EL34 / 6L6, the main focus is between pin 4 and 5.  If should be OL / no reading.  If there is any resistance - even 20M ohms - get a tech to drill out the PCB to isolate one or the other.

DJH83004

As per ICBM, first port of call would be a failed filter cap, basically the last one in the chain smoothing the pre-amp section, is the usual suspect with the noise. regarding the gunge around the valve base, it doesn't look like anything is tracking (from the underside of the board), did someone spill a pint over it in a previous life I would give it a good clean and re-solder the joints just as a matter of course, but suspect your problem lies elsewhere, (worth checking the bias voltage whilst you are at it).