Fender Blues Deluxe RI Sound bad

[J. Ignacio]

Hi.
I'm from Argentina.
A close friend has this amp. it starts to trouble. The guitar sounds but has a crackle sound. I will record a video to show your.
Preamp is working right because I use the preamp out and connected to another amp and don't crackle.
Bias voltaje is 10mV. But if i move potbias to max , i only mensure 15mV. So, bias goes 0 to 15mV.
I tried power tubes in my Bassman 5F6a and it sounds good.
D3 1n4006 measure continuity between extremes.
Later , when i come home, i will post power stage voltages.
Any ideas?

[tubeswell]

If it crackles with the old output tubes but doesn’t crackle when you swap the 6L6s in from your Bassman, then I’d say it’s the old output tubes.


Crackling noise is a common sign that output tubes have gone bad. It’s not good to keep on playing an amp with bad tubes - it can damage other more-expensive parts (like transformers)

[stratomaster]

Crackling could mean several things in general and a few more in these amps in particular.

The two biggest reasons I've come across for low/bad output and crackling are dirty preamp out/power amp in jacks and failed PI plate load resistors.

This doesn't mean an the usual reasons for crackling don't apply. Check for intermittent connections, bad tubes, loose sockets, failed IC filter caps (a modern Fender specialty), etc.

It is a bit hard to parse out the rest of your message, but it seems like there's a lot going on with this amp and it will be thorough troubleshooting.

Diode testing for continuity can be tricky, especially in circuit, so that test may not be reliable. I've had occasional luck with the diode testing function of my DMM in circuit. So you can try that. Or alternatively just measure AC on both sides relative to ground.

[8wattjack]

 If this is the new board with the through hole platings, the ribbon cables are almost certainly broken at the solder joints. Take a chop stick and lightly push up on the bottoms of the cables on the tube boards till you get sound.

[8wattjack]

 Caution with these new boards. The solder is what makes the cables hard and break so easy. Being now through hole the solder wicks deeper into the wires. They WILL break upon first removal and even just vibrations from playing. I carefully run a bead of silicone on all the ribbons a day in advance before pulling the board.

[J. Ignacio]

If it crackles with the old output tubes but doesn’t crackle when you swap the 6L6s in from your Bassman, then I’d say it’s the old output tubes.

Thanks for answer.

No. I use the Fender Deluxe tubes in my bassman and works fine. Then i try the bassman tubes in Deluxe and crackle persist.

Crackling noise is a common sign that output tubes have gone bad. It’s not good to keep on playing an amp with bad tubes - it can damage other more-expensive parts (like transformers)

[J. Ignacio]

Caution with these new boards. The solder is what makes the cables hard and break so easy. Being now through hole the solder wicks deeper into the wires. They WILL break upon first removal and even just vibrations from playing. I carefully run a bead of silicone on all the ribbons a day in advance before pulling the board.

Thanks for answer.
I Will check that.

[tubeswell]

No. I use the Fender Deluxe tubes in my bassman and works fine. Then i try the bassman tubes in Deluxe and crackle persist.

Then it’s not the output tubes.


 The Hotrod and Blues Deluxe amps are notorious for faults from poor design, including general stuff other posters have mentioned, as well as problems with the low voltage power rail that powers the transistor/op amp circuits and the relays, which when it fails can cause parts damage that results in all sorts of noise getting into the signal path. The 5W cement resistors in this circuit are mounted right up against the main board and eventually overheat and charr the board, nearby traces and other parts. If you see charring around those, start there.


Popping noises can also be from bad connections, cold solder joints, broken jumper cables and oxidisation on ‘slide-on’ terminal connectors, FX jacks, or loose tube socket pin clamps. Chop-sticking can reveal where loose joints are.

[8wattjack]

Then it’s not the output tubes.


 The Hotrod and Blues Deluxe amps are notorious for faults from poor design, including general stuff other posters have mentioned, as well as problems with the low voltage power rail that powers the transistor/op amp circuits and the relays, which when it fails can cause parts damage that results in all sorts of noise getting into the signal path. The 5W cement resistors in this circuit are mounted right up against the main board and eventually overheat and charr the board, nearby traces and other parts. If you see charring around those, start there.


Popping noises can also be from bad connections, cold solder joints, broken jumper cables and oxidisation on ‘slide-on’ terminal connectors, FX jacks, or loose tube socket pin clamps. Chop-sticking can reveal where loose joints are.
[/quote]

In all fairness the last two I looked at had bad output tubes also. They both were the newer design with through hole plated boards and factory tubes. I am just now seeing these newer ones like this and only the blues deluxe. Yes they are through hole plated. Fixed one set of problems and created a new one. They did lift the 470ohm resistors off the board on these, but there was still some discoloration so I did the updates as usual. The ribbons snap RIGHT OFF like a potato chip! If it is setting at 15 ma its likely the tubes are bad as well, just not the source of the crackling. Has anybody else worked on the new boards that are through hole plated? Heads up if not! Also solder wick takes forever to desolder these. Best to get a pump!

[J. Ignacio]

Here is

47uf x500v has a little oil/hot charge in + size.

[tubeswell]

Thanks for uploading the clip, but you mostly pointed your camera at the tubes and we couldn’t get a close look at the main board to tell if the wire-wound resistors had been lifted or not.


If the filter caps are discharging gunk, they need replacing. Those Illinois Caps are junk anyway. The transistor and opamp power supplies could very well be affected by low voltage power supply problems - which is a likely cause of the distortion problem.

[J. Ignacio]

Tomorrow i will record a new video.

Tubes are ok. Power and preamp.

I dissamblied the principal board and check all the solders. Pots, relay, Jacks, IC. Also cables between boards
I do the same with tube board. Everything looks ok.

When i turn off the amp. Electrolitic capacitor discharge very fast. It's automatic.
Go from 378v to 0v so quick

Voltage
Voltage at junction R59 and R60 : -48V.
R61: 377v
R62: 377v

D15 junction with c43 i measure -127mv. Schematic say -48mv

Maybe C43 is death? Not look like it