Blues Jr. Help

[treyhaislip]

I highly recommended a Blues Jr. to my cousin and he bought one–loved it BUT I get a call from him that the other day he turned it on and heard a loud pop and now the amp hums and sounds distorted. He checked all of the tubes (going through BillM's troubleshooting page) and the hum is still there. The guitar sounds distorted at all volume levels, there is crackling and fissing as well.

Any thoughts?

 

[Lake Placid Blues]

Re: Blues Jr. Help

Might be something in the power supply. It will require a proper diagnose by a tech.

 

[blueman335]

Re: Blues Jr. Help

Note to self: Don't be in a big hurry to recommend a Blues Jr to anyone. At least not until this thread gets things sorted out.

 

[treyhaislip]

Re: Blues Jr. Help

Might be something in the power supply. It will require a proper diagnose by a tech.

I agree that it should be diagnosed by a good amp tech–my cousin is in Texas and I'm in Georgia. lol

In high school he worked at an electrical repair shop, went to school where he was trained in avionics so he does have a solid background in electric repair BUT I still recommend he take it to an amp tech...I just didn't know if someone else had a similar issue with Fender Tube amps that is a relative easy fix.

Note to self: Don't be in a big hurry to recommend a Blues Jr to anyone. At least not until this thread gets things sorted out.

Just because one used Blues Jr has an issue? :33:

 

[blueman335]

Re: Blues Jr. Help

Just because one used Blues Jr has an issue?

Humor, son, humor.

 

[Lucy Diamond]

Re: Blues Jr. Help

Is it new??

Bring that $h!t baaaaaack man!!!

 

[Funkfingers]

Re: Blues Jr. Help

Bill M's troubleshooting page only really describes a simple process of elimination by substitution to identify faulty pre-amp stage valves (tubes). He says nothing about output stage valve substitution. Has this been tried? You might also want to check over the output transformer and the loudspeaker coil.

I concur with the recommendation to have a qualified amp tech perform this work.

 

[treyhaislip]

Re: Blues Jr. Help

Is it new??

Bring that $h!t baaaaaack man!!!

Nope, its a used one–several years old.

Bill M's troubleshooting page only really describes a simple process of elimination by substitution to identify faulty pre-amp stage valves (tubes). He says nothing about output stage valve substitution. Has this been tried? You might also want to check over the output transformer and the loudspeaker coil.

I concur with the recommendation to have a qualified amp tech perform this work.

I agree, time to take it to an amp tech. I was just wondering if anyone had this issue or something similar.

 

[Lake Placid Blues]

Re: Blues Jr. Help

My experience with "crackling" and "distorted at all levels",... with my own amps has always been something beyond a bad tube or tubes that can be fixed by the user by simply swapping tubes and such. This is why I was quick to recommend a tech. In one case it was a bad cathode cap. In another case it was it was a broken solder to a filter cap after it fell out of a truck. In another case it was a bad rectifier tube (It doesn't have a tube rectifier does it?). A bad rectifier will eventually blow the mains fuze, perhaps serially. Another case it turned out to be a bad pot (the presence knob). But do check the power tubes if you haven't already. A red plated or cold power tube may manifest some of those symptoms, but it usually blows the HT fuze rather quickly.

 

[Gone_Shootin]

Re: Blues Jr. Help

Like others have said, it could be any number of things. I would start by trying a known good 12AX7 in each preamp position, along with the phase inverter hole. If that doesn't work, I would try a known good set of EL84s in the poweramp. If that doesn't work, then I would pull the chassis and look around for bad components and bad solder joints. And since it's used, it wouldn't be a bad idea to look over the caps anyway.

 

[Gone_Shootin]

Re: Blues Jr. Help

My experience with "crackling" and "distorted at all levels",... with my own amps has always been something beyond a bad tube or tubes that can be fixed by the user by simply swapping tubes and such. This is why I was quick to recommend a tech. In one case it was a bad cathode cap. In another case it was it was a broken solder to a filter cap after it fell out of a truck. In another case it was a bad rectifier tube (It doesn't have a tube rectifier does it?). A bad rectifier will eventually blow the mains fuze, perhaps serially. Another case it turned out to be a bad pot (the presence knob). But do check the power tubes if you haven't already. A red plated or cold power tube may manifest some of those symptoms, but it usually blows the HT fuze rather quickly.

Blues Jrs are solid state rectified.

 

[treyhaislip]

Re: Blues Jr. Help

My experience with "crackling" and "distorted at all levels",... with my own amps has always been something beyond a bad tube or tubes that can be fixed by the user by simply swapping tubes and such. This is why I was quick to recommend a tech. In one case it was a bad cathode cap. In another case it was it was a broken solder to a filter cap after it fell out of a truck. In another case it was a bad rectifier tube (It doesn't have a tube rectifier does it?). A bad rectifier will eventually blow the mains fuze, perhaps serially. Another case it turned out to be a bad pot (the presence knob). But do check the power tubes if you haven't already. A red plated or cold power tube may manifest some of those symptoms, but it usually blows the HT fuze rather quickly.

Personally I don't go poking around in electronics–unfamilar territory and I don't mind paying a qualified tech to do quality work on an amp. I don't mind swapping a pre-amp tube but that's about it for me.

My cousin has worked with electronics quite a bit so he is more comfortable (and experienced) working on electronics so I thought I'd ask to see if it was something he could at least trouble shoot.

Thanks for the info!

Like others have said, it could be any number of things. I would start by trying a known good 12AX7 in each preamp position, along with the phase inverter hole. If that doesn't work, I would try a known good set of EL84s in the poweramp. If that doesn't work, then I would pull the chassis and look around for bad components and bad solder joints. And since it's used, it wouldn't be a bad idea to look over the caps anyway.

Ha! Yup, definitely could be a number of things, tubes themselves are not the problem (still exists when the tubes are out.)

I haven't heard back from him but I suggested looking over the soldering joints, my 95 Hot Rod Deluxe was noisy when I got it (used) and had the soldering joints redone by a local amp tech and it is super quiet now (previous owner had already upgraded the caps.)

Thanks for the info!

Blues Jrs are solid state rectified.

Yup, solid state