Problem ;-(

gasket

gasket

Ambassador of the Guitarded
Problem with my Fender Blues Junior.
This afternoon while practicing I noticed a couple of strange crackling noises, not overly loud and only happened twice over an hour. Come back to it tonight and as soon as I turn on I'm getting a nasty pop type noise backed up by a rattling static type of hum. Naturally I turn off straight away, tested again 2 min later and same result.
Any suggestions before I take it to our local (respected) amp specialist?

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Do you have spare power valves? Matching EL84s, if you have a set. If you have just one spare, roll it into V4, the V5, to see if the problem is resolved.
My guess is that one of these has gone bad, which is completely normal, and something you can easily fix without the need of an amp tech.
 
Goldmember said:
Do you have spare power valves? Matching EL84s, if you have a set. If you have just one spare, roll it into V4, the V5, to see if the problem is resolved.
My guess is that one of these has gone bad, which is completely normal, and something you can easily fix without the need of an amp tech.
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Thanks. No spare valves but happy to buy one or a set if the symptom SOUNDS LIKE OR SUGGESTS a bad valve.
When it was new I had a noise that I fixed after advice. Was told to slightly rotate the top of valves while pins still full socket into amp. I guess that was correcting possible bad contact. I don't want to put my hand in there when it has only just turned off, I've heard it takes time for stored power to dissipate, you can get a shock if recently turned off. Don't know if true but better to be safe.
I just tested again with no guitar or lead attached and the problem is still there.
 
gasket said:
Thanks. No spare valves but happy to buy one or a set if the symptom SOUNDS LIKE OR SUGGESTS a bad valve.
When it was new I had a noise that I fixed after advice. Was told to slightly rotate the top of valves while pins still full socket into amp. I guess that was correcting possible bad contact. I don't want to put my hand in there when it has only just turned off, I've heard it takes time for stored power to dissipate, you can get a shock if recently turned off. Don't know if true but better to be safe.
I just tested again with no guitar or lead attached and the problem is still there.
Click to expand...
CAUTION. Amps can retain LETHAL voltage for days or weeks. To be safe, you should manually discharge any capacitance ONLY IF YOU ARE COMFORTABLE DOING SO. Then check and then double check it is discharged. Then be cautious anyway. There are many YouTube videos on this. PLEASE BE VERY CAREFUL
 
Cheers Ray.
I just googled my problem and found a vid of a bloke with same problem. Vid showed a valve arching and making noise. When I looked through the rear grill and turned mine on ... BINGO looked and sounded exactly the same. I suspect I require two power valves?
I also suspect I can change them safely without touching any other component and therefore not get zapped ???
 
gasket said:
Cheers Ray.
I just googled my problem and found a vid of a bloke with same problem. Vid showed a valve arching and making noise. When I looked through the rear grill and turned mine on ... BINGO looked and sounded exactly the same. I suspect I require two power valves?
I also suspect I can change them safely without touching any other component and therefore not get zapped ???
Click to expand...
I am confident you can safely remove the power valves. Just be cautious when dealing with the interior of the amp or socket contacts.
 
RVA said:
Just be cautious when dealing with the interior of the amp or socket contacts.
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Will do!
Checking out for the night now but before I go another question, will check comments in about 8 hours.
I'm a novice learner / player. Now and into the near future small variations in tone quality don't worry me much. Naturally I can hear rubbish but for now I'm not seeking that elusive something. So are there any common valves I should avoid? Or others priced reasonably that I should look for?
 
Yeah, sures sounds like power tubes/valves to me. Easy thing to switch. If you don’t wanna have to muck with the bias (and open the amp up) buy Fender-branded output tubes that have the same color prining on them as your originals. They will be blue, white or red depending on factory bias.
 
If you suspect tubes an easy check is to power up the amp with the back cover off and then tap each tube lightly with a light wooden stick or chop stick sort od object. When you tap the bad tube you will hear it.

This is a common troubleshooting procedure in all shops.
 
There's no reason why your hands have to touch anything that can lead to electric shock if all you're going to do is handle the tubes.
Culprit could be the power tubes. It can also be any of the preamp tubes, too. Check them all. You should always have a spare 12AX7 and a spare set of EL84s for your Blues Junior.
Depending on the design of the amps circuit, a bad power tube could eventually cause damage to other parts of the amp.
If one of the power tubes is bad, replace both as a match set.
How old are all the tubes in your BJ?
You might as well replace the 12AX7/phase inverter tube, even if it checks out OK, and save that one for a spare.
For some extra preventive maintenance, get some contact cleaner like DeoxIT and spray the pins of the tubes and the tube sockets and let them have some sex with each other. The cleaning solution should evaporate quickly, but you can give the parts a nice blow job just to be sure.
 
Ya be careful.
Swapping or changing tubes is pretty standard stuff but you must heed any output tube biasing considerations.

It is good practice to have known good spares to swap in as another basic troubleshooting technique.
When I bought some NOS tubes recently, I kept my existing tubes for this purposes.
And that is what I told myself as I clicked "Buy it Now". LOL.

The tap test for is also good for diagnosing functional but whiney biotch (microphonic) tubes; especially pre amp tubes.
using the eraser end of a pencil sometimes allows you to hear the tube complaining more clearly because of the dull thud of the eraser vs the clack of the wood against her glass envelope. Yes I did.

One of the sounds I have heard almost is like the glass of two beer bottles being rubbed together -hard to put into words.
But, it was easier to hear with the dull thud of the eraser than the sharper clack of the wood.
 
gasket said:
So are there any common valves I should avoid? Or others priced reasonably that I should look for?
Click to expand...

Any of the major brands of currently produced tubes are fine; this is tonewood debate territory: highly subjective.
As long as you use the same model tube. There are some substitutions that are ok but that is a different topic all together.
I am not an old hand at this either but am currently using tubes from JJ, Tung Sol, Electro-Harmonix, with no complaints.
I use the less expensive models, and also as more a beginner than seasoned player, dont feel I am short changing myself on tone.
But these words just reflect my experiences.

I have used China no brand EL84 that sound ok but not as good as others, I have Sovtek 12ax7 that came in my Silkyn that sound muffled compared to the JJ I put in at V1 - wet blanket kind of thing.
But only at V1 did it make a really noticeable difference. I thought just that one tube was a dog, but it sounds ok in my tweed champ clone.
Not great but ok. It is mainly a known good spare rank for now.

Many of these "brands" you see are just private branding, are all made from the same few factories in Eastern Europe or Asia.

I dont even mean like different models of different brand guitars made at the same factory, I mean the same tubes coming off the same machines into boxes with different labels.
 
Thanks all for comment so far.
Last night when the amp failed (made real bad noise) I'd had a big day, I wasn't as sharp as I should have been. The vid I watched after my second post has this 99.9% nailed down as a bad power valve, Just as in the vid I can see bolts of lightning zapping about within the glass. I'll have this sorted today or if parts are not available quickly at least have them ordered.
Chili's vid was a good introduction to safety. Tomorrow (by chance) a friend will be visiting, he has an electronics background and I know many years back he built amps for musical friends.
I'll post the outcome and don't expect anything other than a positive result.
 
gasket said:
Thanks all for comment so far.
Last night when the amp failed (made real bad noise) I'd had a big day, I wasn't as sharp as I should have been. The vid I watched after my second post has this 99.9% nailed down as a bad power valve, Just as in the vid I can see bolts of lightning zapping about within the glass. I'll have this sorted today or if parts are not available quickly at least have them ordered.
Chili's vid was a good introduction to safety. Tomorrow (by chance) a friend will be visiting, he has an electronics background and I know many years back he built amps for musical friends.
I'll post the outcome and don't expect anything other than a positive result.
Click to expand...
Glad to hear that the problem has been well identified! Fear not the replacement of valves!
It sounds like a good time for maintenance on the Blues Junior.
This is a good thing. Why not replace all preamp and power valves
at this time, and dig it? ;)
 
Now 1:00PM Thursday (the day after the amp failure).
Wanted to do this job myself so started the day ringing around music shops and then electronics places, no EL84s in town, that's total BS :-(
Gave up and called the amp specialist in my area (20 min drive away). Yep he has them in stock, happy to sell BUT asked me to bring it in and he'll give it the once over and fit free.
Just back, the story, Blues Jnr doesn't have adjustable bias. He changed a capacitor, fitted new tubes, tested with a scope and a guitar. Finished by trimming the knob shafts so the bushings are now sitting in the body supported correctly and charged me $20 plus the tube cost.
I'm happy and a little more educated.
Again thanks for TTR input :-)
 
gasket said:
Now 1:00PM Thursday (the day after the amp failure).
Wanted to do this job myself so started the day ringing around music shops and then electronics places, no EL84s in town, that's total BS :-(
Gave up and called the amp specialist in my area (20 min drive away). Yep he has them in stock, happy to sell BUT asked me to bring it in and he'll give it the once over and fit free.
Just back, the story, Blues Jnr doesn't have adjustable bias. He changed a capacitor, fitted new tubes, tested with a scope and a guitar. Finished by trimming the knob shafts so the bushings are now sitting in the body supported correctly and charged me $20 plus the tube cost.
I'm happy and a little more educated.
Again thanks for TTR input :)
Click to expand...
Dig it.
 
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