Tube replacement hep
- Thread starter Clint 55
- Start date
SlyFoxx
Glossless
Look for signs of a bad heater (no orange glow) and or discoloration from overheating. Some amps come with extra tubes in the guise of extra circuitry that runs on tubes like reverb or trem. A swap and get an amp back in business albeit now without reverb etc but confirms where the bad tube was. But since you're asking this question my best advice is to get help from somebody who knows stuff and can be in the same room as the amp.
Gtrjunior
New member
Does the amp still power on?
Many times when a tube blows it takes the fuse with it. Or more accurately the fuse does it’s job and prevents a surge from damaging another component.
If it is blown (fuse) you’ll need to replace the power tubes. You should replace them as a matched set and not just stick another tube in there. And depending on what all you’ve got you need to bias the tubes.
Let me know what you’ve got happening.
JMP/HBE
Well-known member
Blown fuse is a sign of another problem and if it is blowing fuses or tubes just replacing those won't necessarily fix the original problem you'll just keep blowing fuses & tubes which is costly.
Kinda like trying to cure lung cancer by smoking more tobacco.
Gtrjunior
New member
Not true at all.
I suddenly blew a tube in my Quickrod. It took the fuse with it. I replaced the fuse and it blew again.
I then replaced the tubes and biased the amp. Put a new fuse in it and it has worked perfectly for going on 3 years now.
It’s common knowledge that a bad tube can absolutely pop a fuse.
beaubrummels
Well-known member
I've had "cragley sound then nothing" be tubes, fuses, transformers, caps and heat damaging wires, traces, joints etc. So.. those are the things I might be looking at.
JMP/HBE
Well-known member
Well with no pics / vid or other INFO its like trying to diagnose a brain tumor on a forum but knock yourself out Ripley.
The whole purpose of a fusable link is to protect components and prevent a meltdown.
Go ahead and throw another quad of power tubes in there @ $225 per and "see what happens".
Or ..... you could just take it to a qualified tech, call me old fashioned.
The whole purpose of a fusable link is to protect components and prevent a meltdown.
Go ahead and throw another quad of power tubes in there @ $225 per and "see what happens".
Or ..... you could just take it to a qualified tech, call me old fashioned.
Clint 55
OH THE DOUBLE THICK GLAZE!
Hi thanks for the replies everyone. I see what you're saying. It could be the tubes but you don't want to just throw money at it because sometimes it isn't. The amp is only 3 years old so that's what I would expect. I also thought you'd be able to self diagnose this stuff tho. Give me a while to get my act together and try to check out your suggestions.
Clint 55
OH THE DOUBLE THICK GLAZE!
Clint 55
OH THE DOUBLE THICK GLAZE!
Yes, the amp still powers on.
JMP/HBE
Well-known member
jj tubes are the worst. You may luck out and just need EL-84's after all.
See if you can snipe some off ebay.
JMP/HBE
Well-known member
https://www.ebay.com/itm/1842067159...7VzPJ5FMWeyVtlQuJiUlY85zZ/yU|tkp:BFBMvoi0t9ph
Id still get the amp looked at.
Id still get the amp looked at.
I can tell you right now that the tube on the left is dead. It has gone gassy and caused the getter to go white. The getter is usually a Barium based powered material that is flashed ( induction heated really quickly ) and it flashes up and onto the glass envelope as a silvery, mirror-like finish. This Barium reacts with oxygen/atmosphere when it comes into contact with it and turns white, indicating that the tube has lost its vacuum. When a tube loses its vacuum, it will burn up just like a lightbulb that loses its vacuum does; a very quick light show.
Now why it lost its vacuum is up for debate, but looking at the other tube, they have lived a hard life. I believe they were biased too hot ( as is common with EL84 amp these days ) and this caused a premature loss of life for that tube. You will need to buy another set of tubes and I suggest biasing them a little cooler.
I don't understand the hate for JJ, they are one of the better options these days and they literally supply 33.33% of the tubes in the world, if not more.
Tubes that are biased too hot will have a short life and one way to tell how hot they are biased is to look at the printing on the glass. If it was once red and has turned white or brown over time, it is literally because it is burning. If it is so hot that it is burning, it is biased too hot. That simple.
These days vendors ABUSE the living heck out of EL84's and I'm not sure why? They tend to put 350+ volts on them ( they are designed to run at 250 volts with a maximum of 300 volts on the plate ) and then proceed to bias them way too hot. They sound great for a little while until they are cooked and then they die a horrible death.
I think it is because of copy-and-paste designs. While the circuit is different, they use the same practices that were being done 50+ years ago and disregard the modern voltages and intention of making an amp. They design an amp that is destined to burn up more or less.
Now why it lost its vacuum is up for debate, but looking at the other tube, they have lived a hard life. I believe they were biased too hot ( as is common with EL84 amp these days ) and this caused a premature loss of life for that tube. You will need to buy another set of tubes and I suggest biasing them a little cooler.
I don't understand the hate for JJ, they are one of the better options these days and they literally supply 33.33% of the tubes in the world, if not more.
Tubes that are biased too hot will have a short life and one way to tell how hot they are biased is to look at the printing on the glass. If it was once red and has turned white or brown over time, it is literally because it is burning. If it is so hot that it is burning, it is biased too hot. That simple.
These days vendors ABUSE the living heck out of EL84's and I'm not sure why? They tend to put 350+ volts on them ( they are designed to run at 250 volts with a maximum of 300 volts on the plate ) and then proceed to bias them way too hot. They sound great for a little while until they are cooked and then they die a horrible death.
I think it is because of copy-and-paste designs. While the circuit is different, they use the same practices that were being done 50+ years ago and disregard the modern voltages and intention of making an amp. They design an amp that is destined to burn up more or less.
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JMP/HBE
Well-known member
I don't "hate" anything including jj electronics. I just don't like things that are sh*tty and jj tubes fit that narrative.
Rather than fix their QC issues they just flood the market with more crappy tubes hoping some good ones get thru but they just create more crappy tubes.
Rather than fix their QC issues they just flood the market with more crappy tubes hoping some good ones get thru but they just create more crappy tubes.
Clint 55
OH THE DOUBLE THICK GLAZE!
Thx
