Blew a tube, (5U4G) in the 10 watt mode

[Zakkmylde]

Hey guys, i was playing 10 watt mode cranked cause other settings are to loud and im trying desparetly tyring to get tube saturation tone . Playin at 10 watt mode in band practice is loud enough. Anyhow i was playing around at home on 10 watt and having it cranked for hour or so and the first tubes went on me, awfull noises and smell of burnt....i stopped right away and ran and seen tube changing colour and i knew that first tube, (5U4G) in power section gone and broke inside?

Does that mean i cant push 10 watt mode to max for long periods? Or should i look to use 45watt and drop volume down? Or maybe a better tube to use?

Actually not even sure what that tube does as i dont think its a power tube?

 

[screamingdaisy]

The 5U4 is a rectifier tube. It's part of the circuit that converts the wall current from AC to DC.

In guitar amps tube rectifiers are generally less efficient than diode rectifiers. The idea is that as you push the amp harder a tube rectifier fails to produce power quick enough and induces sag, compression and a unique set of harmonics into the circuit.

Putting a lot of demand on a rectifier tube can cause it to fail. Current production rectifier tubes aren't anywhere near the quality that they used to be, so if you're going to push it a lot I'd suggest buying a good NOS one.

That said, I'm kind of surprised that 10w was enough to cause it to fail. So far as I know that tube is good for amps up to 50w.

 

[Zakkmylde]

Oh thank s a lot. I guess there is no way to run amp without that tube to make sure amp is fine? I'll just get a new one and hope its not damaged. I took tube out and turned amp on and hum was crazy loud. Just did it for a sec to test. Amp is month old so hopefully "long and mcquade" music store will replace it

Is there any way to run amp that bypasses this tube to see if amp is ok?

Also thanks a lot screamingdaisy for your replies as I'm new to this amp and any questions I've had you have responded and helped a lot.

 

[screamingdaisy]

If you switch all the channels up to 90w mode the amp should function normally without the rectifier tube... although I could be wrong since I've never tried it myself.

 

[Zakkmylde]

Ok. Will try....

 

[Zakkmylde]

That blew the fuse I believe because power now won't go on at all..... No lights on power or standby.

 

[Boognoob]

Can you not replace the fuse, and switch to diode rectification til you get a replacement tube?

 

[KH Guitar Freak]

If you switch to 90W Simulclass, it automatically reverts to diode rectification only. If you switch to 45W setting, make sure to have the diode rectification selected on the back panel of the amp for each channel. 10W mode defaults straight to tube/valve rectification, so unless you have replaced the worn out 5U4GB valve, don't switch to the 10W setting at all...

 

[Zakkmylde]

Thats when fuse blew, it was on 90 watt mode. I had removed the tube and powered up, waited and clicked on standby and immediately amp shut down. Fuse gone. I'm just gonna buy new tube and hope for the best. Sucks cause now I have to confidence in cranking 10 watt mode

 

[jmontgomery]

I'm thinking replacing the $2 fuse and the $20 tube may be a bit cheaper than buying a new amp. I'd replace the recitifier tube with a NOS one myself.

 

[Zakkmylde]

Well as it stands I replaced new rec tube and fuse. As soon as I power up few seconds later amp shuts down and blows a fuse. So far my boogie experience has been horrible as first one I got 2 months ago I bought used at music store and foot switch was fried, so I opted to buy new and now this amp is also a lemon. Looks like boogie days are over, back to my Marshall Dsl or 5150 The MarkV seemed to be the amp to make me never buy another amp again, bummer.

 

[Zakkmylde]

All good. Power tubes must of had a short. I swapped all power tubes and amp doesn't blow fuses anymore.

 

[jmontgomery]

I'm glad to see you worked it out.

 

[screamingdaisy]

Most tube amp problems are tube related. I keep a full set of spares and fuses just for that reason.

 

[Zakkmylde]

So happy for that. This is first amp that I've had that does this as a fail safe. At least I don't ever recall same issue with my DSL or 5150......I could be wrong. I also just learned how to test for that bad tube by placing them in one at a time and when fuse blows that's the bad tube, kinda cool.

I called mesa about it and they said that using other brand tubes voids warranty fue to their tubes being in such a narrow bias range. So now concerned I can't play around and experiment different tubes like SED winged c or whatever. I don't know which ones are comparable or which ones are in similar range. Right now I'm trying JJ KT77's, I've heard others using them so hope hose are ok.

 

[Chester]

So happy for that. This is first amp that I've had that does this as a fail safe. At least I don't ever recall same issue with my DSL or 5150......I could be wrong. I also just learned how to test for that bad tube by placing them in one at a time and when fuse blows that's the bad tube, kinda cool.

I called mesa about it and they said that using other brand tubes voids warranty fue to their tubes being in such a narrow bias range. So now concerned I can't play around and experiment different tubes like SED winged c or whatever. I don't know which ones are comparable or which ones are in similar range. Right now I'm trying JJ KT77's, I've heard others using them so hope hose are ok.

Not an issue if you buy from a reputable dealer who will test and match tubes to mesa's bias requirements. Call them

I have also used Groove Tubes in my MKV which are great. They are apparently the only non Mesa tube that does not void warranty if you install any matched set rated between 4 - 7 on the GT scale. My current set of EL34's are coded 6 White, and sound excellent

 

[Zakkmylde]

Hi guys, check out this link and tell me what you think. If true you could save a lot of money changing phase inverter tube for different tones vs power tubes

http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf