Mesa died! Fuse?

[imjustadrummer]

Playing at high volume with heavy attenuation the other night, things started sounding fizzy and then just cut out completely... no sound. Nothing in the effects loop. The jewel power light even went out!?!?

The fuse looks ratty but not completely separated...
power tubes look alright...

Is this likely just the fuse or something else/worse?

[Blue Strat]

You have to check the fuse with a meter to find out. Either that or replace it with another one and see what happens.

No point in guessing what else might have happened without knowing the status of the fuse.

[mike80]

Check it with a different fuse, or check for continuity on the fuse. Sometimes the element in the fuse won't break, but the fuse will still be bad.

If the fuse is replaced with a known good one and it still won't work, it's likely the power tranny.

[RussB]

If the fuse is replaced with a known good one and it still won't work, it's likely the power tranny.


I know you're trying to help, but that is some of the worst advice I'm yet to read on the 'net.

A power transformer seldom expires. That's why amps use fuses, they protect the rest of the circuitry. Fuses blow because there is a short circuit in the amp...

The more likely scenario is a power tube shorted, due to being pushed hard through the attenuator. Mesa'a come with cheap russian and/or chinese tubes.

And ALWAYS use the correct fuse! Never go up in amperage rating!!

[mike80]

Well, if the fuse is replaced or good, and the amp still won't power up, what's next in line...the power tranny. ;)

Agreed, most likely a shorted power tube that took out the fuse. My post should have read "If it still won't power up." Even if they rarely go bad, sometimes they do. Probably not the case here though.

Is that better?

The statement about fizzy sound at first does lead me to believe it's just a bad power tube.

[Blue Strat]

Well, if the fuse is replaced or good, and the amp still won't power up, what's next in line...the power tranny. ;)




But more likely than the PT are power tubes, rectifier diodes or tube, power supply capacitors, etc.

The power transformer is the least likely scenario.

[SatelliteAmps]

Power transformer is most likely the least likely culprit. And it is bad advice. There is nothing to indicate a bad transformer and it is not necessarily the next in line from the fuse. Fuses pop when the current draw becomes more than the fuse will allow. Not because a transformer is blown. When something shorts in the amp, it will try to draw more current to compensate, which will cause the power transformer to try to draw more current which will pop the fuse WAY before it will kill the power transformer.

A ratty fuse is a popped fuse. Probably a slow blow that now has a bunch of little dots on it because it popped. They are cheap. Use the right replacement. Get a few to have on hand in the future.

Chances are, bad power tube, rectifier, or caps. It's really easy to find out. Take out all the tubes. Put in a new fuse. Turn the amp on and see if it lights up. If it does, then chances are you have a bad tube(s). If not, then take it to a tech to have them trace it down.

[guitarsnguns04]

+1 tube problem...power or rectifier...

[imjustadrummer]

yes... little dots all over it like spilled mercury...

My local music store doesn't carry the 2.5A fuse the Mark requires...
would an auto-parts store have one... anywhere else?

[TopBooster]

Radio Shack should have them... Make sure you get the slow blow type.

[imjustadrummer]

Mike,
I've got a pair of RI Tung-Sol 5881s lying around... how would these be in the Mesa Mark IIC+ 60 watt?

[Blue Strat]

Radio Shack, Lowes, Home Depot...

[teleamp]

Well, if the fuse is replaced or good, and the amp still won't power up, what's next in line...the power tranny. ;).....

No, Mesa's have a varistor that can go bad.