My Mark IV just died on me:(

[Paw]

I bought the amp new about 2 years ago. Occasionally it's been acting a bit strange. Some times it would make a noise which resembles the sound when you turn a scratchy pot, without touching anything. And some times the amp would operate like it should. On some occasions, when the scratchy noise appeared, the guitar would sound weak and lose all sustain. When this was the case, I had to strike a really loud chord or make some kind of loud, trebly sound with the guitar, and suddenly everything would "pop" back to normal, loud and clear. Weird!

Today, I wanted to try out a guitar that I had just set up. The amp was on the tweed setting in standby mode. I wanted to test the guitar with full power, because I prefer the sound over tweed. So I turned off the amp, waited about 10 seconds, and flipped it to full power. It started up for a split second, before it just died: The blue light stopped glowing and the sound from the fan went out. There were no kind of alarming noises or anything, it sounded just like when I turn it off after I've been playing. No bad smells either. Now it won't start...

The amp has rarely been used on higher volume levels due to my neighbors. I usually play at "room level" volume. The amp is only used from time to time due to my studies away from home, and has only been used with the original Mesa tubes that came with it. I've always been using the amp with equal impedance and with the right voltage level (230v, same as amp).

Have anyone experienced anything like this? I'm gonna check if I it's still under warranty

Any help appreciated.

 

[Boogiebabies]

You need new power tubes and a new mains fuse to start. Tone problems could be the preamp tubes.

 

[Paw]

You need new power tubes and a new mains fuse to start. Tone problems could be the preamp tubes.

But why would the fuse blow? Thanks very much for your post, but how can you tell nothing's wrong with the hardware (I hope it's not)?

Looks like I have to buy a full set of preamp and power tubes then, and a fuse. Any suggestions for a good set? I mainly play metal but also rock.

 

[Boogiebabies]

To protect the output transformer a shorted power tube will blow the fuse.

 

[Paw]

To protect the output transformer a shorted power tube will blow the fuse.

So this was probably due to a bad tube?

Very much appreciated Boogiebabies!

 

[Bro KV]

You need new power tubes and a new mains fuse to start. Tone problems could be the preamp tubes.

But why would the fuse blow? Thanks very much for your post, but how can you tell nothing's wrong with the hardware (I hope it's not)?

Looks like I have to buy a full set of preamp and power tubes then, and a fuse. Any suggestions for a good set? I mainly play metal but also rock.

I just put this set in my Mark IV and love it to death

Mesa MK IV 6L6/KT77 High Gain Option
Price: 140.75
Description: This kit uses a pair of JJ 6L6GC's for depth and punch and a pair of JJ KT77's for chunk and crunch. For the front end 5 JJ ECC83S's, 4 hand picked high gain tubes for V1, V2, V3 and V4, and a balanced ECC83S for V5. For players after the Petrucci or Satrani tone.

https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=6&sub_category_id=60

 

[Boogiebabies]

To protect the output transformer a shorted power tube will blow the fuse.

So this was probably due to a bad tube?

Very much appreciated Boogiebabies!

Your scratchy issue is most likely a bad V1 preamp tube and your blown fuse is power tubes.
You may not have to change all of your preamp tubes, but two years on power tubes is about
80% the right time to change them if the amp is used daily. Bad Power tubes can actually work just fine in tweed mode
and you would never know until you switched to full power. If you have used the amp or power tubes for less than 300
hours and you are in a financial pinch, you could replace the fuse and start the amp up and leave it in tweed
to make sure it works. It may give you another few weeks to save up for power tubes and a new preamp tube.
Sometimes these amps will blow a fuse simply switching from tweed to full power even with good power tubes, but if
you have around 500 hours on them it will be time to change them for better reliability in the future.

 

[Paw]

To protect the output transformer a shorted power tube will blow the fuse.

So this was probably due to a bad tube?

Very much appreciated Boogiebabies!

Your scratchy issue is most likely a bad V1 preamp tube and your blown fuse is power tubes.
You may not have to change all of your preamp tubes, but two years on power tubes is about
80% the right time to change them if the amp is used daily. Bad Power tubes can actually work just fine in tweed mode
and you would never know until you switched to full power. If you have used the amp or power tubes for less than 300
hours and you are in a financial pinch, you could replace the fuse and start the amp up and leave it in tweed
to make sure it works. It may give you another few weeks to save up for power tubes and a new preamp tube.
Sometimes these amps will blow a fuse simply switching from tweed to full power even with good power tubes, but if
you have around 500 hours on them it will be time to change them for better reliability in the future.

The tubes have nowhere near 500 hours. Maybe a maximum of 150 hours on low volume use (lots of these hours in standby mode). What I now wonder is if I still can use the same power tubes in my amp, or if it's some kind of risk due to the possibility of a bad power tube? If I understood your message right, there may be nothing wrong with the power tube(s), just that the fuse may blow when the amp switches between tweed and full power.

I've been thinking of getting some new tubes for the amp for some time, and I'm gonna, but not right now. So, if I go out and buy a new fuse, install it, and fire up the amp with the same tubes, will I risk some damage to the components in the amp due to a bad tube in one of the sockets?

Thanks guys!

BTW: Thanks for your suggestion Bro KV. I'm gonna look into it

 

[Boogiebabies]

It will blow the fuse again for sure if it's a bad power tube. Just keep your eyes on them for a while.
If it runs fine in tweed keep looking at the power tubes for a while to make sure the plates don't
start glowing red. The plates are the flat gray colored objects in the tube. Gray=Normal, Red=Over Heating.
Don't confuse the orange glow in the middle. Those are the heater filaments.
If you see one turning red while playing, turn the amp quickly to standby to save the fuse and go buy new power tubes.

 

[Paw]

It will blow the fuse again for sure if it's a bad power tube. Just keep your eyes on them for a while.
If it runs fine in tweed keep looking at the power tubes for a while to make sure the plates don't
start glowing red. The plates are the flat gray colored objects in the tube. Gray=Normal, Red=Over Heating.
Don't confuse the orange glow in the middle. Those are the heater filaments.
If you see one turning red while playing, turn the amp quickly to standby to save the fuse and go buy new power tubes.

Went to the store and bought some fuses, put one in the amp and fired it up. No problems. I did briefly experience sound loss, but that is possibly due to a bad preamp tube like you pointed out to me Boogiebabies One thing I noticed was that the two tubes to the right (from behind the amp) glowed lots of blue, while the one all to the left almost had no blue glow and the one next to it was somewhere in between. Does this mean that the ones with less blue glow are bad ones?

Also, after checking out the manual, it says that I can tap the tubes to hear if it's a bad one. Is this while the amp is on, not on standby? What will I hear if it's a bad one?

Thanks once again. You guys are the best.

BTW: No tubes turned red.

 

[Boogiebabies]

The blue glow is leftover cobalt. Some glow brighter than others, but it may mean that the tube that is glowing the least is either
made with less impurities or it's on it's way out. Bad power tubes can also cause your signal to drop out so it's a good time to replace them.
They will get you by for a little while but I would replace them ASAP.

If you tap on a microphonic preamp tube you will hear the tapping loudly through the amp. Sometimes it will cause the tube to sputter, crackle
or make a "Ting" sound.

 

[Bro KV]

I also have been getting a lot people telling me about Winged C tubes. I am picking up a set of quad set of 6L6s just to try something else.

 

[topcat0399]

I bought the amp new about 2 years ago. .............

im still scratching my 'ead over this part but.....glad you are having better luck now.



cheers

 

[Paw]

I also have been getting a lot people telling me about Winged C tubes. I am picking up a set of quad set of 6L6s just to try something else.

Yeah, me too!

Who makes them (what company)? Where can I get them? I've been thinking of buying two different sets (JJ's and another) just to get some tube experience, and it's always handy to have a few backup tubes

 

[Bro KV]

I also have been getting a lot people telling me about Winged C tubes. I am picking up a set of quad set of 6L6s just to try something else.

Yeah, me too!

Who makes them (what company)? Where can I get them? I've been thinking of buying two different sets (JJ's and another) just to get some tube experience, and it's always handy to have a few backup tubes

I just ordered mine from here

http://www.tubesandmore.com/

Winged C Made in St. Petersburg, Russia factory. Same factory and specifications as the Svetlana branded tubes produced prior to 2003.