Blown Fuse.... again

[Mark V]

So yesterday at band practice, I was shredding some leads, while suddenly my sound was gone...
I looked at the amp, and hey... all lights were out.. I checked the fuse and discovered it was was blown...again.
Last time it happened was about two months ago...
At the time I took it to the shop where I bought it, and they 'checked it out', but they said all tubes were fine, so it probably was a power issue at the rehearsal room....

Fair enough...

However! Since then, I have a Furman Power Conditioner where the Mark V is attached to, as well as my Relay G90 wireless system, Korg rack tuner, and G-Major 2.
They were still powered on when the fuse blow on my Mark V... So I doubt it was a power issue again yesterday.

I replaced the fuse and could continue to play. I also took a look at the tubes, and they seemed all just fine.

Now why would this happen?

Two things have changed:

I played for a year with just my Mark V combo, no fX.
Also I just carried it around in the slipcover it came with.

since about three months, I have a flight case where the Mark V combo fits in, together with my rack gear.

(The Korg tunerisn't in that picture yet)

Anyway, as you can see the front an back panel can be removed, so the amp itself should have enough cooling from the back.
So it can't be an issue of overheating, because the amp would then just shut down, and not blow a fuse..right?

So the only thing I can think off then, is the G-Major 2...
I'm using the relay switch on the GM-2 to change channels on my Mark V (stereo to 2 mono jack)
I saw some threads about people not advising to use relay switching with the G-major and Mark V because of some issues grounding issues, but I never found any official thread about this.

Anyone else has an idea about why that bloody fuse blew?

thanks!

 

[scoden]

change the rectifier tube asap

 

[Rkorn]

Beware of Furman... most of them are not current elevator (i believe this is how you say it).
Above or below some current they will shut down!
I believe what you have is a current stabilizer, if it drops down of goes higher that what it holds, it will blow the fuse! I have one also and it has happened!
The best ones are to expensive and I don't have the money for them at the moment...

 

[primeholy]

Are you taking the back off the flight case when you jam? If not I'm sure it is retaining a lot of heat, and that could cause problems.

 

[thunda1216]

change the rectifier tube asap

+1. A rectifier tube can have intermittent shorts that will take out the fuse. It will work for a while, then short. Been there, done that, pulled my hair out. If you can find an NOS GE model, you will get better mileage, but less sag than the Shuguang model.

 

[primeholy]

So do you think you have remedied the situation?

 

[Mark V]

Well since I replaced the fuse, the amp works just fine again. (just waiting for the next blown fuse I guess)

Did a gig with it last saturday and no issues.
This friday I have another gig, so we'll see.

But I'm always putting each channel at 90watts, so the recto tube isn't used then...correct?
So would the recto tube really be the issue then....?

I'll be looking for a replacement recto tube anyways and see what that says..

I'll also be saving up for a Mini Amp gizmo to switch channels instead of the relay + jacks on the G-major, maybe there's an issue with that after all..

 

[scoden]

Its either a flaky rectifier or power/pre amp tube..change out any tubes over 6 months old.you are pushing your luck just changing fuse and gigging.you may blow a screen resistor next time and you will then have to get it serviced instead of just tube swap.

 

[EtherealWidow]

Even though you don't have it set to tube rectification a bad rectifier tube can still cause the fuse to blow.