Sudden redplating problem

jimmyride · Post by **jimmyride** » Tue Nov 20, 2012 4:25 am

Hi there!

I've been enjoying my 12xxx couple of months with no problems and at the beginning of our last rehearsal the HT fuse blew. I changed the fuse and fired up the amp and noticed V4 go crazy. I turned off the amp, changed the tube and turned it on again. All was ok so I started playing. It was all good for like half a minute. Then the V4 started to glow again and the fuse blew once again. I need to solve this problem this week to get ready for the next rehearsal. Any idea where to look? The tubes are NOS Teslas. I plan to order a set of new set of tubes for this kind of testing. The first redplating happened with no input and the volume at zero which is not a good sign as I read it somewhere here.

neikeel · Post by **neikeel** » Tue Nov 20, 2012 6:03 am

You should check the screen resistor on that socket. Then if that is ok swap the valves around to see if it follows the valve or the socket, but check the resistor first.

demonufo · Post by **demonufo** » Tue Nov 20, 2012 6:30 am

+1.

Once you're certain that is good, and you're doubly sure about the tubes themselves, then check bias supply to that socket, and the condition of the 220K bias splitter for that tube...followed by the coupling capacitor - which if it's passing DC, could potentially cause this.

jimmyride · Post by **jimmyride** » Tue Nov 20, 2012 9:17 am

Will do. Thanks guys!

axeman · Post by **axeman** » Tue Nov 20, 2012 4:25 pm

Also, how old are the bias cap's? are hey new. Don't use a CC resistor in that area especially above the diode that's next to the bias cap's

jimmyride · Post by **jimmyride** » Fri Nov 23, 2012 5:48 pm

I got finally my hands on some fuses so I was able to solve the problem. It was bad tube. Not V7 but her neighbour which was taking V7 with her. I'm glad it was so easy. But I almost ran of my strong Teslas... this is not the only one gone bad in this amp. I don't even dime it often. Which is probably the reason - she got simply bored.

Which reminds me... in English - is the tube "she" or "it"? In Czech we use "she" but it looks a bit odd so I thought I'd ask. Anyway... Thanks again for your help guys.

demonufo · Post by **demonufo** » Fri Nov 23, 2012 6:03 pm

In English, we don't really refer to anything as 'she' other than females (of any species). Although, we maybe use it as a term of affection when applied to say, a particularly nice guitar, motorbike, car, amp... something that's special to us.

jimmyride · Post by **jimmyride** » Fri Nov 23, 2012 6:18 pm

Yeah well... aren't the tubes beautiful? Especially NOS EL34s.

demonufo · Post by **demonufo** » Fri Nov 23, 2012 6:54 pm

Indeed. But they look more male than female I guess...

jimmyride · Post by **jimmyride** » Sat Nov 24, 2012 3:59 am

demonufo wrote:Indeed. But they look more male than female I guess...

Oh yeah and plugging them in and playing them is almost an act of love then.

I never thought of it this way. No wonder some people call guitarists the biggest masturbators.

EDIT: Oh and this more than anything explains why the digital amp modeling is all just fake.

demonufo · Post by **demonufo** » Sat Nov 24, 2012 7:47 am

jimmyride wrote:
EDIT: Oh and this more than anything explains why the digital amp modeling is all just fake.

The guitarist's equivalent of a "fleshlight"...

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