MKIII issue HELP PLEASE!

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Forsaken_Flesh0213
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MKIII issue HELP PLEASE!

Post by Forsaken_Flesh0213 » Wed Aug 02, 2017 12:50 am

My MKIII keeps popping in and out when I am playing. I have noticed that one of the tubes starts to glow super bright and then fades really quickly. During the fade is when sound from the amp stops. Looking at the back of the amp it is the right middle tube. When it begins to glow bright if I switch the amp to "standby" it fades to its normal glow. I am a bit of a novice to tube amps, so is this tube bad or going bad or is there another issue that is going on? Help please kind Oranglings.

Jondog
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Re: MKIII issue HELP PLEASE!

Post by Jondog » Wed Aug 02, 2017 1:57 am

Sounds like a bad tube. Not familiar with the tube layout of the MKIII. Is it a large tube (power tube) or small (pre-amp tube). Also does it affect both channels?
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Forsaken_Flesh0213
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Re: MKIII issue HELP PLEASE!

Post by Forsaken_Flesh0213 » Wed Aug 02, 2017 11:19 pm

Jondog wrote:
Wed Aug 02, 2017 1:57 am
Sounds like a bad tube. Not familiar with the tube layout of the MKIII. Is it a large tube (power tube) or small (pre-amp tube). Also does it affect both channels?
It affects both channels. I think that there are only 4 large power tubes inside. I do not see smaller ones in there. Also, I did forget to add that it has blown 2 fuses that reside under the power cable during these issues. I have replaced them with exactly what it calls for both times.

Jondog
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Re: MKIII issue HELP PLEASE!

Post by Jondog » Thu Aug 03, 2017 12:00 am

Forsaken_Flesh0213 wrote:
Wed Aug 02, 2017 11:19 pm
Jondog wrote:
Wed Aug 02, 2017 1:57 am
Sounds like a bad tube. Not familiar with the tube layout of the MKIII. Is it a large tube (power tube) or small (pre-amp tube). Also does it affect both channels?
It affects both channels. I think that there are only 4 large power tubes inside. I do not see smaller ones in there. Also, I did forget to add that it has blown 2 fuses that reside under the power cable during these issues. I have replaced them with exactly what it calls for both times.
I'll assume we're talking about the power tubes. The smaller preamp tubes are definitely in there, they have aluminum shields over them. If that mains fuse blows I would not play the amp until you have the problem sorted. It's a bit concerning the HT fuse isn't blowing first (its the one in the circular holder). The mains fuse is in the 'drawer' attached to the power socket. Definitely get it to a tech. You dont want to fry your transformer(s). Hopefully just a bad tube.
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Les Paul Lover
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Re: MKIII issue HELP PLEASE!

Post by Les Paul Lover » Thu Aug 03, 2017 11:26 pm

Sounds like you have a power valve issue, which is why you sound is dropping in/out, and the fuse blowing.

Since the amp needs to be biased when you change power valve, you need to find a tech and bring it in.
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


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