Changing V1 preamp tube is risky

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guitarsawicki
Mark II
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Changing V1 preamp tube is risky

Post by guitarsawicki » Tue Jul 02, 2019 4:55 am

I changed the V1 preamp tube (put that huge cover back also) and it was not easy. After that only hum could be heard from the speaker. I removed the V1 tube and it looked fine. I put it back (but not that huge cover) and still no sound. I removed the chassis and it is ridiculous how difficult that was. Then I saw that V1 glass was broken and that white stuff was on the top of the tube. Then I changed V1 tube and everything worked again. I must make hole to wood underneath the front grill so that V1 changing would be easier.
Mark V 90W 2013 head
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Wayno
Mark III
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Re: Changing V1 preamp tube is risky

Post by Wayno » Wed Jul 03, 2019 2:06 pm

Very tricky job to change v1 without removing chassis. Even in the combo it's difficult.
Her highness the Veenus
(Mark V/V4 & V7 12AT7 Combo)

2 x 12 Vertical Cab
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Bankim
Mark II
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Re: Changing V1 preamp tube is risky

Post by Bankim » Thu Jul 04, 2019 9:34 pm

I have not removed the chasis ever in my 5+ yrs of owning it.. here is how you do it.. for amp head only.

Step 1 : Turn the amp upside down and let it sit such that the tube sockets point up.

Step 2 : Remove all power tubes n rectifier tube

Step 3 : Reach in with hands and slowly pull out V1. Remember the pin spacing when you take out the v1 tube.

Step 4 : Put in the replacement tube with the correct pin spacing as when you took it out in step 3.

I remember seeing a youtube video on this. Let me put in a link to it later ..
Mesa Mark V Head
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