VH4 Channel 4 - super low output

  • Thread starter Thread starter sloafmaster
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sloafmaster

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I recently have had some problems with channel 4 of my VH4 - it cut out during practice (dramatically lower volume, almost silent). I figured it was the preamp tubes since I think one of them is specific to channel 4. I retubed (replaced pre- and poweramp tubes) and rebiased the amp and things seemed to work smoothly again for a couple hours of play time, but now the problem seems to be back.

Has anyone run into similar issues with this amp?
 
Welcome to the forum :thumbsup:

Did you re bend the clamps in scket V2 ?
 
Thank you for the quick reply! I'm afraid I'm not totally sure what you mean by "re bend the clamps", which probably means I did not do it. When I installed the preamp tubes, I basically just pulled the old ones out and pushed the new ones in. If you don't mind, could you give me some more detail on what re-bending the clamps means?

I should add that I've owned this amp for several years and have had zero issues so far. Thanks for designing such a reliable and great sounding piece of hardware!

EDIT: Are you referring to something like this: http://www.el34world.com/charts/fenderservice2.htm (last section) ?
 
I'm pretty sure that's precisely what he means. Make sure they're grabbing those tube pins solid.
 
Just tried bending the socket clamps and re-seating the preamp tube, but it didn't seem have an effect - i tried several times.

I did notice that V2 has a very bright glow that the others don't have:
diezel_v2_glow.jpg


I then tried replacing V2 with another preamp tube from my old set (TAD 12ax7a-c selected) and it seems better (the intense glow seems gone), although Channel 4's output seems a bit lower than channel 3.

EDIT: slyvren: thanks for the reply!
 
My chan 4 is always lower than 3 by a little. I think it has to do with channel 4 being more compressed. Actually, it seems that each channel is a little quieter than the previous. That's one of the reasons there are so many volume knobs. Just set chan 3 lower and crank the master some more!

Glad you got it sorted.
 
Thanks again for the reply!

It's working now, but I'm honestly a little worried about V2, considering the timeline:

  • channel 4 died
    I replaced all the preamps
    (couple hours later) channel 4 dies again
    replaced V2 with one of the old pres
    working for now?
Looking at that, I'm concerned that there's something about the amp that's causing harm to the V2 preamp tube. Am I totally off-base here?
 
It could be a combination problem of a faulty tube and the retainer. The tubes could very well have gone bad because of the pin not making proper connection? That's my guess, but I am far from being an expert like Papa. Maybe he will chime in with some more knowledge.
 
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