Strange thing happened while playing VH4

O731

New member
I have a Diezel VH4 that I bought used from reverb, and i'm currently using TAD 12AX7's and JJ KT77's. I was playing on channel 4 just now, and there was like 2-3 pops that came out of nowhere, and my volume dropped quite noticeably. I was able to just turn the master volume up to get the volume back to where it was, but i'm concerned there is something more going on.

Has anyone had any similar experiences happen to them?
 
It's most likely a tube. You may have lost a power tube. Also have had this happen with preamp tubes, where they just go half volume.
 
CrazyNutz":2iy5xo64 said:
It's most likely a tube. You may have lost a power tube. Also have had this happen with preamp tubes, where they just go half volume.


Hmm...Thank you. I looked inside and all power tubes were still glowing. Is it still possible that I lost a power tube?
 
O731":1u8qubt2 said:
CrazyNutz":1u8qubt2 said:
It's most likely a tube. You may have lost a power tube. Also have had this happen with preamp tubes, where they just go half volume.


Hmm...Thank you. I looked inside and all power tubes were still glowing. Is it still possible that I lost a power tube?

Glowing just means the heater is working. Most of the time when they go out, they still glow.
 
There are tube LED's on the back that indicate if a power tube has gone:

vh-4_hi_12.jpg


If they are lit up you need new power tubes.
 
webrthomson":2zics7pk said:
There are tube LED's on the back that indicate if a power tube has gone:

vh-4_hi_12.jpg


If they are lit up you need new power tubes.

Oh wow, I didn't even notice the tube fault light. That is wicked, thanks!

Yup, power tube 2 is out :(
 
Any time you get a used amp, I always recommend going with new tubes - and if you've already experienced the rice krispies snap, crackle and pop, get some new glass in there. Won't hurt to get a couple slow-blow fuses too. Easy enough to find at any electronics shop that know their business.

Bias EL34/KT77 to about 32mA outside pair/inside pair, new fuse, and I'd also consider fresh preamps throughout - high grade Chinese are fine, but you can go spendy and try on a Genalex ECC83 in V1 to govern the stack throughout, and an LPS in the PI. But otherwise, good quality Chinese/Ruby 12AX7s throughout the entire V stage is fine - loop included.

If you do this, you'll have some back up preamp bottles "just in case".
2 cents, hope you love the amp!! It's a classic.
Unkle Mo :thumbsup:
 
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