VH4..Went Silent During Playing, 1st Issue In 15 Years

[Pain]

Long time VH4 owner, finally hit a snag and just curious if this issue rings a bell so I focus more in 1 direction. I've fixed amps before in basic ways but sometimes there's a known issue or this smells like this 75% of the time so I'll ask.....

Amp turns on and lights up
All channels can switch
No sound out any channel
Amp was playing on Ch2 then went dead
Cable tested out good
Guitar tested out good
Rear power tube lights on back panel are NOT on, all LEDs are not lite up
All tubes look to be lite up brightly except V3 (slot 4 from the left if looking in) this tube looks diminished in light.

I haven't touched it yet, literally just happened during a recording session. Lucky we went to the Herbert and all is good. I have extra preamp tubes to swap but even there......

What Preamp tubes are Pappa approved these days?

This is a 2010 era VH4 if curious and the only mod was a Poppa approved Ch4 tightness capacitor for fast lead playing, otherwise this has been a flawless amp with not even close to 750 hours on it since it's my Precious. Thanks

 

[Pain]

Issue found and resolved....

Preamp tube 6, slot 7 (slot 2 is capped off) was bad.
I thought the amp was 100% dead but it was just super quiet in my dead room.

But I'm a TAD bit confused (lame joke) on the tubes since I thought Diezel preferred TAD7025bs....

TAD 7025b in all slots except tube 6, ECC83.

Then....
Slot 7 tube is supposedly Ch3 and 4, yet ALL channels were super quiet?

Tubedepot carries TAD 7025 (NOT b), $32 each, not in stock as of 1-26 but it's time so I'll swap them all.

 

[Pain]

Just did an order with Eurotubes, talking with them is the best.

Ecc83s
High Gain Ecc83s to test in V1-V2
New E83cc to test in V1-V2

I'll see what I prefer in my VH4 with recordings of the same riffs and leads, then listen in real time back to back.

Sounds like 12AX7-C is the Diezel fam recommendations, Eurotube doesn't offer Chinese tubes so I went with their tested and approved options above and I'll hear what I think in the end.

 

[Philhouse]

Hey,

The tube layout should be as per:

Tube layouts

VH4:

V1 = input stage for all channels

V2 = channel 4

V3 = channel 2,3,4

V4 = all channels

V5 = mixer and send buffer

V6 = return driver serial and parallel

V7 = phase inverter
Here's a link for the service manual for some more info.
https://www.diezelamplification.com/manuals/service/service-manual_V1-3.pdf

https://www.diezelamplification.com/manuals/en/VH4&VH4S_Manual_05062024.pdf


I'm unsure what the current Diezel preferred tubes list is. It used to be on the website under 'support' documents but I can't seem to find it now.

You should be ok with any good quality 12AX7 for V6 to get the amp going again. V1 and V3 seem to be more particular to higher quality tubes in those slots.

Cheers,
Phil

 

[Techdeth]

Hey,

The tube layout should be as per:

Tube layouts

VH4:

V1 = input stage for all channels

V2 = channel 4

V3 = channel 2,3,4

V4 = all channels

V5 = mixer and send buffer

V6 = return driver serial and parallel

V7 = phase inverter
Here's a link for the service manual for some more info.
https://www.diezelamplification.com/manuals/service/service-manual_V1-3.pdf

https://www.diezelamplification.com/manuals/en/VH4&VH4S_Manual_05062024.pdf


I'm unsure what the current Diezel preferred tubes list is. It used to be on the website under 'support' documents but I can't seem to find it now.

You should be ok with any good quality 12AX7 for V6 to get the amp going again. V1 and V3 seem to be more particular to higher quality tubes in those slots.

Cheers,
Phil

Good info . I need to retune my vh4

 

[Pain]

Thanks, the document I saw online was clearly wrong on the slots. After seeing this I agree that I'll do my tests with V1 and V3 as the swapped tubes.