VH4s ch 3 and 4 noise

  • Thread starter Thread starter diezel&gas
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diezel&gas

diezel&gas

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hello!!

a friend of mine who's got the VH4s head has referred to me he's having some noise from ch 3 and 4.

not knowing the cause he replaced a fuse ( the 1st one from the main input power - that was blown ) and the 4 output tubes but the problem kept staying in.

i told him to check as reported on the tech corner http://diezel.typo3.inpublica.de/tech-corner.3.0.html


VH4:

V1 Used by all channels

V2 Used by channel 4

V3 Used by channel 2/3/4

V4 Used by all channels


what else could-should he check?

thank you!!
 
Turn the hum trimmer a bit to the left or right, if it goes away: replace it.
 
ok so it could be the trimmer?
is it easy to peplace ( like a midi chip ) or it is necessary a soldering job?
thanx! ;)
 
& to check the preamp tubes?

i can't find the guide to check them...

i remember you have to lightly touch them with a pencil....
 
Just swap or change them around.
Tipping them with a pecil just indicates if they are microphonic, which doesn't equal hum.
 
Where is the hum trimmer located in the VH4? I am having some noise (at idle) on channel 3 and 4 as well. But, it may be my guitar or instrument cable.
 
(white) Noise or Hum?

amp flipped, pots facing you:
left bias, right hum - trimmers

edit:
let me explain: the hum trimmer needs "attention" after a power tube change
and esp. after one or more power tubes died.
 
duesentrieb":2bg99lrd said:
(white) Noise or Hum?

amp flipped, pots facing you:
left bias, right hum - trimmers

edit:
let me explain: the hum trimmer needs "attention" after a power tube change
and esp. after one or more power tubes died.
Click to expand...

It sounds almost like RF interference mixed with a little hum and a little white noise. When I turn the guitar volume down, some of it goes away (which tells me SOME of the noise is either from the instrument cable or my guitar). I'll check the trimmer at some point and see what happens.
 
duesentrieb":2g52c6of said:
(white) Noise or Hum?

amp flipped, pots facing you:
left bias, right hum - trimmers

edit:
let me explain: the hum trimmer needs "attention" after a power tube change
and esp. after one or more power tubes died.
Click to expand...

is it required an adjustemnt or a replacement?
 
I'm pretty sure it's the guitar. I was picking up a radio station earlier today. I unplugged the instrument cable from the amp and it went away, even with the master cranked. My guitar isn't grounded, could this be it? I don't think I ever got noise on my previous amp, though. I'd also rather not ground my guitar as I'd have to drill a hole in the body cavity...

EDIT:

I'm getting noise with my other two guitar as well, which are grounded... and not 30 years old like my Les Paul. So, it's not a guitar issue. It's not a cable issue, either as I tried a bunch of different cables that never gave me noise with my previous amp. Does the VH4 cut the signal when there is no cable plugged in to its input? Because I can't figure out why the noise would stop without a cable plugged in...

Channel 3 and 4:

All EQ at noon, master at 9:00: No guitar plugged in = no noise, just idle hiss.

Guitar plugged in with guitar's volume off = RF interference and picking up radio stations.

If I just touch the guitar's strings (volume still off) radio gets much louder, so I'm acting like an antenna. If I roll the guitar's volume on (guitar not near the amp) and touch the strings to keep them from vibrating, on channel 4, I get instant feedback and squeal.

So, microphonic preamp tube?

I tried the tap-test and nothing. None of the tubes (power or pre) pinged or rang out when tapped. However, V1 amplifies vibration in channel 3 and V1/V2 in channel 4, but I just assume this is due to the higher gain in those channels?

V1 is Edicron (Ei) ECC83A
V2 is Ruby 12AX7A
V3 is TAD 12AX7A-C Selected
V5-6 are unlabeled (probably Chinese n'th Generation)
 
Yes, every Diezel cuts the signal (to ground) when no cable is plugged to the input.

I'd replace V1, Mike. EI are (often) notorious for noise . . . . if you need a bright tube, get another chinese or a Telefunken ECC83.
 
diezel&gas":osj2rhe7 said:
duesentrieb":osj2rhe7 said:
(white) Noise or Hum?

amp flipped, pots facing you:
left bias, right hum - trimmers

edit:
let me explain: the hum trimmer needs "attention" after a power tube change
and esp. after one or more power tubes died.
Click to expand...

is it required an adjustemnt or a replacement?
Click to expand...
First try if the problem goes away by turning it a bit. If not: tubes, if yes: replace.
 
The amp has two phase inverters (of course, it is stereo).

Focus on V1 - V4.

What about the trimmer? Did you check it?
 
not yet

it's not mine.

i'm referring to the owner ;)

tomorrow's going to check :rock:

thanx again
 
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