VH4 picking up radio !!

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peter ,
my VH4 picks up the radio at high volumes .
i noticed this when i first got it , then the poweramp tubes blew shortly after and i thought that maybe it was a bad tube causing this .
new poweramp tubes , but it still does it .

also , since changing the poweramp tubes channel 4 has developed a loud "gain hum" , although i only set the gain on this channel at around 8 o'clock .

any ideas ? :confused:
 
Have you tried a different cable. Usually picking up radio is caused by cables from my experience.

I have no idea about the hum :no:
 
for the radio-receiving thing you should try different guitars/pickups and also cables!


EDIT: too late :aww:
 
slate":2n0mvan4 said:
peter ,
my VH4 picks up the radio at high volumes .
i noticed this when i first got it , then the poweramp tubes blew shortly after and i thought that maybe it was a bad tube causing this .
new poweramp tubes , but it still does it .

also , since changing the poweramp tubes channel 4 has developed a loud "gain hum" , although i only set the gain on this channel at around 8 o'clock .

any ideas ? :confused:
Click to expand...

I don't really have a good suggestion concerning the radio receiver issue, but in past I have had similar problems with wah pedals and Russian radio broadcasts :lol: :LOL: . I got rid of all of those problems when I isolated my gear and eliminated the ground loops from my entire rig (one or two heads + 10 units of FX-garbage).

About the hum issue... I believe the power amp tube short also killed the hum trimmer inside the amp. I had a similar experience in the past (viewtopic.php?f=14&t=24060&p=288134&hilit=hum+trimmer#p288134). Easy and cheap fix, but PLEASE if you do not know what you are doing let someone qualified to do it in order to avoid any hazards either to your amp or especially to you.

However, it is possible that the humm trimmer is not neccessarily dysfunctional. To find out that:
1. Remove the head from the head shell.
2. Turn the head upside down laying on something stable from its output transformers (beware not to break the power tubes!).
3. Connect the speaker cable!!
4. Power up.
5. Select Ch4 on normal playing volume and gain.
6. Locate the hum trimmer. (Similar to the bias trimmer, but on the "other end" of the board).
7. Adjust the trimmer and listen. The humm should decay at more or less center position and increase again when adjusted too far. If the trimmer act "weirdly" (such as crackling or scraching noises) it is very likely gone sour and needs to be changed.
8. Buy a new hum trimmer and either change it by yourself, or even better, get someone qualified to do it.
9. Keep on rocking!
 
interesting .... could it be a preamp tube ?
diezel UK just replaced the power tubes - i would have hoped that they would have picked up on this noise also and adjusted/replaced the trimmer .
:gethim:
 
I had an amp fall, and then, it started picking up radio. I re-seated all of the tubes and it went away. Make sure your tubes, power tubes are all seated in good, might take care of the hum, or else, get a good power filter.
 
on further inspection , its actually humming on ALL the channels - its gets progressively louder from channels 1 to 4 .

somethings also gone microphonic - if you tap the head with your fingers a loud metallic clanking noise comes through the speakers .... :no:


it didnt do any of this before the original power tubes blew :confused:
 
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