Troubleshooting VH4

I'm trying to troubleshoot a noise issue. It's not that bad of an issue, but I don't know what's causing it. On channel 3 and 4 I'm getting RF Interference (a local radio station) when the guitar's volume knob is off. When I touch the guitar's control knob it gets louder (this happens on three different guitars and I've tried different guitar cables). I put a new preamp tube into V1 and SOME of the background hiss/hum and static went away, but the radio station the amp is picking up is not much more clear.

I swapped V4 and V2: Radio station got quieter on channel 3 and louder on channel 4. Swapped them back.

Swapped V4 and V3: Channel 2, 3 and 4 now pick up radio station and when I switch to channel 4, I get a squeal only when I hit the channel button.

Either I have 4 microphonic preamp tubes or something else is the issue. Well, 3 microphonic since I replaced V1. Would a microphonic preamp tube cause the amp to pick up a radio station like a distortion pedal and wah pedal?

ALSO:

Whenever I turn the amp on something different happens. Sometimes all the channel lights, send 2 light, insert light and mute light blink (store light does not blink). Sometimes nothing lights up, sometimes one of the channel lights go on (whichever I was last using, probably). Is this normal, or do certain patterns of lights indicate a different thing?

Other than the RF Noise, the amp seems to be working fine (although I don't use the MIDI functions, so I can't check that).

Right now, all the lights are blinking. If, while in standby, I hit the mute button, it goes off and all the other lights stop blinking, but stay on. If I flip the standby switch, nothing changes and all the channel lights are still lit. It sounds like channel 1 is coming through, but all the channel lights are on....

If I hit a channel button, that channel will go on and the amp will act like normal.

If I touch the channel buttons for 2, 3 or 4 OR while in those channels press the send 2 or insert buttons, I get the same audible high-pitch metal sound. If the amp is in the mute mode and I press the insert button, I get a loud hum.

So... what's going on here?

So, to recap: Weird flashing lights (sometimes) but doesn't seem to be a problem except for RF Noise.

Lets wait until (our time) tomorrow morning, Peter will reply then.

In the meantime (I'm serious) try another 120V/wall in your room and a different position of the amp inside the room. Under certain weather conditions and with a bad power supply IMO it can happen with many high gainers. I myself never had it with a Diezel though . . .

duesentrieb":3uw2nlfk said:

Lets wait until (our time) tomorrow morning, Peter will reply then.

In the meantime (I'm serious) try another 120V/wall in your room and a different position of the amp inside the room. Under certain weather conditions and with a bad power supply IMO it can happen with many high gainers. I myself never had it with a Diezel though . . .

Click to expand...

That's what I was thinking, too. But, I've been using the same power outlet with my other amp and had no noise issues. But, I'll try it. I'm also going to try replacing all the preamp tubes with new ones.

But, what's with the blinking lights and hum on the channel insert mode while muted?

My on VH4 is in the rehearsal room - and I don't use mute, but I think I remember that it blinks while muted. Can't tell why it is humming though. Others may chime in . . .

duesentrieb":2cacqind said:

My on VH4 is in the rehearsal room - and I don't use mute, but I think I remember that it blinks while muted. Can't tell why it is humming though. Others may chime in . . .

Click to expand...

I think blinking on mute is normal. But, it does something different each time I turn it on. Sometimes every light blinks, sometimes it goes to a channel like normal, sometimes no lights come on...

If the Channel Insert is switched on (nothing in the loops) it hums while in the mute mode. I moved the amp to a different room and plugged into a different power outlet. Noise is still there.

I would first try a different speaker cable.
Then a rif filer, usually built in many surge protectors. If your power picked it up, it's probably all over your house, moving to a different room won't fix it.

The amp cannot recieve radio frequency.
This happens in front of the input on Your guitar or guitar cord.

If the LED´s are flashing when You switch vom standby to run
a high voltage spike causes a reset on the controller chip.
This can be caused by a bad tube or a bad cap on Your
high voltage rectifier.

But first I would send You a new controller chip, so I need the
serial number of the amp.

For the hum with channel insert and mute: I think it will disappear
when an effect unit is in the channel insert loop. I know about that
issue but it makes no sense to use the channel insert without
anything plugged in.

If You hear a "ping" while switching the channels You have a microphonic
preamp tube.

For further help please contact me at peterdiezel (at) diezelamplification (dot) com

Thanks,
Peter

Peter Diezel":1hbdb3fy said:

The amp cannot recieve radio frequency.
This happens in front of the input on Your guitar or guitar cord.

If the LED´s are flashing when You switch vom standby to run
a high voltage spike causes a reset on the controller chip.
This can be caused by a bad tube or a bad cap on Your
high voltage rectifier.

But first I would send You a new controller chip, so I need the
serial number of the amp.

For the hum with channel insert and mute: I think it will disappear
when an effect unit is in the channel insert loop. I know about that
issue but it makes no sense to use the channel insert without
anything plugged in.

If You hear a "ping" while switching the channels You have a microphonic
preamp tube.

For further help please contact me at peterdiezel (at) diezelamplification (dot) com

Thanks,
Peter

Click to expand...

Thanks, Peter. I'll send an email. But, I'll post a response here as well.

I've been using two other amps with the same cords for years without any radio noise. So, I don't know why just now all my guitar cords and my three guitars suddenly started to pick up radio.

LED lights aren't flashing when I switch to run. They flash while still in standby. I turn the amp on, all the lights go on, then off... then they all either start flashing, they all go off, or it goes to one of the channel lights. When I switch to run, the amp works pretty much normally. I was just wondering why something different happens each time.

I put an effect in the channel insert on each channel and the hum is still there while on mute.

I will also replace all the preamp tubes. The amp's serial is 050587.

Thanks,

first step would be solder a cap with 100pF across the input jack
from hot to ground. This should suppress the radio signal if it
appears on the input.

Be sure that the chips on the midi board inside the amp
are tight in the sockets.

Use highgrade 12AX7AC5 HG+ on V1 and V2.

Peter Diezel":6kc5wz5t said:

Thanks,

first step would be solder a cap with 100pF across the input jack
from hot to ground. This should suppress the radio signal if it
appears on the input.

Be sure that the chips on the midi board inside the amp
are tight in the sockets.

Use highgrade 12AX7AC5 HG+ on V1 and V2.

Click to expand...

Will the new cap on the input effect the sound of the amp at all?

I'll look at the MIDI board.

Are those tubes Ruby? And email sent.

Thanks.