VH4 - Weird ring / noise on channels 2,3,4

[aconole]

Hi all, not sure where else to post. I recently purchased a Diezel VH4 and have noticed that on channels 2, 3, and 4 that I get a weird almost feedback like noise. This isn't present on channel 1. No amount of gain / vol adjustment makes it go away. It does change level with these settings (ie: when volume is cut to 1/2, the noise is cut by 1/2). I'm not sure whether there is a setting somewhere I need to look at that I've missed. I have put two other amps on the same circuit to test - neither have this issue. The issue is not present on channel 1 - nice and clean there. I'll try and get a video / audio later this week and update the thread. Any advice on simple things to check out?

 

[Flintstonerocks]

My two cents……Sounds like a one bad preamp tube in sockets 2 thru 4. I would remove the preamp tube covers, power it up, and tap lightly on each tube with a pencil. If you get a really strange noise, that’s your bad tube.

 

[Philhouse]

Sounds like a preamp tube issue. Start with swapping out V3 as it does ch 2/3/4.

 

[FLUXX]

Check out Eurotubes.com, they have replacement JJECC83s Preamp tubes for the VH4.
You can buy one tube, or a whole replacement set.

 

[aconole]

Thanks for the help. I swapped V3 and V2 just to test (based on a technician PDF that I found), and now channels 2, and 3 are sounding great. Looks like I'll need to get at least one tube.

 

[zeen]

Thanks for the help. I swapped V3 and V2 just to test (based on a technician PDF that I found), and now channels 2, and 3 are sounding great. Looks like I'll need to get at least one tube.

I think V2 is used only CH4, so if you swapped V2/V3 I guess you swapped the faulty tube to V2, serving CH4 only...

 

[Ventura]

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