Trouble solved with VH4

[Simop]

I'm having some problems with my VH4. 4th channel has started buzzing, humming and hissing way too much. Level of that ruckus is about 1/3 of what comes out from my cab, so it's barely buried beneath my sweet guitar music. I have changed preamp tubes and it doesn't seem to solve the problem. Does anyone have any ideas? I'm going to give it to an amp tech but I'm doing some research beforehand to help him out as much as possible. A good starting point for tech could also save me some money.

There's also this one intresting thing about deep-pot. It starts to feedback when turned to max. This isn't the normal squeling type of feedback but rather a low hum around 100-200Hz. It's amplitude or tone doesn't change no matter where the other knobs are turned. It really doesn't matter since one couldn't possibly use it as much as that, but I'd like to know whether it's normal or not.

 

[Peter Diezel]

Please replace V1 and V2 again.

For the feedback Your impedance may be not
completely matched and/or Your speakers
support the frequency.

Do You need the deep knob at maximum ?

 

[Simop]

Please replace V1 and V2 again.

For the feedback Your impedance may be not
completely matched and/or Your speakers
support the frequency.

Do You need the deep knob at maximum ?

Thanks for a quick reply Peter!

Okay, I'll try replacing them with different tubes. The ones I tested with are crappy ENGL-tubes from my old Screamer and they could be bad as well. V1 & V2 are TAD Highgrade 7025 tubes atm. The first one is the original and second one is from my old Einstein. They should be working ok but you might never know...

About the deep knob: absolutely not! I was only fooling around with my amp and tried what it's capable of. Somewhere around 11:00 is more than enough for my needs. Sometimes there's no need for any. As what comes to my cab it's a Rivera K412T with V30 & G12K-100 wired as stereo (2x8ohms). I've been thinking of wiring it to mono, could this solve my feedback problem? Well it wouldn't hurt to try since I don't have any use for a stereo cab.

 

[Simop]

Nope, no help with changing new tubes. I propably know the reason for my original problem and it's going to get fixed someday soon. Unfortunately I'm not too familiar with these technical terms in english so I can't name the component at fault.

Also one new major problem occurred: it blew my mains fuse when we tried to turn mastervol to 15:00 just for a quick test. Changed it to a new one and turned amp on with master turned down to zero. Stand by seems to work normally (no tube fault leds are lit etc.) and when turned it on lights blink twice, a squeal comes out of cab --> fuse blows again and that familiar smell of burnt components comes out of VH4. Not a good sign...

Btw. are my fuses the right ones? Manual says 4A slow blow and fuses (original, dunno?) say T2A 250V if I remember correctly. Slow 2A anyways. Even if they were underrated I assume they couldn't have possibly caused this?

 

[Peter Diezel]

Hmmm...Finland is 230 volts and the fuse is 2AT / 2 amps slow blow.

When I dealed with EL34/6L6 types 30% of new tubes went
into trash can. So nothing new about broken "new" tubes.

For example: Today I added two Herberts more for Japan
shipment. They want to have EL34B-STR. After the test
managment I had 7 from 12 tubes broken

6550-SED and never look back

 

[Simop]

Blah blah blah... I'm still waiting for my VH4. I gave it to the distributor exactly a month ago to be fixed but nothing seems to happen... Maybe just bad luck and a tight schedual. Hopefully nothing is seriously broken as I'm not the original owner --> no warranty.

This is just... It kind of sucks when one has to borrow some random heads from various people to play gigs. Wish I were rich and had a spare one.

 

[Simop]

All problems solved, hopefully!

There was something wrong with EL34's as they had blown up the hum trimmer. Also my TAD pre's broke something --> a whole lot of stuff had to be repaired and 4x EL34's & 2x ECC83's to be replaced... Costs quite a bit but guess it's worth it to get my VH4 back.

Also Peter, thank you very much from your help! I heard from Björn that you had assisted him personally (via telephone in this case) diagnosing my amp.

 

[Joeytpg]

All problems solved, hopefully!

There was something wrong with EL34's as they had blown up the hum trimmer. Also my TAD pre's broke something --> a whole lot of stuff had to be repaired and 4x EL34's & 2x ECC83's to be replaced... Costs quite a bit but guess it's worth it to get my VH4 back.

Also Peter, thank you very much from your help! I heard from Björn that you had assisted him personally (via telephone in this case) diagnosing my amp.

Good to hear everything's fine again. I had to send my VH4 to Peter and ended up spending a bunch of cash on it (thank god Peter was kind enough on the repairment costs, once again PEter, thank you). But all these issues with tubes not being reliable and all that it's REALLY making having tube amps a pain in the ass.

In the past those type of things didn't happen that often, you see old fender and marshall that still have tubes from the 70s and they work extremely well....

I'll hold on to my amps for sure, but I can definitely see an Axe Fx or some sort of "computer" in my arsenal to beat the crap out of.

 

[Fler]

Haha, thats why I have a VH4 and an AxeFX =P