Diezel VH4 issues (Any certified techs in Toronto?) Please help

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boogie1

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I'm having major issues with my beloved Diezel VH4.
Several weeks ago the sound/signal just suddenly cut out for no reason, with none of the usual forewarning from bad tubes.
I replaced all of the pre-amp tubes, and still nothing. I plugged into the return and there was some signal, so the power tubes are fine.
It's now with a local tech, where it's been for almost a month, with no resolve.
He's tested all of the tubes, and they're all fine. He said that the signal disappears before the send, but the power section is fine.
Unfortunately he doesn't have experience with Diezel amps. He said that he's reached out to Diezel but hasn't received enough info to identify and resolve the issue. If anyone has any suggestions or advice please let me know, I would appreciate it very much.
 
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Is the issue happening when you are just using the amp (no effects plugged into effects loop)? Or do you use effects going into the effects loop Send/Return?
Is the sound missing on all channels? Or just one, two, or three? Is it worse on any channel/s in specific?
 
VHTStark said:
Chris Church is a certified Diezel tech. Located in Hamilton.
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Yes, Chris has previously serviced two of my Diezel's. He seems to be the only tech with the proper knowledge to work on Diezel's within the greater Toronto area. The problem is that he's always so slammed with work and a little too far from me.
I'll be reaching out to him this week.
 
Ultradeaf said:
Is the issue happening when you are just using the amp (no effects plugged into effects loop)? Or do you use effects going into the effects loop Send/Return?
Is the sound missing on all channels? Or just one, two, or three? Is it worse on any channel/s in specific?
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The issue is happening when I'm plugged straight in with no FX's in the loop.
The sound is missing on all four channels. The only way to get any sound / signal is by plugging into the return of the FX loop.
 
You're going to need a tech- familiar with Diezels- to determine exactly what is wrong with the input or power section in your amp. And hopefully it's something that can be replaced.

The only thing that really complicates the VH4 is the use of magnetic relays/MIDI control. I would think so long as whoever is looking at the amp is able to determine where signal is travelling in the amp, they can determine where it is NOT and therefore where the issue lies.

Have you tapped around on the outer chassis of the amp- while it is on- with a non-conductive stick to see if any components have gone bad and became microphonic? The closer you get to a microphonic component, the louder the tapping will be amplified. Sometimes that is an easier way to determine where a failing component is located. But if amp is dead, obviously you won't be able to hear.

What year is your VH4?
 
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Midi Chip could be scrambled and does not know what to do.
Also, depending on the year there is an internal fuse on the main board and two fuses on the midi board.
 
rickenbacker198 said:
It sounds like a bad contact in the loops jack? I believe the signal gets sent there regardless of being plugged in or not.
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Tried jumping the serial loop?
I mean go from send to return with a short cable without fx in between.
 
Ultradeaf said:
You're going to need a tech- familiar with Diezels- to determine exactly what is wrong with the input or power section in your amp. And hopefully it's something that can be replaced.

The only thing that really complicates the VH4 is the use of magnetic relays/MIDI control. I would think so long as whoever is looking at the amp is able to determine where signal is travelling in the amp, they can determine where it is NOT and therefore where the issue lies.

Have you tapped around on the outer chassis of the amp- while it is on- with a non-conductive stick to see if any components have gone bad and became microphonic? The closer you get to a microphonic component, the louder the tapping will be amplified. Sometimes that is an easier way to determine where a failing component is located. But if amp is dead, obviously you won't be able to hear.

What year is your VH4?
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Thanks for the reply.

No weird noise issues at all. I finally brought it home last week, the tech had it for over a month and didn't identify or resolve a thing, he was horrible. I'm taking it to another tech this weekend and hoping for the best.🙏

It's a 2018.
 
MARK2C said:
Midi Chip could be scrambled and does not know what to do.
Also, depending on the year there is an internal fuse on the main board and two fuses on the midi board.
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Thanks for the info, I'll past that along to the new tech. It's a 2018 VH4
 
I'd expect that a tech would come up with that idea by himself. ;-)
You could also check going out of the preamp into the return of another (power) amp to see whether the Diezel preamp is actually giving out a signal.
If your current tech did not check that, he should switch jobs. So I guess he has already checked that.
 
Vin Diezel said:
I'd expect that a tech would come up with that idea by himself. ;-)
You could also check going out of the preamp into the return of another (power) amp to see whether the Diezel preamp is actually giving out a signal.
If your current tech did not check that, he should switch jobs. So I guess he has already checked that.
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I tried jumping the loop(s), nothing...

The pre-amp is giving signal, you can also hear the gain in channel's 2-4 if you turn the master volume to 2-3 o'clock.
There's just very, very faint volume. I thought it may have been an issue with the master volume pot, it was a little scratchy. The tech said it was fine.
I honestly believe that he didn't even work on it in over a month. He was actually upset that I took it back. It's astounding how many people lack work ethic and proper business etiquette these days.🤦‍♂️

Hopefully I'll have better luck with the new tech this Saturday.
 
That is perfectly normal. The gain comes from the preamp. Can you go out of the Diezel preamp into another power amp?
I think it might be faulty jacks.
 
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