EOengineer
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*cough* sell the VH4 buy a Mark VII *cough*
My VH4 - not sure it is healthy - thoughts???
- Thread starter Orvillain
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Eagle
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Massive downgrade .
EOengineer
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So my tech has the amp. At first glance, there doesn't seem to be anything circuitry-wise that is wrong. There's some interesting stuff about this amp.
- The service manual implies that some of the power filter caps are mounted to the PCB. Not so on my amp. They're mounted to the chasis, and then connected to the various points required.
- He reckons the filter caps are okay. The tops of a few of them are bulging, but there's no fluid leaking from them. He's going to test them.
- There's a power supply resistor that the service manual says if it is a 2.2k rated one, replace it for a 4.7k rated one. Mine is rated for 3.3k, so ... that's odd. He's gonna replace it for the 4.7k one.
- The service manual says that the NFB should be connected to the 8ohm tap, but mine is connected to the 4ohm one. He's gonna switch that over.
- All of the screen grid resistors check out okay.
- There's no uneven discolouration on the KT77 valves, but he's going to test them. Also I'm going to purchase a matched quad of 6L6's or EL34's to try in the amp.
- He's gonna test the preamp valves too.
There's really nothing awry with the amp at first glance.
- The service manual implies that some of the power filter caps are mounted to the PCB. Not so on my amp. They're mounted to the chasis, and then connected to the various points required.
- He reckons the filter caps are okay. The tops of a few of them are bulging, but there's no fluid leaking from them. He's going to test them.
- There's a power supply resistor that the service manual says if it is a 2.2k rated one, replace it for a 4.7k rated one. Mine is rated for 3.3k, so ... that's odd. He's gonna replace it for the 4.7k one.
- The service manual says that the NFB should be connected to the 8ohm tap, but mine is connected to the 4ohm one. He's gonna switch that over.
- All of the screen grid resistors check out okay.
- There's no uneven discolouration on the KT77 valves, but he's going to test them. Also I'm going to purchase a matched quad of 6L6's or EL34's to try in the amp.
- He's gonna test the preamp valves too.
There's really nothing awry with the amp at first glance.
deadpool_25
Roadie
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deadpool_25
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laxu
Rock Star
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Sounds like a lot of stuff that might have been tweaked a bit on the circuit over time?
MirrorProfiles
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If they’re bulging they’re probably dried out and should be replaced. I’d just do it anyway given the age of the amp, cheaper than a repair if one goes.
My tech replaced some in an old Marshall a while back - no bulging but dried out and gunky inside.
Curious if he finds anything, and whether you like the amp with more NFB.
My tech replaced some in an old Marshall a while back - no bulging but dried out and gunky inside.
Curious if he finds anything, and whether you like the amp with more NFB.
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This is going to make a difference!
Eagle
Rock Star
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It doesn’t sound in the clips like a typical VH4. One problem you get these days is when a component is “in tolerance “ most amp techs go “ fixed “ even if it sounds like shit compared to originally. Quite a lot a companies cherry pick certain parts to tighter specifications than the companies that make them to be within. Even Marshall do this.
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This amp isn't a typical VH4, is the issue here. The schematic which Peter sent me (no I can't send it to anyone!) clearly says that there is a lot of component differences between 1992-2005. Anything after that date range is much more standardized. Before that.... definite differences.
Mine is closer to your 95/96 blueface model, from what I can gather. It just happens to have a silver face plate.
So while I am not expecting it to match a modern model exactly, I would certainly like it closer.
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My tech has replaced the 3.3k resistor with the recommended 4.7k, and he has replaced the KT77's - which all checked out fine, but were more like two matched pairs, rather than a matched quad. Suspect when I bought them they were never a quad, and I put them in without checking. Oopsie number one. Then he said the bias was very high! I followed the service guide exactly, so I'm guessing it drifted at some point. But possibly oopsie number two on my part as well.
I had him put JJ 6L6GC's in there, and I'm loving how it sounds. Proper roaring "Marsha"-esque tones, but obviously with the Diezel flavour. It no longer sounds fuzzy and flubby, like a Big Muff!!!
He also moved the NFB to the 8ohm sockets. It was 4ohms from the factory from what we could tell.
Amp roars like a demon now!
I had him put JJ 6L6GC's in there, and I'm loving how it sounds. Proper roaring "Marsha"-esque tones, but obviously with the Diezel flavour. It no longer sounds fuzzy and flubby, like a Big Muff!!!
He also moved the NFB to the 8ohm sockets. It was 4ohms from the factory from what we could tell.
Amp roars like a demon now!
EOengineer
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Eagle
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Excellent
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Hells yeah!Yeah but does it tool?
TSJMajesty
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I'm curious which change you think is responsible, or most responsible, for making it sound right?
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Oh man, I'm just an edgelord dildo who can't even bias an amp correctly it seems. I have no idea!!!
I will say, that even though I now have 3 6L6 based amps - the Mark V, Recto MW, and now the VH4.... they all sound REALLY different from one another. So I don't think the power tubes are making a huge difference to the tone.
