JVM knobs

eddyrox

eddyrox

Active member
Just tried a JMV410H. WOW. YES! It's definitely what everyone says it is.

However, the knobs on the JVM (I was playing) had a lot of "play", that is, they didn't "feel" mounted to the chassis.

I know that they are mounted to the PCB's, but the stems had a lot more "play" than I am used to. By "play", I mean that the knob stems felt like they were floating and could be pushed left/right and up/down without any fight.

Anyone else?
 
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eddyrox":4fd01 said:
Just tried a JMV410H. WOW. YES! It's definitely what everyone says it is.

However, the knobs on the JVM (I was playing) had a lot of "play", that is, they didn't "feel" mounted to the chassis.

I know that they are mounted to the PCB's, but the stems had a lot more "play" than I am used to. By "play", I mean that the knob stems felt like they were floating and could be pushed left/right and up/down without any fight.

Anyone else?
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Sup Bro!!

I have to admit that I have felt that on one but not on another. Im not sure if its a luck of the draw thing? Some seem to be put on tighter then the others. that said, It would not bother me at all as long as the sucker doesn't come off or break! I freaking love that amp!
 
Probably have plastic shafts. Might also see if you can tighten the shafts and the knobs, loose ones can do that too.

Pete
 
Welcome to the world of cheamp, Chinese import plastic shafted pots mounted to a flimsy PCB. It's cheap, fast and easy to manufacture. That doesn't mean it's the best way to do things.
 
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Gainfreak":31b85 said:
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Sup Bro!!

I have to admit that I have felt that on one but not on another. Im not sure if its a luck of the draw thing? Some seem to be put on tighter then the others. that said, It would not bother me at all as long as the sucker doesn't come off or break! I freaking love that amp!
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Ralph! thanks.
Hey when are you going to "buck up" and get an Anderson?!?! :poke: :D
mike
 
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stratotone":f22b4 said:
Probably have plastic shafts. Might also see if you can tighten the shafts and the knobs, loose ones can do that too.

Pete
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Pete and Carl, thanks for the information!
mike. :thumbsup:
 
They are not chassis mounted - they are PCB mounted, with no support.

They are also plastic-shaft pots, where the plastic shaft goes through a hole in the chassis.

The knobs pull off easily, and are the same type as those used on the MG's...

If there was a complaint I would have about the construction used, this would be it.

But, since I treat my gear like gold, I don't think I'll have a problem with it.
 
The term my company uses for what you are describing is shaft wobble. It is due to the POTS not being properly supported and/or the shaft being too long. With that many knobs on an amp, my guess is some knobs have it and some don't. I work on Appliances and I see it and we have alot fewer knobs or encoders....
 
They will likely eventually break loose from the PCB, I've seen this happen quite a few times on some older Marshalls with this construction. It's not to hard to solder them back on; I’ve done it a few times. But due to the complexity of the JVMs layout, it may be another story with them. :cry:
 
If I owned one of these I'd definitely keep it in a nice flight case.
A lot of mass production stuff is delicate because of the way it's made nowadays....unfortunately.
But we want stuff cheap, so cheaply it will be made. ;)
 
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carlygtr56":de515 said:
Is this any different then the DSL and TSLs?
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TSL/DSL have pots that are mounted to a PCB, but have a supporting nut that bolts the pot to the chassis.

These don't - these are basically PCB pots, that have a plastic shaft that goes thought a hole in the chassis - there's no "chassis" to the pot itself, which is what the nut would go on.

I think it's also due to the compliance thing. I'm betting standard pots aren't complaint, at least, yet.

This is a good question for Santiall.
 
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Greazygeo":96cf8 said:
I think this method of construction is due to RoHS compliance.
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RoHS doesn't dictate component mounting or construction techniques, only the content of those materials deemed hazardous. For example, the PEC mil-spec 2W sealed chassis-mount pots I use in my amps are RoHS-compliant, and they are the farthest thing from flimsy you'll find. Marshall chose those strictly for ease of manufacturing and low cost.

Randall Aiken
 
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Greazygeo":6cc3f said:
:|::QBB:Maybe they are not compliant.
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I think it comes down to how the pots are mounted.

RoHS might only apply to PCB's, which, in the JVM's case, includes the pots. With other amps, since the pots aren't part of a PCB, they can use a non-compliant RoHS item, and still be RoHS complaint

That being said, I don't know how RoHS Complaince works - I'm just guessing :)
 
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kannibul":dc3b6 said:
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TSL/DSL have pots that are mounted to a PCB, but have a supporting nut that bolts the pot to the chassis.

These don't - these are basically PCB pots, that have a plastic shaft that goes thought a hole in the chassis - there's no "chassis" to the pot itself, which is what the nut would go on.

I think it's also due to the compliance thing. I'm betting standard pots aren't complaint, at least, yet.

This is a good question for Santiall.
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Correct, the DSL/TSL had cheap and flimsy PCB mounted pots but the daughterboard with the pots was somewhat stabilized by the screws. The new JVM took things to a new level of cheapness for an expensive amp. The answer is going to be obvious - Marshall crammed a lot of technology into an expensive amp and they had to control costs.

Since 99% of the people who buy guitar amps will never leave their bedroom with them it makes sense to cut the costs and deal with the warranty issues. The pro level musicians that do tour with this mass produced gear can afford to have multiple backups on hand so the reliability issue isn't a deal breaker for them as long as it's not constantly breaking.

Smaller manufacturers can't deal with the repairs and don't have an acceptable failure rate so they build things to much higher quality standards, but their time and materials causes the cost to rise. It's a trade-off.

Time will tell how the JVM holds up to heavy gig use. I'll be looking for a cheap used one when the honeymoon era is over, I really like the concept and the clips I've heard so far.
 
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raiken":2310c said:
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RoHS doesn't dictate component mounting or construction techniques, only the content of those materials deemed hazardous. For example, the PEC mil-spec 2W sealed chassis-mount pots I use in my amps are RoHS-compliant, and they are the farthest thing from flimsy you'll find. Marshall chose those strictly for ease of manufacturing and low cost.

Randall Aiken
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I'd rather pay a bit more and have the knobs and tubes mounted in a more durable way/construction method. ;)
I'm not saying I wouldn't own a JVM...and they aren't the only mass produced amp making amps this way...how will this method of production withstand gigging/loading night after night?

We shall see...

I give props to the handmade amp builders. :thumbsup:
 
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kannibul":381ce said:
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I think it comes down to how the pots are mounted.

RoHS might only apply to PCB's, which, in the JVM's case, includes the pots. With other amps, since the pots aren't part of a PCB, they can use a non-compliant RoHS item, and still be RoHS complaint

That being said, I don't know how RoHS Complaince works - I'm just guessing :)
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No, that's not true. RoHS compliance involves the entire product, and has nothing to do with construction techniques, only the materials used in the components.

Randall Aiken
 
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The Big Snit":7463f said:
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I'd rather pay a bit more and have the knobs and tubes mounted in a more durable way/construction method. ;)
I'm not saying I wouldn't own a JVM...and they aren't the only mass produced amp making amps this way...how will this method of production withstand gigging/loading night after night?

We shall see...

I give props to the handmade amp builders. :thumbsup:
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I'm with you, I'd rather pay a little more and get higher quality, but where does a big company like Marshall draw the line? If they added just a "little more" to the price for every compromise they made (cheap jacks and pots, poorly mounted PCBs for pots, PCB mounted tubes, etc...) pretty soon they end up with a $4K amp that everybody wants and few can afford.

Every $1 they add to their manufactuing cost adds $5 to what we pay, so $50 worth of manufacturing improvements makes the amp $250 more expensive. This is true for amps, cars, houses, electronics, everything that is manufactured or constructed. There comes a time when the builder has to draw a line and accept certain compromises. Let's just hope Marshall got it right and didn't compromise in areas that will affect reliability.
 
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