HUM IN MARSHALL JVM 410 JS OR GROUND PROBLEMS?

[Leonard Neemoil]

 

[Darthslater]

NO PROBLEM

 

[Moony]

Just for the record, would you care to snap a gutshots pics of the JS?

Please take a look here > Klick <

 

[Darthslater]

MY FILES ARE TO LARGE.....BUT I CAN TELL YOU THERE ARE BOARDS IN THERE THAT ARE NOT IN MY STANDARD 410

 

[Darthslater]

View attachment 111222

GRACIOUS MY ASS.....SOMEBODY MADE A SMART ASS COMMENT AND I RESPONDED...I SEE THAT IS A COMMON THING ON THIS FORUM, LOOK IF ANYBODY DOESNT LIKE MY POSTS OR FEEL THEY HAVE TO BE A "SMARTASS" AND I USE SMART IN THE LOOSEST WAY...JUST KEEP SCROLLING, I DON'T HAVE TIME FOR THE BULLSHIT.

 

[Moony]

BUT I CAN TELL YOU THERE ARE BOARDS IN THERE THAT ARE NOT IN MY STANDARD 410

There is one separate board for the jacks of the speaker outs, effect loop, midi etc. - not a big deal at all.

 

[Darthslater]

I KNOW SANTIAGO COMES HERE FROM TIME TO TIME IT WOULD BE NICE TO HEAR WHAT HE HAS TO SAY ABOUT THIS, MY OTHER BANDMATE ALSO HAS ONE WE LIVE 300 MILES APART HE LIVES IN DETROIT AND HAS HAD HIS AMP IN TO SEVERAL TECHS OVER THE YEARS FOR VARIOUS THINGS MOSTLY BIASING AND THEY ALL SAY THEY HAVE NEVER SEEN ANY MARSHALL LIKE THESE....WHICH TO ME IS A PROBLEM....ALMOST LIKE ASKING A PLUMBER TO FIX YOUR HOUSE WIRING.

 

[Moony]

THEY ALL SAY THEY HAVE NEVER SEEN ANY MARSHALL LIKE THESE

The JVM HJS is not that different from a regular JVM.
And the JVM is Marshall's flagship amp since 15 years now.
In Europe it's a topseller and well known among amp techs.

But it's much more expensive in the US, so not as many guys have one there as in the EU or UK - and techs don't see them so often therefore.
However the schematics of both, the regular JVM and the Satriani version, are available on several forums (at least they were for a long time).

 

[PelliX]

Please take a look here > Klick <

Oh boy, Tony. I'm not going to lay into him here again, but ... geesh, he likes to hear himself talk



At least he concurs that it's basically the same. I'm not a JVM guy myself, nothing against them, though. I can't help thinking that this is what would have happened if Mesa Labs and Marshall had a love child, though. Decent kit, but *packed* with extras to an extent that boggles the mind.

There is one separate board for the jacks of the speaker outs, effect loop, midi etc. - not a big deal at all.

Yup. Are those Samwha 85C electrolytics? Marshall.... c'mon. This is not a budget amp.

AND THEY ALL SAY THEY HAVE NEVER SEEN ANY MARSHALL LIKE THESE....WHICH TO ME IS A PROBLEM....ALMOST LIKE ASKING A PLUMBER TO FIX YOUR HOUSE WIRING.

You've made your point. I think. You can stop shouting now, we can all read lower case. Anyhow, it's more like asking your electrician to put in two light switches for your hall light instead of just one. And perhaps a motion sensor.

Just snap us some gutshots, tell us what the problem was, and we can perhaps pass that on to the next poor soul in need of a fix.

 

[Moony]

Oh boy, Tony.

I know... but he filmed the interior so I think it was worth posting it.

Are those Samwha 85C electrolytics?

The electrolytic caps and the red polypropylene caps are from Samwha, yes - but nothing wrong with them imho.
What I've found to be interesting is that in the HJS the .022 coupling caps are the grey polyester caps - in the regular JVM Marshall used the red polypropylene - which may be more suited for a modern hi-gain amp. I had replaced them with MKT1813 on mine.

 

[spacerocker]

GRACIOUS MY ASS.....SOMEBODY MADE A SMART ASS COMMENT AND I RESPONDED...I SEE THAT IS A COMMON THING ON THIS FORUM, LOOK IF ANYBODY DOESNT LIKE MY POSTS OR FEEL THEY HAVE TO BE A "SMARTASS" AND I USE SMART IN THE LOOSEST WAY...JUST KEEP SCROLLING, I DON'T HAVE TIME FOR THE BULLSHIT.

Silly of me....now it has been explained to me in block capitals, I can see I was wrong! I have worked on JVMs, I know the schematics inside out, I have an electronics degree - but now I have seen the block capitals, and the calm, reasoned arguments, I can see the error of my ways...

Santiago wouldn't waste his time commenting on such trivia!


<<mental note: Next time Darthslater wants help or advice, he might have a long wait....>>

 

[PelliX]

I know... but he filmed the interior so I think it was worth posting it.



The electrolytic caps and the red polypropylene caps are from Samwha, yes - but nothing wrong with them imho.
What I've found to be interesting is that in the HJS the .022 coupling caps are the grey polyester caps - in the regular JVM Marshall used the red polypropylene - which may be more suited for a modern hi-gain amp. I had replaced them with MKT1813 on mine.

As someone who does a fair deal of upkeep on electronics I know that electrolytic caps are often one of the first things to go in a circuit and I keep a vague mental tab on brands. Some like Samwha and CapXon, etc left a bad taste in my mouth (no, not literally... yuck). They may well go on for years, but anyone putting a large 85C rated electrolytic in a valve *combo* is on the dodgy side of bold, IMHO. I'm not sure why Marshall flip-flop a bit between polypropylene and polyester in their amps... price and component availability perhaps. If they wanted to invest a few pounds into upgrading components I'd start with the Samwhas and perhaps full size pots. Still, a welcome adjustment in my book!

 

[Moony]

They may well go on for years, but anyone putting a large 85C rated electrolytic in a valve *combo* is on the dodgy side of bold, IMHO.

I never thought about swapping them.
-40 to 85°C is quite a common rating for electrolytic caps, even the F&T caps everyone loves here have the same rating: https://www.tube-town.net/ttstore/bauteile-10662/kondensatoren/f-t-kondensatoren/
And that doesn't mean they completely fail if its a few degrees more of heat.

price and component availability perhaps. If they wanted to invest a few pounds into upgrading components I'd start with the Samwhas and perhaps full size pots.

I swapped the film caps and replaced the ceramics and some silver micas with nicer 2kV Vishay and Murata ceramics (and some NOS 470p for treble caps).
The pots are ok, I never had a problem with one - and if so, I would just replace it. Luckily the parts are available.
Even if someone can't solder, in worst case he could just buy a new front pcb which was around 120 Euros a few years ago - which probably is similar in cost what a tech would charge for a repair.

 

[Darthslater]

SINCE SOME ON HERE ARE SO WORRIED ABOUT MY CAPS, KNOW THIS THEY ARE STUCK ON.....I PROBABLY WONT COME HERE FOR ANYMORE ADVICE TO MANY DUMBASS'S WITH OPINIONS

 

[Moony]

SINCE SOME ON HERE ARE SO WORRIED ABOUT MY CAPS, KNOW THIS THEY ARE STUCK ON.....

Do you mean the hot glue around it?
This is primarily used to prevent them from falling off the pcb when soldering the legs by the machine.

 

[PelliX]

I never thought about swapping them.
-40 to 85°C is quite a common rating for electrolytic caps, even the F&T caps everyone loves here have the same rating: https://www.tube-town.net/ttstore/bauteile-10662/kondensatoren/f-t-kondensatoren/
And that doesn't mean they completely fail if its a few degrees more of heat.

True, but the F&T caps are generally mounted externally, not directly above a set of output valves. 85C will generally degrade/die faster than a 105C cap - rule of thumb, but certainly when heat is a substantial factor.

The pots are ok, I never had a problem with one - and if so, I would just replace it. Luckily the parts are available.

Sure, though sourcing the right one can be a pain sometimes, hehe.

 

[PelliX]

Do you mean the hot glue around it?
This is primarily used to prevent them from falling off the pcb when soldering the legs by the machine.

Actually it's got more to do with the vibrations during use and transport than the assembly/manufacturing process.

SINCE SOME ON HERE ARE SO WORRIED ABOUT MY CAPS, KNOW THIS THEY ARE STUCK ON.....

We've noticed. You could press the Caps Lock button again, which in general should disengage from that mode, indicated by a light on your keyboard. Oh, wait, you're talking about capacitors?

 

[Chris Banuelos]

Why you being a dick when people are trying to help? If you don’t want opinions then don’t ask, cornball.

 

[Chris Banuelos]

SINCE SOME ON HERE ARE SO WORRIED ABOUT MY CAPS, KNOW THIS THEY ARE STUCK ON.....I PROBABLY WONT COME HERE FOR ANYMORE ADVICE TO MANY DUMBASS'S WITH OPINIONS

Good riddance

 

[El Gringo]

PREFACE: Which type of tube went bad. Preamp or Power. If Power tube it could have left a carbon trail from an arc causing a plethora of issues. If Preamp tube there are some trouble shooting measures below.

1.) Was the amp under warranty?

2.) Why accept it from the Technician who didn’t repair it properly in the first place?

3.) Take it back and tell them to repair the amp properly. (Can we have the name of the company or individual who did the presumed poor job)? [See my point? They will not want that kind of exposure].

Trouble shooting if you choose to ignore 1-3:

A.) With a known good “instrument” cable plug your guitar in to the effect loop Return. You should get a very loud clean signal through your cabinet.

(This will cut the trouble shooting work load in half as it will tell us if the anomaly is in the preamp or power amp section of the amp. I am guessing preamp as you stated the clean channel is pristine.

B.) Regardless of being new tubes I have received bad new preamp tubes. Example: A 12AX7 preamp tube is a dual triode, that is to say two stages in one glass enclosure. I have not only had one side be noisy but one side entirely not working with new tubes.

Most people are not aware but side B of the tube (pins 6/7/8) were designed to have a quieter signal to noise ratio.

Take a known hood 12AX7 then one by one starting from one side of the preamp tubes pull one and replace with the known new good tube. If issue persists reinstall the tube, move to the next tube etc…

Once you have answered these questions for we who are willing to assist you & completed the tube rolling trouble shoot we can go from there.

It sounds as if a important ground has come loose or some has accidentally or buy human error created a ground loop.

Best Regards, David

You are very wise and your knowledge is immense !