#1
Recently bought a Marshall JVM410H secondhand in excellent condition, amazing amp.

The only thing that let me down was just over the past couple days, the volumes of the channels were unbalanced (the clean green/orange has considerably less volume than clean red) and also the gain was also cut back quite a lot.

This happened after attempting the 4 cable method (which failed) and having the amp left on standby for a considerable amount of time.
I had a small peak into the vent and saw that 2 of the power tubes (I think? The big ones right?) had been previously replaced.

The valves all still glow orange when in operation.

I'm taking as a valve issue, could someone confirm this or suggest other problems that could have occured?
#3
This happened to me with a YCV40. Power tubes needed changing. I used to leave it on standby in between sets at gigs weekly. My guess was that it was a result of cathode poisoning.

Does the clean channel have a lack of headroom as well?

Check that first preamp valve (V1) that's usually the first gain stage associated with all the channels.
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Mesa Mark IV
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#4
I got a 410h too. Remember that the clean channel is one of the 4 channels. Green, Orange, and Red aren't channels, but rather gain stages for the same channel.

The Red is supposed to be more gain (and probably louder) than the Green and Orange stages. The Orange should have more gain than the Green.

It should be that way for all 4 of your channels.

So if you haven't already, see if you can find a new one on display in a store and compare it before you decide you really have a problem.

Also, have you downloaded the manual from Marshall if it didn't come with one?

Here's what the manual has to say about the Clean channel:

1. CLEAN CHANNEL
CLEAN GREEN MODE: This is the cleanest of the three modes and, in keeping with traditional
clean amps it uses a simple and straightforward circuit, keeping the signal as pure as possible.
In this Mode the channel’s Volume control is taken out of circuit as is the case in vintage
amplifiers of this nature. This is the only JVM mode where this happens.
CLEAN ORANGE MODE: By adding another gain stage after the tone stack we get a
punchier sound that’s easy to overdrive. As in the rest of the modes the channel's Volume
control is now active.
CLEAN RED MODE: This mode pushes the original clean sound even more and transforms
itself into a pseudo high gain channel with the addition of yet another gain stage after the tone
stack.
In keeping with the classic clean amps of yesteryear, all three modes of this channel feature what is known as a pre-gain tone stack
(i.e. the tone network lies before the channel's main gain stage). The reverse (i.e. the tone
network being after the main gain stage) is typical of most Marshalls and, as a result, the
Clean channel's tone controls work in a slightly different way than you might expect. In addition
to controlling the tone of the channel they also affect how it reacts in terms of gain, allowing
you to shape how the signal distorts. For example, turning up the Middle control on higher Gain settings will focus the distortion there, making your sound ‘sing’ in a traditional
blues/rock way. Also, because of the channels’ ‘tone then gain’ topology, when a lot of gain is
dialled in (especially in the case of the RED mode), it may appear that its tone controls aren't
doing as much as you’d expect or sound over distorted. This is because the signal is being
distorted after the tone stage, minimising the effectiveness of the Bass, Middle and Treble
controls.

Good luck!
#5
BTW, you can rule out the power amp by hooking the XLR out to a PA, mixing board, or whatever and keep the switch on standby. That bypasses the power amp section. If it still behaves the same, then it's definitely not the power tubes.

Hey, Reincaster, is your Traynor modded? I didn't think those had with 3 gain stages for the clean channel... If not, then your amp can't be doing what the TS's is doing. I mean, it's got a boost for the dirty channel, and a bright switch for the clean channel (or do they work on both channels?)--and the clean channel doesn't even have a gain control. Anyway, stock, they're configured so differently from the JVM that you couldn't have had the same symptoms TS describes.
#6
It happens on all of the channels.
The green for all the channels is just low (on volume)

The gain loss is apparent in all channels, there isn't much noticeable difference between the channels.
The OD2 Red sounds more like a crunch.
Last edited by DiminishedShred at Oct 28, 2011,
#7
Quote by jetwash69
BTW, you can rule out the power amp by hooking the XLR out to a PA, mixing board, or whatever and keep the switch on standby. That bypasses the power amp section. If it still behaves the same, then it's definitely not the power tubes.

Hey, Reincaster, is your Traynor modded? I didn't think those had with 3 gain stages for the clean channel... If not, then your amp can't be doing what the TS's is doing. I mean, it's got a boost for the dirty channel, and a bright switch for the clean channel (or do they work on both channels?)--and the clean channel doesn't even have a gain control. Anyway, stock, they're configured so differently from the JVM that you couldn't have had the same symptoms TS describes.


I've never had a JVM, so I thought the colors of the channel were like the mesas, not different voicings of the same channel.

But as far as symptoms, my clean channel had no headroom at all, but was still loud, but 1/2 the volume of the drive channel, which I think is too big of a difference actually.
Peavey 5150
Mesa Mark IV
Mesa Single Rectifier (Series 1)
Fender Custom Shop Tonemaster
Roland Microcube

-Whitebox OS 1x12
-Port City OS 1x12

Digidesign Eleven RackAxe Fx Ultra
#8
OK, if OD2 Red sounds like crunch, then something's wrong

OD2 Red should knock down walls.

Crunch Orange with the MV set to 6 and channel volume/gain dimed literally knocks books off my bookshelves with my 1960 4x12 cab.

I bet it's doing the same through the XLR. Doesn't sound like a power tube issue to me unless the problem "goes away" when you use the XLR out with the amp on standby.
Last edited by jetwash69 at Oct 28, 2011,
#9
Quote by Reincaster
I've never had a JVM, so I thought the colors of the channel were like the mesas, not different voicings of the same channel.

But as far as symptoms, my clean channel had no headroom at all, but was still loud, but 1/2 the volume of the drive channel, which I think is too big of a difference actually.


No harm, no foul. I'm less familiar with the Mesas. I've played around with a Mark IV and a Triple Rec for less than an hour each.

Your Traynor is a great amp, by the way. It just serves a very different purpose than the JVM...

Take care.