Please help JVM410H questions....

Discussion in 'Marshall Amps' started by Mateo11, Feb 16, 2020.

  1. Mateo11

    Mateo11 New Member

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    Hello everyone,

    I bought a used JVM401H the other day and absolutely love it but have some concerns and questions and could use some feedback.

    This is my 1st experience with the JVM and the amp sounds and feels amazing but here are my questions and concerns:

    1) I can not get the serial/parallel fx loop to work. Tried 2 different pedals in the loop, different cables, diff dry/wet mix settings...nothing. If I take a patch cable and hook it up to the send return I get sound. If I take 2 cables and stick one in the send and the other in the return (with no pedal inserted) and touch the 2 cables together it makes no noise. It's like the FX loop isn't even on or in the amp.

    2) The seller bought it used and said there were no mods done but can you more experienced guys look at the attached pics and tell me if it looks stock?

    3) Amp didn't come with the foot switch and is missing the back panel. There is a lot of rust too on the chassis which makes me wonder how well this was taken care of (I also have no idea if the MIDI works since I do not have the footswitch).

    Since the FX loop doesn't work the seller said he would take it back and give me a full refund. Or he said he would give me a partial refund to pay for a tech to fix the FX loop.

    I can buy another used one that is in better condition, with a foot switch and back mesh panel with JJ tubes instead of the Mullards but I am worried that maybe this one may sound and feel better because there were mods done or maybe the Mullards are better than the JJ's etc. I don't have any point of reference since this is my first JVM.

    If its bone stock I think I'll return it but if you guys think otherwise let me know. Thanks!

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  2. FracStrat

    FracStrat Well-Known Member

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    Welcome to the MAF …… I saw your post on TGP ……
    If you switch the EFX to ‘Series’ and plug in a cable to the Send ……Does the Amp Cut Out ?
     
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  3. Mateo11

    Mateo11 New Member

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    Thanks for helping FracStrat. I just tried what you said and nothing happens. No matter what I try with the FX loop nothing changes at all. Its like there is no FX loop and there are just two empty send and return inputs that lead to nothing.
     
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  4. FracStrat

    FracStrat Well-Known Member

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    Get some DeOxIt G-100 … Spray the Jacks and work um over …… ( be sure to use safe for plastic formula )
    You mentioned the rust which indicates that the jacks may be corroded …… Very High probability this is the issue……
     
  5. ampeq

    ampeq Well-Known Member

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    I to would do what FracStrat said, with all that corrosion I'm sure it's everywhere. However, unless you got a deal of a lifetime on it I would return it because of all the corrosion and missing parts. These can be had in like new cond. for about $1000 complete and the footswitch is not cheap. That unit was not cared for very well and I would think you're headed for trouble down the road. But at least you know you like it now, so all is good. Welcome to the forum!
     
  6. Mateo11

    Mateo11 New Member

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    Thanks! My only concern with getting a different like new used one is I am afraid it will sound and feel different from this one. I can not tell if any mods have been done to this one and was hoping someone here could look at the pics and tell me for sure. If it is bone stock there is no way I am keeping it and will return it back to him.
     
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  7. Mateo11

    Mateo11 New Member

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    I have tried comparing my amp gut pics to some gut pics I found on the internet and it looks like mine has much bigger blue, purple and orange capacitors...I am no amp guru or tech though so I have no idea.
     
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  8. ampeq

    ampeq Well-Known Member

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    Can you find a guitar store near by with one to try? If so set your amp to a setting you like and take a pic of it. Go to the place and set the amp the same way, try to get the same speaker config, and try your guitar to see if you like it. You can even take your amp into the store and pit them against each other with the same cab. I can't say for sure but yours looks stock, you can see where people desolder components that were originally wave soldered. And different color caps or large number of different colors is most likely just different year production. You can always "mod" a new one as well, but I don't like doing so. I think your safe in trying a newer one and would do so before ending up with a can of worms. Corrosion is a sign of moisture and amps do not like moisture very much. Sitting in a damp garage can be the death of any amp, once started it's very hard to stop it.
     
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  9. marshallmellowed

    marshallmellowed Well-Known Member

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    This may sound stupid, but do you have the Fx loop engaged (front panel control)?
     
  10. John BNY

    John BNY Well-Known Member Premium Member

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    Potentially dumb question, but have you tried pressing the FX loop switch on front of the amp to see if that does anything?
     
  11. marshallmellowed

    marshallmellowed Well-Known Member

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    I actually just asked this...
     
  12. spacerocker

    spacerocker Well-Known Member

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    I would think another JVM would sound the same. Yours is stock. Not sure what power valves are in yours, but they are different to the ones in my 2009 JVM410. Marshall have changed suppliers a few times, so that may not be significant...
     
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  13. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    1) make sure you are using the "SERIAL/PARALLEL FX LOOP" and not the "POWER AMP INSERT/SERIAL LOOP."

    2) set the "MIX" control to 100% wet. Anything less than 100% reduces signal of the "SERIAL/PARALLEL FX LOOP" so that more of the dry sound is mixed in.

    3) set the "FX LEVEL" control to -10dBV if you are using floor pedals.

    4) make sure the "FX LOOP" switch on the front panel is engaged (a red LED should be lit steady).

    5) raise the level(s) on your floor pedal(s) to 100% full blast to ensure that you are signal is coming out as loud and cleanly as possible (full/100% on the levels is just for testing purposes).

    **If none of the steps makes a difference, your last resort can be to perform a factory reset of the head. The instructions for factory reset of the head are in the JVM4 owner's manual for free download at Marshall's website. I'll cut and past the instruction for factory reset here (for clarity sake, I'll change the instructions to green font:
    Factory Reset

    This will erase all the MIDI presets and set MIDI
    reception channel to #1. Please note that once
    the memory is erased it cannot be recovered.


    1) Switch the amplifier off (power switch off, not
    standby switch).


    2) Press and hold CLEAN CHANNEL / GAIN
    switch.


    3) Switch the amplifier on (power switch on, not
    standby switch).


    4) The 4 channel LEDs will glow red.

    5) Release the switch.

    6) To confirm the factory reset press CRUNCH
    MODE switch


    If you want to abort, press any other key

    It appears to be stock/unmodified. What year is it?

    No footswitch would be a concern to me, but not a deal breaker necessarily. Missing back panel also a concern, but not a deal breaker. Rust on chassis is a concern, but depending on severity and location it might not a deal breaker. If MIDI is not working, that would be a deal breaker, but that's just me.

    I would take the owner up on his refund offer right away. To me, this amp has some questionable history and the condition you are describing sound suspect.

    You amp looks unmodified, so it should have a similar sound to another stock/unmodified 410H. Keep in mind that there are other factors that might influence a difference: bias setting, power tube brand and type, preamp tube brand and type, speaker brand/model (to name a few).

    If you like the sound of your 410H, make note of the following: bias setting, power tube brand and type, preamp tube brand and type. Then, if you decide to take it back for refund, you can buy those same types and bias to the same settings so that you get close to what you had with the previous 410H.

    Regarding the Mullards in your current amp. The Mullard will probably sound different then the JJ (I'm not sure what power tube types you're talking about). Most of the time, the power tube differences are found in low end characteristics, "feel" and response/dynamic, noise/microphonics, break up, reliabilty, and tone (sometimes). Little background: My 410H came with SED Winged =C= EL34 power tubes, which were amazing in many of the ways I listed previously. When I made the switch fo JJ E34L, I was pleasantly surprised just how similar these sound to previous SED Winged =C= EL34. Again, I'm not sure what JJ tubes are in the other 410H you mentioned, but the JJ E34L get high recommendations from me.

    If I were in your shoes, I'd return it but the decision to do as you see fit.

     
    Last edited: Feb 16, 2020
  14. Mateo11

    Mateo11 New Member

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    Thank you so much for the detailed response and help. I tried everything you mentioned and it still doesn't work. I was able to find another one available over at TGP from a forum member in really great condition with the backplate & footswitch. Has JJ's and he says everything works perfectly. I went ahead and just now bought it and working on returning this one back to the seller.

    I posted the gut pics on TGP as well and one guy responded with the following : "middle of the first pic there is 3 resistors soldered together. That doesn't look stock and pretty sure they didn't use orange drop caps."

    I would like to get your feedback and any others on what he said if you don't mind.

    Thanks!!
     
  15. Mateo11

    Mateo11 New Member

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    Thanks everyone for the replies and help so far! You guys have been extremely helpful. Much appreciated!
     
  16. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    I know that there have been some production changes at the factory between the early production years of the 410H and the current production 410H amps. I have some photos of my stock 2017 JVM410H, which is in the exact same physical state as the day I bought it brand new in 2018. Related to the comments you receive on TGP, several of my photos show the so-called "orange drop" caps (or whatever you wanna call it) which seem to be the same as what it in your amp. As far as the "3 resistors soldered together" comment you received, I don't see that in my 410H but I think I see that in yours (it's near the word "attention" on the PCB). If yours does indeed have three resistors solder together, I'm not sure how that would impact your serial/parallel effects loop.

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  17. Mateo11

    Mateo11 New Member

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    Awesome thank you! The one I just bought off a TGP member is a 2017 as well! Nice to see the similar style "Orange" drops in yours as the one I currently have. Do you think if there are 3 resistors soldered together that would affect tone? I don't see it either but in case we are missing it curious if it would be a tonal change?
     
  18. Mateo11

    Mateo11 New Member

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    I think I see what he is talking about maybe. Underneath the three blue wires in my 1st pic there appears to be three what i would call "capacitors' purple with a pink strip in the middle of each...soldered together.
     
  19. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    Hello.
    Yes, I changed my previous post to say I do see something that looks like three blue resistors solder together (if you look at the pcb near the printed word "attention" you can see what looks like three resistors soldered together). I'm not sure how that would impact the effects loop, but it might impact some other aspect such as tone-not really sure.

    But the significance of the presence of the three soldered resistors is that it seems your amp is modified, which raises the question of what else might be modified in your amp.
     
  20. Mateo11

    Mateo11 New Member

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    The post I put up at TGP was just a few pics asking if anyone could tell it the amp had been modded. I didn't mention the loop issue.

    The reason I posted it that way over at TGP is because my main concern with returning this amp back to the seller even though it poor condition & FX loop not working etc was I am afraid the amp I have has been modded a bunch and that is why it sounds and feels so good. I'm nervous a stock JVM will sound and feel completely and maybe I will be disappointed in it and unsure how to get it to the sound and feel of this one.

    The seller of the JVM I currently own says it is completely stock but I am not sure if he knows that to be 100% true. He sounds like he knows what he is talking about but he isn't the original owner either.

    I guess I'll know here in a few days when the JVM I just bought shows up at my door. Worst case scenario I would think an amp tech should be able to look at these photos and duplicate it with the new JVM if its not up to my expectations.

    I honestly thought when i was told by the seller that its 100% stock why would anyone mod these things because it sounds and feels amazing.

    With all that being said though I feel returning it is probably the safest option. I think the amp has seen a lot of abuse and while it sounds great may have issues in the future.
     
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