Main fuse blew on my 2016X

Discussion in 'The Workbench' started by Platner, Sep 26, 2015.

  1. Platner

    Platner Member

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    I was playing through my 2061X for quite a few hours today and this evening I turned it back on to play and after a few minutes it just shut down. I checked the fuses. The HT fuse is fine but the main fuse was clearly blown; brown discoloration in the fuse.

    I went to radio shack and they had the replacement fuses. Exactly the correct type; 1.6 amp 250-Volt.

    I put a new one in but the amp still doesn't turn on. No light nada.


    Any thoughts what could cause this?

    Thanks.
     
  2. Kunnz

    Kunnz Active Member

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    Hiya Platner, I would like to add my own eperience with the mains fuse blowing and that is that usually on the older amps the main would blow because of something seriously wrong in the PSU section of the amp, that being the power XFRMR, Bridge rectifier or something very close to before the voltage has been rectified in the circuit.
    I havn't looked at, or I dont have the schematic for this model, so straigh off I cant help you without more hands on information, post the schematic if you could please. (addition) Hopefully it's not the valve heater circuit which in Marshalls and other amps that use AC voltage to heat the valves is very good, unless a valve's internal heater went bad and affected the power XFRMR.

    I would only suggest to you that if you are confident enough to open the amp up and have the right equipment like a decent DVM for example to test a few components then we could proceed further, even a good pic of the PSU section would be nice.
    If you are not confident about it, because whats up next is, you will have to disconnect several circuits to establish a true elimination process and work on mains live AC without any personal protection which is unbelievably a very risky undertaking if you are not expierienced with working upon live high voltage circuits and certianly not advisable.

    If you are then ok, we can proceed.
     
    Last edited: Sep 26, 2015
  3. Platner

    Platner Member

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    Thanks Kunnz. I took the amp over to my tech this morning. He'll sort it out. I'll post the verdict when I find out.
     
  4. Kunnz

    Kunnz Active Member

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    Good, keep us posted with what went wrong plaese.
    Good luck.
     
  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Do you have power at the wall socket?
     
  6. Kunnz

    Kunnz Active Member

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    Hey mickeydg5, Im not trying to be a wise guy here, but why shouldn't he have power at the wall socket saying he blew the main fuse? :hmm:
     
  7. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    How do you know that the utility supply/house wiring did not cause the fuse to blow?

    He only said it blew, once, and there was no other detail or explanation.
     
  8. Kunnz

    Kunnz Active Member

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    Yes mickeydg5, I know where you are coming from. Maybe a transient spike on the mains line could do that of course. Or in many circumstances the fuse was defective anyhow and was destined to go.
    Those glass fuses that they use are not the best anyhow regarding protection . A proper HRC style fuse is a better choise I think.

    Who knows yet though, lets wait and see as he said he will keep us posted. :yesway:
     
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  9. Kunnz

    Kunnz Active Member

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    On re-reading the original post with the fact that replacement fuses were used and nada, hmmmm,,,, I'm looking at something within the amp with my minds eye and I am dying to know what is the problem as I can see badness.
     
    Last edited: Sep 30, 2015
  10. Platner

    Platner Member

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    Haven't heard back from my tech yet. The amp went dead and blew the fuse in the evening after playing it and keeping it on for over 6 hours. I did check the mains and all was good, however, earlier in the morning before I turned the amp on all the electricity went out in the house for a few seconds. No storms and the development that I live in is only a few years old with all the utilities being underground.(Strange).

    I replaced the mains fuse twice and each time it blew instantly, (turned brown), light on amp never flickered or came on, not sound...nothing.

    We shall see. I'll keep you posted
     
  11. chuckharmonjr

    chuckharmonjr Well-Known Member

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    If its blowing so fast you dont even get a flicker out of the pilot light, you got a dead short somewhere. Could be tranny...could be rectifier...but something is dead to ground bolted ass fault.
     
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  12. Kunnz

    Kunnz Active Member

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    Yes Platner, It almost sounds like a mains line disaster happened somewhere and sent an awful surge down the line, I hope I'm wrong on that one as I am only assuming and maybe looking too far ahead as to what the cause was. mickeydg5 did mention that though.
    Something like that never ever happened to me on an amplifier but I have seen it on power circuits.

    Keep us posted on this one please. I would really like to know how, why and what and if the rest of the building or any of your neigbors were affected. Thanks.
     
    Last edited: Sep 30, 2015
  13. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I am not saying it was a utility issue but I try to think of everything that is likely. If it were a power surge then something in the amplifier power supply may have gotten hammered, as Chuck mentioned.

    It is weird how power surges can affect only one or two items and nothing else in the household including circuit breakers.

    It is a good idea to keep things protected from surges.

    Let us know what the technician has to say.
     
  14. Kunnz

    Kunnz Active Member

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    I'm only saying this as I know that on many SMPS power supplies that the common rail is held at half the rectified voltage.
    If the main conditioning before the final rectification and smoothing is hit hard with a transient then the whole pre fails and leads to a domino effect causing the second stage transformer to deliver whats left in a destructive way by taking out the rest of the PSU in a reverse backfire maner.

    Normally if you have a linear XFRMR in the power supply then it's not the case as it by nature acts like a soak and can handle transients that would otherwise be detrimental to the rest of the circuit.

    Most Marshall use an EI transformer I think. which are good but poor power wasters in the terms of efficency.
     
  15. Platner

    Platner Member

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    Here's an update: My tech determined that the Power Transformer blew. I went ahead and ordered both the Power and Output transformers from Mercury Magnets and also ordered two F&T filter caps figuring while the amp is apart I'll replace/upgrade everything. (Seeing the output transformers have a reputation for being problematic).

    He should be putting it back together with the new components this week. I'll keep you posted.
     
  16. Platner

    Platner Member

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    Just thought I'd give you an update on this situation as one or two folks requested:

    My Tech replaced the PT and OT with Mercury Magnetics and replaced the caps with F&T's. No more blown fuses. The right or "Bass" channel is perfect but the Left "Lead" channel starts distorting badly as the volume is turned up. He believes he has to look into the pre-amp section of that circuit. I'm confident he will figure it out.
     
  17. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Let us know. It could be a preamp tube, a component in the B+ rail or maybe even something else.
     
  18. ampmadscientist

    ampmadscientist Well-Known Member

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    "Seeing the output transformers have a reputation for being problematic..."
    No, it's the USER who plugs the amp into the wrong impedance, or uses a defective speaker cable. THAT's the REAL problem.
    Stop blaming abuse on the transformer.

    If the speaker AND speaker cable was not tested by the tech...the job is NOT complete.
    This is required. Take no chances, make NO assumptions.

    The stock transformer does NOT need to be upgraded, if it works OK.
    IF the transformer is actually BAD, then you can consider an upgrade.
    But do not waste money.
     
  19. Platner

    Platner Member

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    Hi Ampmadscientist,

    Wow! I don't know where to begin........First thing; I am an incredible perfectionist and I try and use only top quality components irrespective of cost. I am also careful and cautious to the point of insanity.

    The cable that I used to connect the amp to the cab is a made in the USA, "LAVA" brand, their "TEPHRA" premium cable. My research led me to conclude that this cable is of very high quality and I use them exclusively now.

    The cabinet is a 1996 vintage Marshall 4X12 AX with four original made in England Celestion G12M greenbacks. I am fortunate enough to live close to "Miller Sound" in Lansdale PA. The owner is considered a guru of audiophile speakers and re-coned one of the greenbacks using a Celestion brand re-cone kit. The AX tested out perfectly and the ohms were set correctly to be compatible with the Marshall 2061X head. I double, triple and quadruple checked the ohms compatibility myself and I also verified the setting with my amp tech who only lives 10 minutes away from my house.

    When I first purchased the 2061X I did a lot of research on the various forums, this one, Gearpage etc. in order to find out more about the amplifier; a normal practice in this day and age of the internet. Always nice to hear from other users; not looking for anything negative, but perhaps tips and experiences about the amplifier that might be useful to me. As I continued on with my researching a consensus began to develop, not just one or two posts, but quite a few remarking about some of the transformers in the 2061X not being of high quality and reports of failure. I did get the sense that Marshall new about this because some folks had the transformers replaced for a second and third time under warranty.

    So there you are. I'm sorry you think that it's my, (the user's), fault.

    All the best,

    Platner
     
  20. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I think its may be just a component that went awry. Check it out.
     

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