amp died

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HootsmonHootsmon Frets: 15924

Past 2 or 3 night there were intermittent short periods of dying volume, rising and falling, then it was OK for an hour or two

Same thing for 3 nights....changed what I thought was a faulty lead and it stopped  " ah, it's a bad lead" I thought to myself

Tonight the poor bugger died on me...stone dead, lights work but that's all

Laney VC15 I have a couple of spare preamps but that's it. Could a preamp be responsible you think?

Will have a look Sunday, ,,any thoughts?

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Comments

  • Could be a faulty output valve which takes out the ht fuse. This has happened to my mates lc30 on a few occasions. I would wait for the experts sound advice first though!
    The Swamp City Shakers
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  • ICBMICBM Frets: 71955
    Do the valves light up?

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • SnagsSnags Frets: 5326
    I had a similar issue on my Lionheart recently - turned out to be shot soldering on the impedance selector switch, which surprised everyone.
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  • ICBMICBM Frets: 71955
    edited June 2018
    Snags said:
    I had a similar issue on my Lionheart recently - turned out to be shot soldering on the impedance selector switch, which surprised everyone.
    Having worked on Laneys, it doesn’t surprise me at all... it’s something I’ve come across several times on them, including a Lionheart with a connection that had never been soldered on one of the power valve sockets - wire just loose in the hole, no solder on it.

    To be fair, I fixed a Mesa with a cold solder joint this week too.

    As far as I know this model doesn’t have the notorious thermistor, so it could be a preamp valve, solder joint, failed resistor, or if you’re unlucky the output transformer, in about that order of probability.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • HootsmonHootsmon Frets: 15924
    thanks guys...will have a look on Monday
    tae be or not tae be
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  • ecc83ecc83 Frets: 1589
    edited June 2018

    I had an A30 with a dry joint on an EL84 heater pin. The 84 stayed lit but the dry was the feed to the PI and rest of pre amp so when it faded out a quick boggle seemed to show valves still alight!

    As almost always, one off.  But! You can be sure someone in Korea got a bollicking!

    Dave.

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  • HootsmonHootsmon Frets: 15924
    edited June 2018

    UPDATE 1

    took the amp into the kitchen for a look see.....

    the two power valves and three pre amp valves all had the orange glow 

    Plugged a guitar cord into the front and it's working today!

    Will play guitar minus FX through it tonight and see how it goes

    From dead as a Dodo to working again....!

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  • HootsmonHootsmon Frets: 15924
    edited June 2018

    UPDATE 2

    Played tonight two hours straight into amp and there was no problem at all! 

    jeez

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  • ICBMICBM Frets: 71955
    Probably a bad solder joint.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • HootsmonHootsmon Frets: 15924
    edited June 2018

    Latest

    played for 1 hour tonite no problem........suddenly stopped workin'

    Pilot light still on but all 5 valves no lighty

    tae be or not tae be
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  • ICBMICBM Frets: 71955
    Filament circuit failure. If it doesn’t have a thermistor - it’s not shown on the schematic I have, but I’m not sure if there any revisions - then it will probably be a bad solder joint. If there is a thermistor, it will be that.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • DJH83004DJH83004 Frets: 196
    Never seen one with a thermistor IC, but could be a later revision, they normally have a 5 amp fuse fitted, so could be something as simple as a loosely fitting fuse, or a bad joint on the fuse holder. 
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  • HootsmonHootsmon Frets: 15924
    Thanks guys......is it something that a noob like me could fix or is it a shop job?
    tae be or not tae be
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  • DJH83004DJH83004 Frets: 196
    edited June 2018
    hootsmon said:
    Thanks guys......is it something that a noob like me could fix or is it a shop job?
    Personally I would have to say that you could remove the amp from the chassis and check to see if the fuse is secure, or hasn’t now actually blown, but after that off to your local tech I’m afraid.

    EDIT: Having looked at a number of other forums, Laney clearly did fit PTC polyswitches at some stage in the heater circuit, so the ones I have worked on were either early models or had already been converted to fuses. In any event I suggest it is definitely a visit to your local tech. 
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  • ICBMICBM Frets: 71955
    Update on this - it was a polyswitch (thermistor) failure... they must have "improved" the model, unfortunately.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • jpfampsjpfamps Frets: 2723
    ICBM said:
    Update on this - it was a polyswitch (thermistor) failure... they must have "improved" the model, unfortunately.

    Might be to conform with the regs re fuses blowing on transformer secondary shorts.


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  • ICBMICBM Frets: 71955
    jpfamps said:

    Might be to conform with the regs re fuses blowing on transformer secondary shorts.
    Funnily enough another job this week was a nuisance failure on an Orange amp with a filament fuse... you can't win :).

    Although you can cheat - I'm sure you know what I mean ;).

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • HootsmonHootsmon Frets: 15924
    jpfamps said:
    ICBM said:
    Update on this - it was a polyswitch (thermistor) failure... they must have "improved" the model, unfortunately.

    Might be to conform with the regs re fuses blowing on transformer secondary shorts.


    It's Scotty and Kirk havin' a conversation about the ship

    PS Thanks John  :)
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