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Martin Logan Summit - fuse blowing - ICEpower 200ASC (300ASC)

Discussion in 'd.i.y.' started by ChrisPa, Nov 3, 2017.

  1. ChrisPa

    ChrisPa pfm Member

    From my research so far this I think I'm going to struggle with this, so 'll grateful if anyone has suggestions...

    About 2 years ago (life's been busy...) I made one of ML Summits blow fuses after bu**#ring it up with a toaster, and I've just got round to diagnosing and and trying to fix it.

    The overall symptoms now are that it blows the fuse in the mains cable as soon as you turn the mains on.

    Having at last got round to opening the back, it contains a stack of 3 circuit boards - active crossover board for the bass drivers and 2x icepower. Each Summit has 2 bass drivers - one firing forwards and one downwards. Each is driven by its own ICEpower 200ASC. The mains only goes into the 2 Icepowers. The icepowers also provide a low voltage power supply output, and these are used to provide power to the active crossover board and thus the rest of the speaker.

    I haven't yet confirmed that one (or both) of the icepowers is (are) faulty, but it's certainly pointing that way.

    So my problem is getting hold of replacement 200ASC or 300ASC - the 300ASC is a more powerful pin-compatible replacement. They seemed to be comparatively readily available this time last year - IIRC, that was the time Fox threw together some power amps using the 300ASC modules. But there doesn't seem to be anything about now. I know I've just missed an 200ASC on ebay from Germany - it was available when I searched earlier this week but is now "out of stock"

    So whilst I carry on with the diagnosis, I need to find a replacement module.

    If it's the only way of getting hold of a module, then I think I'd be quite happy with someone handling this as a repair (IE I pay someone to fix it instead of DIY) if they can source the amp module, as long as it's not at an extortionate price.

    Thoughts, ideas, suggestions all welcome.


    (For those of you interested in how a toaster can blow an amplifier..

    The toaster we had at the time had decided it was reaching end of life, and wouldn't always latch down (a little electromagnet holds the toaster latched down, the timer circuit keeps the electromagnet in circuit and breaks the circuit when it's decided the toast has had enough) and it could be persuaded to latch if you repeatedly and rapidly pushed the toast down using the normal handle. One one occasion: after a few pumps on the handle, the new house wiring - now with circuit breakers and RCDs instead of the old fuse box - tripped. Unfortunately, the repeated cycling and rapid breaking of current through the toaster's heater element (coil) is akin to using a coil within a car to generate a spark (high voltage) from a 12V supply. IE. I successfully used the toaster to generate a voltage spike on the mains) :( :rolleyes:
  2. misterdog

    misterdog Not the canine kind

  3. JohnW

    JohnW Trade: Lakewest


    If you don't get anywhere I can take a look at the amps for your - especially if ones still working I can use the working amp as a reference for the blown unit...

    For Switching PSU's I use a device called a Huntron Tracker to test semiconductor junctions etc. why having a second working unit eases the debugging.
  4. Barrymagrec

    Barrymagrec pfm Member

    I used to play with one of those - quite handy at times, but it packed up and the owner wouldn`t fork out for the fix.
  5. Arkless Electronics

    Arkless Electronics Trade: Arkless

    I use the 5R output of a valve Advance signal generator, with a variety of other R's available manually, with a scope across its output to do the same job...
  6. hifinutt

    hifinutt hifinutt

    wow , thanks for warning on toaster !! never knew that could happen and hope you get those wonderful summit fiixed
  7. Arkless Electronics

    Arkless Electronics Trade: Arkless

    It can't. Don't worry.
  8. ChrisPa

    ChrisPa pfm Member

    It did :)
    On 3 separate occasions
    On each occasion it tripped the circuit breaker and RCD
    On a previous occasion it took out a Hypex NC400 PSU
    On the last occasion (before its replacement) it took out the ML

    Now it may have been the toaster having an effect on other equipment on the circuit or some strange aspect of loading/connection of that circuit that then took out the ML.
    But it was decidedly the toaster
  9. ChrisPa

    ChrisPa pfm Member

    Responses are much appreciated.


    Thanks, I'd found those, but interestingly there is no visual sign of any blown components on my Icepowers.

    This link potentially seems most relevant, although it refers to a 250 rather than a 200/300
    "My guess is that at least one of the primary switching MOSFETs was damaged (short circuited drain to source) possibly by a voltage surge."

    And there seems to be a nominal schematic available here


    Thanks for the offer - much appreciated. I'll see how I progress initially - you are a busy man and I wouldn't want to divert you unnecessarily
  10. Arkless Electronics

    Arkless Electronics Trade: Arkless

    Nope. You may have had some issue with how your amp responds to brown outs (probably cross-conductance issues in a class D amp) but there is no chance of major voltage spikes from a toaster. It's a small air cored inductance and wound from resistance wire such as nichrome which would render the Q of the circuit as nowt worth reporting. Toaster not guilty. how your equipment responds to sudden drops of 20-50V on the mains for a fraction of a second would be more worthwhile as a possible modus operandi here...
  11. JohnW

    JohnW Trade: Lakewest


    It would take me no more then an hour to repair so really no problem (at least find the blown parts) - sometimes its good to take a break from a long project - clears the cobweb's from the mind..
  12. hifinutt

    hifinutt hifinutt

    now thats reassuring to know , when i had my glorious summit x i often wondered where i would go if they went wrong
  13. Dark Energy

    Dark Energy pfm Member

    Strange to think of an electrostatic speaker powered by a Class D amplifier with an electrolytic capacitor in the signal path.
  14. JemHayward

    JemHayward pfm Member

    The IcePower modules power the bass drivers only, and the crossover frequency is quite low, so your main amplifier drives the panel, via a passive crossover, and then the bass is filtered at line level, and re-amplified. I've always been slightly uncomfortable about the arrangement, but I works really well, making the speakers easy to drive with a relatively modest amplifier. I've used Naim NAP250 (struggled with the HF impedance and prone to shutting down), a lovely EAR890 and currently using Hypex UcD modules, which sound superb, and are only about 25W but will drive the speakers louder than I can cope with...

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