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Audio Power Transistors - Buying in Bulk

dank123

Hi All,

Does anyone have a solid opinion on the quality of Multicomp Pro MJ15003 and MJ15004 power transistors (Newark# 76AH5818 and 76AH5819)? I want to stock up on these parts as I use them quite a bit and the Multicomp Pro ones come in at about half the cost of the other name brand devices. I use these parts for vintage audio amplifier repair and the occassional amp build from scratch. Not exactly critical applications, but I'd like to get some assurance that they are at least worth the money. Otherwise, I may as well just spend the extra and get ONSEMI. Has anyone tested this Multicomp Pro transistors to see what conditions they fail under as compared to the ONSEMI ones? 

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    Looking at the data sheets for the parts I would sy that there are definite causes for concern:

    The features section of the Multicomp data sheet seems to be for a different part.

    Multicomp features from data sheet.

    image

    The gain is wrong, the specified current range is wrong, what does "diode protection' even mean ?, there is no base emitter resistor in the Motorola/On Semi parts.

    The figure for Hfe is specified more reasonably in the data section fo the data sheet:

    image

    There is, as Shabaz has pointed out very little information in the Multicomp data sheet (most of the graphs on the Onsemi data sheet are omitted).

    So if the data sheet is both brief and self-inconsistent you have very little idea of what you are buying.

    On the way home last night I was thinking about the set up needed to test these parts for performance over a reasonable working range ( maybe not needing to go as far as the full specified rang).

    You would need a dual channel SMU or equivalent, capable of 10A (@ 2V) and 140V(@1A-pulsed), and most difficult, 5A at 50V

    Some way of measuring the thermal resistance - this is challenging - you need to put serious power into the device. keep the case temperature constant and measure the chip temperature.

    I guessed it would take a couple of weeks work to set up a rig to do this (non automated and over a limited number of set points) using a suitable lab power supply and standard electronic components with some kind of low power pulse generator and a scope. Or you could just buy the proper gear but expect no change from £50k.

    Is this a good use of time ?

    I would think that it isn't because the parts are not well enough specified to be sure that you would be getting a consistent product, regardless of the economics.

    The real thing from Mouser cost £4.53 if you buy 100, the Multicomp part is £3.26 - so you save £1.27 on each one and as Shabaz says, almost all your customers would rather have the Onsemi parts.

    MK

  • 0 in reply to michaelkellett
    michaelkellett said:
    almost all your customers would rather have the Onsemi parts.

    "No one gets fired for buying IBM" was the IT equivalent for that.

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