[time-nuts] HP5328A LEDS driver transistor

Don Latham djl at montana.com
Sun Jan 22 15:34:33 EST 2012


NTE lists their equivalent as: NTE-189 See:
http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search
Newark has 262 of them :-)
Don
Chris Albertson
> I have an eBay HP5328A counter with two dead digits on the display.  I
> figured out the problem was two dead transistors.  I can swap
> transistors with a good digit and the problem moves.
>
> I'd not worked on LED displays before.  Turns out only one digit is
> lit up at a time, they strobe the digits in sequence.  The dead
> transistor is the one that controls the all the anodes in the
> 7-segment LED module.  The service manual describes the transistor
> like this:  "part number = 1853-0326", "description = TRANSISTOR PNP
> SI ... FT-50MHZ"
> The p/n 1853-0326 cross references to a Motorola MPS-U51.  The MPS-U51
> data sheet matches the part that fails so I'm sure I got a correct
> cross ref.
> I took a photo of the dead transistor.  It is on .1" perf board for
> scale.   You can read the "3-326" p/n and see the Motorola "M" logo.
> http://www.dropbox.com/gallery/28915695/1/HP5328A?h=da35c1
>
> I look up the spec in the mps-u51 and see it is a to-220 like case and
> can handle 1W.  I'm really surprised it burned out as I doubt an LED
> requires 1W even if showing an "8".  Reading the mps-u51 spec sheet I
> see it has a low saturation voltage.  Maybe that is why the selected
> it as it is being driven by 7400 TTL logic that goes through a
> connector and has some resistors involved.
>
> Question:  These seem to be hardtop find.  Can anyone suggest a good
> sub"
>
>
>
> Thanks,
> Chris Albertson
> Redondo Beach, California
>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com






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