[time-nuts] HP5328A LEDS driver transistor

[Stan Searing]

A good source of replacement parts for test equipment is Sphere Research (
http://www.sphere.bc.ca/ ).
They don't show any in stock, but you could email.
NTE is a good source for replacement parts, but the NTE189 is really
expensive ($26.73 from Newark
and $30.59 from Mouser).  For the cost of a couple of these you can get a
whole 5328A (I have one or two
on my shelf I'd sell for $50 if you are ever up in San Jose).
I'd use a MJE171GOS-ND<http://search.digikey.com/us/en/products/MJE171G/MJE171GOS-ND/919498>
 or 497-4829-5-ND<http://search.digikey.com/us/en/products/2SB772/497-4829-5-ND/954133>
from
DigiKey (but as mentioned by others,
watch the pinout, as most any power tab transistor will have the collector
in the center,
while the MPS-U51 is one of the few exceptions).  You might also need to
slim down
the leads to fit the PC board.

Stan




On Sun, Jan 22, 2012 at 12:34 PM, Don Latham <djl at montana.com> wrote:

> 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
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> www.sixmilesystems.com
>
>
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