[TechAssist] Re: measuring digital transistors
- From: Gary McCartney <number63@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 04 Jan 2002 10:33:41 -0500
What i usualy do is to get a new one out of my parts bins and compare
the resistances to the suspect device. If I don't have a new one in
stock, I can often find another transistor of the same number on the the
circuit board which I am repairing. I just pull it out and compare to
the suspect device. Then I might switch locations when I reinstal them,
and see if the unit acts the same or differently.
Gary McCartney
McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: number63@xxxxxxxxxxxxx
MYERSVCR@xxxxxxx wrote:
>
> Hello all
> I am a bit perplexed at how you measure a digital transistor. The one in
> question is
> a C144ES (or ECG2359 equiv) and there are lots of them on a Hitachi VCR board
> I am working on.
> This particular transistor pinout (from ECG catalog) has a base resistor of
> 47K and the old diode tests of the DMM are not working. I am getting around
> 94K ohms between 2 leads and I think I
> am measuring (2) 47K resistors in series within the transistor. Is this how
> you tell if they are good?
>
> The ECG catalog shows this as an SP92 case
> and pins as (1) ground (2) out (3) in NPN silicon
>
> The Hitachi schematic shows 0 volts on all three leads as a good reading and
> describes it as a load speed switch
> Hitachi VTM-141A VCR The transistor I was checking was Q753
> thanks, Craig
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