[TechAssist] Re: Diode testing
- From: "Christopher Barnak" <cbarnak@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 27 Aug 2004 15:24:06 -0400
Wayne,
Some diodes will generate a voltage when exposed to light. We use to
series several when I used to work GE to make a little solar array.
Current capacity was very low, but voltage was however much you got
when you series the diodes and then exposed them to a lamp, or to
the sun, which was the best. The diodes that did this were encased in a
sustance that light could penetrate. Usually gray, green, or clear bead
type.
Try it. The closer you get them to the bench lamp the more voltage they
generate.
Regards,
Christopher Barnak, CET
Norfolk Public Schools
School Plant Facilities
966 Bellmore Ave.
Norfolk, Va. 23504
Phone 757 628 3385
Fax 757 628 3392
cbarnak@xxxxxxxxxxxxx
>>> Wayne@xxxxxxxxxxxxxxxxxxxxx 8/27/2004 7:26:09 AM >>>
Wendsday I pull CR4401 pn 242907 from an RCA 169 chassis, and it
measured -1.2 volts on the diode check setting with a fluke 77 series
3.
Minus volts out of circuit on a
diode? What the heck? Changed the battery in the meter, same thing.
Changed the diode and the set worked.
How the heck do you get minus volts? That means that
there was some sort of capacitance/pn junction problem with that
diode.
Minus ohms.
Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, Fl. 32506-3310
Wayne@xxxxxxxxxxxxxxxxxxxxx
www.PensacolaTVRepair.Com
850-456-5995 voice
850-458-6369 fax
----- Original Message -----
From: "walter wood" <wwood_38478@xxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, August 26, 2004 9:24 PM
Subject: [TechAssist] Re: Diode testing
> It seems to depend on the meter, as to what the
> diode check position will read.
> I have a Micronta(inexpensive radio shack) that
> reads 820 t0 840 consistantly on good diodes.
> I have two Fluke meters, ond old (series 73) but
> great, and an expensive Model 83 series three.
> They both consistantly read 460 on the diode scale.
> I think you diodes are leaky.
> You have enough evidence that I would certainly
> replace them.
> Check the new ones out of circuit before installing
> them, and if weird make a note of it.
> There are some odd ball things out there.
> i've got a large spiral notebook full of such
> measurments.
> ALWAYS, use the same meter though, for comparaison,
> or note the results with the different ones.
> Another thing I like to do is take resistance
> measurements on key components, such as convergence
> ic's, regulators, outputs etc. on common products,
> on a set that is working correctly.
> I note this, and it helps more often than not.
> SAMS used to provide this.
> HTH
> Walter
> --- Paul <dntwntv@xxxxxxxxxxxxx> wrote:
>
> > When checking diodes for leakage, what range on
> > the ohm meter do you use and is there an
> > acceptable amount? Sounds like electronics 101
> > but I have a couple of diodes that are flat case
> > diodes mounted on a heat sink. They read 160
> > front to back on the diode check. No reading back
> > to front. However they read 20k on the ohms
> > scale. If heated this reading goes down to 2 or 3
> > K. I normally set my meter on 100k ohm for
> > leakage. I thought they must be leaking. But
> > wondered if there are some big diodes that test
> > this way normally? Someone said that 10X the back
> > to front was normal. These are in the secondary
> > of a SMPS + & -- 25v to convergence amps.
> >
> > Paul
> >
> > Paul ,B
> > Central TV&Video
> > 911W Grand Ave
> > Grover Beach Ca.
> > (805)481-8084
> >
> >
> >
>
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>
> =====
> Walter Wood
> Future Tech Home Center
> 2786 Hwy. 43 N.
> Lawrenceburg Tn. 38464
> 931-829-3337
> Fax 931-829-4044
> mailto:wwood_38478@xxxxxxxxx
>
>
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