[TechAssist] Re: Diode testing
- From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 27 Aug 2004 16:58:24 -0500
This sounds like a Saturday project, and as luck would have it...
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: "Christopher Barnak" <cbarnak@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, August 27, 2004 2:24 PM
Subject: [TechAssist] Re: Diode testing
> 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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