[TechAssist] Re: Diode testing
- From: walter wood <wwood_38478@xxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 27 Aug 2004 21:31:45 -0700 (PDT)
that is correct!!!
Walter
--- Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
wrote:
> For most meters, the reading on the diode test
> function is actually a
> voltage. That is, if you took a current limited
> power supply and applied a
> forward biased voltage to the diode, measuring it
> with another meter you
> should obtain the reading of a meter using a
> "diode" test. So a
> theoretically perfect silicon diode would measure
> about .6V, a germanium
> diode about .2V.
>
> 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: "Paul" <dntwntv@xxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, August 27, 2004 12:46 PM
> Subject: [TechAssist] Re: Diode testing
>
>
> > I don't know how you can read voltage on the
> diodes test function. But
> then I don't know all the meters and there
> capabilities. I have a fluke and
> a beckman and they both read about the same in
> this instance. I did notice
> that if put on the 200ohm scale that with one of
> these diodes, the reading
> will change like a charging capacitor in the
> negative direction. If that
> makes any sense. Here is the kicker. The new
> diode that just came in checks
> much like the old ones.I am really confused now.
> I am going to change them
> when I get both of them in. Supplier only had
> one.
> >
> Paul
> > Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
> wrote:
> > 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"
> > To:
> > 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 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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> > 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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