sci.electronics.repair - 25 new messages in 9 topics - digest

sci.electronics.repair
http://groups.google.com/group/sci.electronics.repair?hl=en

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Today's topics:

==============================================================================
TOPIC: Fuse: fast blown vs slow blown
http://groups.google.com/group/sci.electronics.repair/t/075c97d6b6b6e1f0?hl=en
==============================================================================

== 1 of 5 ==
Date: Tues, May 31 2011 11:47 am
From: Jamie

Jeff Liebermann wrote:

> On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott <tim@seemywebsite.com>
> wrote:
>
>
>>On 05/31/2011 08:57 AM, Man-wai Chang wrote:
>>
>>>>Your best bet is to get the right fuse, and at least try to fix the
>>>>fault before you turn the equipment on with your shiny new fuse.
>>>
>>>For a multimeter, is it always better to use a fast blow fuse?
>
>
>>Check to make sure that the fuse isn't being used as the current shunt
>>-- if it is, then you don't just need the right current rating, you need
>>a matched fuse.
>
>
> Chuckle. If a fuse were used as a current shunt, then when the fuse
> blows, instead of a few millivolts across the fuse, the meter now gets
> the full voltage of whatever is being measured. The fuse holder
> contact resistance will probably be larger than the wire resistance in
> the fuse (fast blow). I don't think anyone uses a fuse as a current
> shunt.
>
Hush, you wasn't suppose to notice that! Built in obsolescence.

Jamie

== 2 of 5 ==
Date: Tues, May 31 2011 12:18 pm
From: "Michael A. Terrell"

Jeff Liebermann wrote:
>
> On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott <tim@seemywebsite.com>
> wrote:
>
> >On 05/31/2011 08:57 AM, Man-wai Chang wrote:
> >>> Your best bet is to get the right fuse, and at least try to fix the
> >>> fault before you turn the equipment on with your shiny new fuse.
> >>
> >> For a multimeter, is it always better to use a fast blow fuse?
>
> >Check to make sure that the fuse isn't being used as the current shunt
> >-- if it is, then you don't just need the right current rating, you need
> >a matched fuse.
>
> Chuckle. If a fuse were used as a current shunt, then when the fuse
> blows, instead of a few millivolts across the fuse, the meter now gets
> the full voltage of whatever is being measured. The fuse holder
> contact resistance will probably be larger than the wire resistance in
> the fuse (fast blow). I don't think anyone uses a fuse as a current
> shunt.

Too hard to calibrate. :)

I used some test fixtures on the PRC-77 QA line for module
interchangability that had to be returned to the cal lab if a module
blew a fuse. !@#$%^&*( RCA/NATO design. @#$%^&*

--
It's easy to think outside the box, when you have a cutting torch.

== 3 of 5 ==
Date: Tues, May 31 2011 12:38 pm
From: John Robertson

Man-wai Chang wrote:
>
> How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
> slow-brown one?
>

Hope this helps answer your question!

http://flippers.com/fuses.html

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

== 4 of 5 ==
Date: Tues, May 31 2011 2:41 pm
From: Baron

Man-wai Chang Inscribed thus:

>> It has 18 volts instead of 12 volts, but it uses the same diameter
>> coaxial connector. A fast fuse protects in 400 microseconds, but the
>> slow blow does not blow that fast so the 45 nanometer digital device
>> gets melted in 1000 microseconds.
>
> Is the 13A BS1362 fuse a fast blow one?

No !

--
Best Regards:
Baron.

== 5 of 5 ==
Date: Tues, May 31 2011 6:26 pm
From: "Phil Allison"

"Jeff Liebermann"

>>
>>Is the 13A BS1362 fuse a fast blow one?
>
> That's the number of the plug, not the fuse:

** Funny, I have any number of fuses in my bins with "BS 1362" printed on
them.

> <http://en.wikipedia.org/wiki/BS_1363>
>
> It does have a fuse inside, but I don't know the value or type.

**From the very same Wiki:

http://en.wikipedia.org/wiki/BS_1363#Fuses

A 13A, BS 1362 fuse is very much a Slow Blow !

.... Phil

==============================================================================
TOPIC: NiMH new battery conditioning
http://groups.google.com/group/sci.electronics.repair/t/642feb09361f607e?hl=en
==============================================================================

== 1 of 7 ==
Date: Tues, May 31 2011 11:27 am
From: dplatt@radagast.org (Dave Platt)

In article <3kt8u69j7d6i3cetop4hgcjfsv92ek2s8r@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

>True for the Duracell, which recommends 205ma for 15 hrs to recharge
>printed on the cell. The Energizer Recharge battery doesn't specify a
>charge current:
><http://data.energizer.com/PDFs/nh15-2000.pdf>
>However, the recommended battery charger is a quick charger:
><http://data.energizer.com/PDFs/ch15mn2.pdf>
>with a 15 minute charge time.
>
>I've been testing batteries since about 2005 while working on a
>product that I won't discuss. However, I will point out that many
>NiCd batteries can be quick charged at ridiculously high rates, as
>long as certain (unspecified) conditions are met. If you don't mind,
>I'll leave this unsubstantiated.
>
>Incidentally, the Sanyo ENELOOP battery data sheet recommends fast
>charging at 2A for 1.1 hrs:
><http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf>

Interesting. Another page in the Sanyo FAQ section (at
http://us.sanyo.com/eneloop/FAQs) says:

Though it is possible to charge an eneloop battery in a "Quick
Charger", it is not recommended. We recommend charging eneloop
batteries in a NiMh charger that is 2 hours or more. Charging eneloop
batteries in a "Quick Charger" can reduce the overall life of the
battery.

I've read statements to the effect that one reason you would want to
use moderately-fast charging rates (e.g. 1C) rather than the low rates
traditional for most NiCd cells (e.g. 0.1C), is that the NiMH cells
will heat up more abruptly when they reach full charge, and the
charging power starts turning into heat rather than electrochemical
potential. The abrupt rise in cell temperature is easier to detect
reliably (via a temperature sensor and/or due to the zero-delta-V
effect) than if you were charging more slowly... and thus a more
reliable "full charge, stop now!" shutoff circuit can be designed, and
avoid overcharging (which I understand NiMH cells don't tolerate at
all well).

>Incidentally, all of the marine radios I helped design were required
>to function down to 10.0VDC applied power. They couldn't reach rated
>TX power at 70% of rated voltage, but still had to belch at least a
>few watts of RF and remain functional.

A good decision! It bothers me that a lot of HF and VHF radios "poop
out" at much below 12 volts.

>I'm rather mystified by the results. Although the improvement in
>capacity after 3 charge-discharge cycles is minor (10-15%), it still
>seems for real. My previous tests didn't show such an increase in
>capacity. Instead, it showed a deterioration in capacity. However, I
>was testing for something quite different, and was working with a mix
>of old and new cells.

For what it's worth, the Sanyo FAQ page cited above does make
reference to the break-in effect:

Should I store my batteries charged or uncharged?

If stored with charge, it is possible that when you return to use
the battery there may still be some charge left in the battery,
therefore it will enable you to use it right then and there. Also,
by keeping some charge in the battery, it will require you to
"cycle" the battery fewer times until it reaches its peak charge.
If you store them with no charge, you will have to "cycle" the
battery multiple times until it reaches its peak charge.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

== 2 of 7 ==
Date: Tues, May 31 2011 12:54 pm
From: "William Sommerwerck"

> Though it is possible to charge an eneloop battery in a
> "Quick Charger", it is not recommended. We recommend
> charging eneloop batteries in a NiMh charger that is [sic]
> 2 hours or more. Charging eneloop batteries in a "Quick
> Charger" can reduce the overall life of the battery.

A two-hour charge is, by any reasonable standard, a "quick charge". It would
be at least 0.5C -- hardly a slow charge.

== 3 of 7 ==
Date: Tues, May 31 2011 6:46 pm
From: "Phil Allison"

"William Sommerwanker"
>>
>> Though it is possible to charge an eneloop battery in a
>> "Quick Charger", it is not recommended. We recommend
>> charging eneloop batteries in a NiMh charger that is [sic]
>> 2 hours or more. Charging eneloop batteries in a "Quick
>> Charger" can reduce the overall life of the battery.
>
> A two-hour charge is, by any reasonable standard, a "quick charge". It
> would
> be at least 0.5C -- hardly a slow charge.
>

** Standard charge for a NiMH is 16 hours at 0.1C.

Quick chargers deliver about 0.2C to 0.5 C

Fast chargers deliver 1C to 4C ( ouch ! )

Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity - the same
charger has multiple rates.

So called " simple " chargers have a timer as the only cut out.

A 4C fast charger that only has a timer is a lethal weapon.

IME - the worst offenders in supplying chargers that are practically
guaranteed to ruin the cells are the battery makers - ie Energiser, Varta
and Sanyo.

Funny about that.

.... Phil

== 4 of 7 ==
Date: Tues, May 31 2011 7:11 pm
From: "William Sommerwerck"

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94ljveFq68U1@mid.individual.net...

> "William Sommerwanker"

I thought you'd reformed. But you haven't. Why don't you just go back to
being a foul-mouthed jerk? That's what you want, isn't it? You want people
to hate you, because it makes you feel superior.

The worst part is that when you aren't making nasty remarks, you almost
always have somthing worth hearing.

Our own little Eric Cartman. How charming.

>>> Though it is possible to charge an eneloop battery in a
>>> "Quick Charger", it is not recommended. We recommend
>>> charging eneloop batteries in a NiMh charger that is [sic]
>>> 2 hours or more. Charging eneloop batteries in a "Quick
>>> Charger" can reduce the overall life of the battery.

>> A two-hour charge is, by any reasonable standard, a "quick charge".
>> It would be at least 0.5C -- hardly a slow charge.

> ** Standard charge for a NiMH is 16 hours at 0.1C.
> Quick chargers deliver about 0.2C to 0.5 C
> Fast chargers deliver 1C to 4C (ouch!)
> Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity --
> the same charger has multiple rates.

> So-called "simple" chargers have a timer as the only cutout.
> A 4C fast charger that only has a timer is a lethal weapon.

> IME -- the worst offenders in supplying chargers that are practically
> guaranteed to ruin the cells are the battery makers -- ie Energizer,
> Varta, and Sanyo.
> Funny about that.

As they sell batteries, why should it be funny?

Based on my experience at Microsoft Hardware, and MAHA's documentation, 0.1C
is not considered an appropriate charge rate for NiMH cells. Higher rates
are recommended, supposedly because they pump more charge into the cell
before the cutoff voltage or temperature is reached.

I rarely charge faster than 0.3C. That's just basic cowardice on my part.

== 5 of 7 ==
Date: Tues, May 31 2011 7:35 pm
From: "Phil Allison"

"William Sommerwanker = Colossal FUCKWIT "
>
>>> A two-hour charge is, by any reasonable standard, a "quick charge".
>>> It would be at least 0.5C -- hardly a slow charge.
>
>> ** Standard charge for a NiMH is 16 hours at 0.1C.
>> Quick chargers deliver about 0.2C to 0.5 C
>> Fast chargers deliver 1C to 4C (ouch!)
>> Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity --
>> the same charger has multiple rates.
>
>> So-called "simple" chargers have a timer as the only cutout.
>> A 4C fast charger that only has a timer is a lethal weapon.
>
>> IME -- the worst offenders in supplying chargers that are practically
>> guaranteed to ruin the cells are the battery makers -- ie Energizer,
>> Varta, and Sanyo.
>> Funny about that.
>
> As they sell batteries, why should it be funny?

** FFS - the irony is pretty damn strong.

Not to mention being contrary to consumer law.

> Based on my experience at Microsoft Hardware, and MAHA's documentation,
> 0.1C
> is not considered an appropriate charge rate for NiMH cells.

** Totally IRRELEVANT.

For * loose cells * sold to the public and in the absence of " smart "
chargers that treat each cell as in individual - it is the only reliably
safe method.

> Higher rates
> are recommended, supposedly because they pump more charge into the cell
> before the cutoff voltage or temperature is reached.

** Requires a smart charger, matched packs of cells et alia ad nauseam.

A whole different ball game.

> I rarely charge faster than 0.3C.

** Still well capable of ruining NiMH cells left on charge for too long.

BTW:

Ruining refers to a simultaneous loss of capacity and LARGE increases in
self discharge rate and internal resistance.

.... Phil

== 6 of 7 ==
Date: Tues, May 31 2011 8:21 pm
From: "William Sommerwerck"

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94lmqvFcfeU1@mid.individual.net...

>> Higher rates
>> are recommended, supposedly because they pump more charge
>> into the cell before the cutoff voltage or temperature is reached.

> ** Requires a smart charger, matched packs of cells et alia ad nauseam.
> A whole different ball game.

Not for me. I own two smart chargers.

>> I rarely charge faster than 0.3C.

> ** Still well capable of ruining NiMH cells left on charge for too long.

See preceding.

== 7 of 7 ==
Date: Tues, May 31 2011 8:24 pm
From: "Phil Allison"

"William Sommerwanker = Context Shifter and LIAR "

** DROP FUCKING DEAD

==============================================================================
TOPIC: Is there a fuse on a Samsung SV4000?
http://groups.google.com/group/sci.electronics.repair/t/d375f8c622c671d0?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, May 31 2011 12:19 pm
From: PlainBill@yawhoo.com

On Tue, 31 May 2011 10:16:29 -0700 (PDT), myfathersson
<licensedtoquill@gmail.com> wrote:

>Sorry, let me re-phrase that: DOWNLOADING NOW means you have to click
>on some virtually hidden link two thirds down on the page to download
>
>Doing that downloads something called a .djvu file. which requires
>installing Nuance Software .pdf reader.
>
>When you do that, it just tells you that it cant open the mysterious
>286kb sv4000w.djvu file you have just downloaded!
That's why intelligent people avoid places like eserviceinfo and the
dozens of sites that give bogus hits on Google.

Instead, go to Elektrotanya. The site is in Poland, the menus are in
both Polish and English. The site sometimes is flaky; as a registered
user (registration is free) I have not had problems downloading when
using a decent browser (FoxFire). For those who are offended by
Polish menues, registration, or Foxfire, I can only say C'est la vie!

http://elektrotanya.com/?q=showresult&megnev=samsung&megnev2=sv-4000&kategoria=&kat2=all

PlainBill

== 2 of 2 ==
Date: Tues, May 31 2011 12:45 pm
From: "Michael A. Terrell"

myfathersson wrote:
>
> Sorry, let me re-phrase that: DOWNLOADING NOW means you have to click
> on some virtually hidden link two thirds down on the page to download
>
> Doing that downloads something called a .djvu file. which requires
> installing Nuance Software .pdf reader.
>
> When you do that, it just tells you that it cant open the mysterious
> 286kb sv4000w.djvu file you have just downloaded!

That's because it's not a .PDF file. You need a DJVU viewer:

http://windjview.sourceforge.net/

--
It's easy to think outside the box, when you have a cutting torch.

==============================================================================
TOPIC: microwave oven stopping prematurely, repairable?
http://groups.google.com/group/sci.electronics.repair/t/a4366967d76451a5?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, May 31 2011 1:21 pm
From: Cydrome Leader

whit3rd <whit3rd@gmail.com> wrote:
> If you're OK with tools, and can discharge the capacitor
> safely, consider disassembling the oven and cleaning it.
>
> An insect getting carbonized in the HV section could be
> the only problem here, and you gotta scrub the carbon track
> away to fix that.

==============================================================================
TOPIC: Introduction of PIC in my School
http://groups.google.com/group/sci.electronics.repair/t/fecb73ca77e41f85?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, May 31 2011 2:56 pm
From: "fynnashba@yahoo.com"

Hi friends and good pals out there,
I want to introduce Micro-controllers in my schools electronics
curriculum as it is fast replacing traditional electronics. I need
very good books, Lab equipment and may be a course outline on PICs for
my students. Where do I get all these?
THANKS.

== 2 of 2 ==
Date: Tues, May 31 2011 4:19 pm
From: Jamie

fynnashba@yahoo.com wrote:

> Hi friends and good pals out there,
> I want to introduce Micro-controllers in my schools electronics
> curriculum as it is fast replacing traditional electronics. I need
> very good books, Lab equipment and may be a course outline on PICs for
> my students. Where do I get all these?
> THANKS.
http://www.microchip.com/

==============================================================================
TOPIC: Power transistor question...
http://groups.google.com/group/sci.electronics.repair/t/48e3a91c572ef00c?hl=en
==============================================================================

== 1 of 4 ==
Date: Tues, May 31 2011 3:34 pm
From: Jamie

Dave wrote:

> "Phil Allison" <phil_a@tpg.com.au> wrote in message
> news:94j1ebFms1U1@mid.individual.net...
>
>>"Meat Plow"
>>
>>
>>>>http://www.youtube.com/watch?v=zEA5MfllPdg
>>>
>>>Not a bad little meter for the $$$$. Anyone who does work on consumer
>>>electronics ought to have one or something similar. Removes a lot of
>>>guess work.
>>
>>
>>** I disagree.
>>
>>An LCR meter is more useful for design and production than in servicing.
>>
>>Many low cost DMMs include capacitance ranges that can measure from a few
>>pF up to 200 or 2000uF.
>>
>>A dedicated ESR meter handles electros just fine while in circuit - and
>>lets you test all kinds of cells too, which an LCR meter often cannot.
>>
>>Any DMM can read the resistance of an inductor or transformer winding.
>>
>>The only function left is to measure inductors for value.
>>
>>
>>.... Phil
>>
>
>
> Wanted to thank *everyone* for the info and encouragement I have received in
> this discussion. Bottom line for me, at least for now, is simply don't test
> in-circuit (pop one lead and then test after discharging). Have also found
> a ton of material on youtube and the net that convinces me to get a
> dedicated ESR meter (or possibly build one.) Anyway, thanks all for a very
> enlightening discussion.
>
> Take it easy...
>
> Dave
>
>
I use a cheap B&K LCR, it does in circuit beautifully.

Jamie

== 2 of 4 ==
Date: Tues, May 31 2011 3:51 pm
From: Meat Plow

On Tue, 31 May 2011 12:17:38 +1000, Phil Allison wrote:

> "Meat Plow"
>
>>> http://www.youtube.com/watch?v=zEA5MfllPdg
>>
>> Not a bad little meter for the $$$$. Anyone who does work on consumer
>> electronics ought to have one or something similar. Removes a lot of
>> guess work.
>
>
> ** I disagree.
>
> An LCR meter is more useful for design and production than in servicing.
>
> Many low cost DMMs include capacitance ranges that can measure from a
> few pF up to 200 or 2000uF.
>
> A dedicated ESR meter handles electros just fine while in circuit - and
> lets you test all kinds of cells too, which an LCR meter often cannot.
>
> Any DMM can read the resistance of an inductor or transformer winding.
>
> The only function left is to measure inductors for value.
>
>
> .... Phil

I'd like to see the meter described test at a higher frequency but other
than that I can't find much else wrong. I've been relying on an old Tenma
cap meter for years. It's gets you in the ball park. And there were
reliable repairs before LCR and ESR meters. I know, been at it from high
school back in 1970. These days I tend to shy away from anything I need
an ESR meter for. Plenty of vintage stuff out there that people like to
keep going.

--
Live Fast Die Young, Leave A Pretty Corpse

== 3 of 4 ==
Date: Tues, May 31 2011 6:34 pm
From: "Phil Allison"

"Meat Plow"
>
> I'd like to see the meter described test at a higher frequency but other
> than that I can't find much else wrong. I've been relying on an old Tenma
> cap meter for years. It's gets you in the ball park. And there were
> reliable repairs before LCR and ESR meters. I know, been at it from high
> school back in 1970. These days I tend to shy away from anything I need
> an ESR meter for. Plenty of vintage stuff out there that people like to
> keep going.

** ESR meters are MOST useful with older equipment, particularly valve
amplifiers.

All those electros are old and have been running in a hot environment.

..... Phil

== 4 of 4 ==
Date: Tues, May 31 2011 8:32 pm
From: "Dave"

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:QVdFp.9148$rq2.7889@newsfe12.iad...
> Dave wrote:
>
>> "Phil Allison" <phil_a@tpg.com.au> wrote in message
>> news:94j1ebFms1U1@mid.individual.net...
>>
>>>"Meat Plow"
>>>
>>>
>>>>>http://www.youtube.com/watch?v=zEA5MfllPdg
>>>>
>>>>Not a bad little meter for the $$$$. Anyone who does work on consumer
>>>>electronics ought to have one or something similar. Removes a lot of
>>>>guess work.
>>>
>>>
>>>** I disagree.
>>>
>>>An LCR meter is more useful for design and production than in servicing.
>>>
>>>Many low cost DMMs include capacitance ranges that can measure from a few
>>>pF up to 200 or 2000uF.
>>>
>>>A dedicated ESR meter handles electros just fine while in circuit - and
>>>lets you test all kinds of cells too, which an LCR meter often cannot.
>>>
>>>Any DMM can read the resistance of an inductor or transformer winding.
>>>
>>>The only function left is to measure inductors for value.
>>>
>>>
>>>.... Phil
>>>
>>
>>
>> Wanted to thank *everyone* for the info and encouragement I have received
>> in this discussion. Bottom line for me, at least for now, is simply
>> don't test in-circuit (pop one lead and then test after discharging).
>> Have also found a ton of material on youtube and the net that convinces
>> me to get a dedicated ESR meter (or possibly build one.) Anyway, thanks
>> all for a very enlightening discussion.
>>
>> Take it easy...
>>
>> Dave
>>
>>
> I use a cheap B&K LCR, it does in circuit beautifully.
>
> Jamie
>
>

Hey Jamie, thanks for the note. So, how do you perform an in-circuit ESR
test on a suspect cap? Do you bother to discharge it, or do you just let
the circuitry around the cap do that? And how reliable are the numbers you
come up with? I tried to do an in-circuit test today on a cap and thought I
had gotten lucky with my first shot. A 10uF @ 100V cap gave me an ESR
reading of 42.15 in-circuit, but when I popped it out and tested it again it
dropped to 0.12. big difference! Still trying to figure out what I might
have been doing wrong...

Have since discovered a different cap that may actually be the problem. A
.22uF @ 50V cap with an ESR reading of 25+ ohms. Am thinking this component
may be where the vertical hold sync pulse gets lost, as it feeds an
oscillator/mixer transistor which feeds the output transistor of the
vertical hold circuitry. All of this two days after I discovered I had an
ESR meter and didn't know it. <shaking head>

Dave

==============================================================================
TOPIC: Request transistor cross reference
http://groups.google.com/group/sci.electronics.repair/t/6d311b79499b89d6?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, May 31 2011 3:32 pm
From: jjb_at_northstate_dot_net@foo.com (kaplanB)

kaplanB had written this in response to
http://www.electrondepot.com/repair/Re-Request-transistor-cross-reference-126006-.htm
:
I reenter the discussion with a bit of trepidation as I'm am just a pastor
trying to fix his cooktop, not an
electrical engineer.

I have learned a LOT from your posts and this adventure. I think I have
learned enough to say that what
I'm trying to find a substitute for (Shindengen T30G40) is not an IGBT or
a NPN. It is a PNP! My thinking
is based on three main factors.

I've drawn my own schematic and the cooktop (Kenmore 564.4498512) seems to
look like a "quasi-
resonant" circuit I found when researching induction cooktop designs.
These designs use PNP
transistor.

Second, the voltage at the base, measured on a working element, is -56 Vdc
when idle and -60 Vdc
when energized. Doesn't' that "turn on" a PNP transistor?

Third, pulled the transistors off the board and one of the three power
transistors tests OK as a PNP.

When we all thought this was an NPN I had agreed with Dr. Ornitz's
assessment that an On Sem
MJW18020 would perhaps work as a substitute. Now, I'm looking for a PNP
version but having no luck
so far.

I'm thankful for all the "wise guys" who weigh in on this issue.

Kap B

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== 2 of 2 ==
Date: Tues, May 31 2011 4:14 pm
From: "Dave M"

kaplanB wrote:
> kaplanB had written this in response to
> http://www.electrondepot.com/repair/Re-Request-transistor-cross-reference-126006-.htm
>>
> I reenter the discussion with a bit of trepidation as I'm am just a
> pastor trying to fix his cooktop, not an
> electrical engineer.
>
> I have learned a LOT from your posts and this adventure. I think I
> have learned enough to say that what
> I'm trying to find a substitute for (Shindengen T30G40) is not an
> IGBT or a NPN. It is a PNP! My thinking
> is based on three main factors.
>
> I've drawn my own schematic and the cooktop (Kenmore 564.4498512)
> seems to look like a "quasi-
> resonant" circuit I found when researching induction cooktop designs.
> These designs use PNP transistor.
>
> Second, the voltage at the base, measured on a working element, is
> -56 Vdc when idle and -60 Vdc
> when energized. Doesn't' that "turn on" a PNP transistor?

Not necessarily... You have to measure the base voltage in respect to the
emitter. Assuming that it's a silicon device, you should see -0.65V
to -0.8V at the base with respect to the emitter. That will turn a PNP
transistor on. If the difference in voltage between base and emitter less
than 0.65V, then the transistor isn't on.

> Third, pulled the transistors off the board and one of the three power
> transistors tests OK as a PNP.

Questionable assumption... How do you know the others are PNP units? Do
they have the same part numbers?

>
> Kap B
>

Here's a quick spec on the T30G40 transistor:

Si NPN Power BJT
Shindengen Electric Mfg. Co., Ltd.
V(BR)CEO (V)=400
V(BR)CBO (V)=800
I(C) Abs.(A) Collector Current=30
Absolute Max. Power Diss. (W)=200
h(FE) Min. Static Current Gain=80
f(T) Min. (Hz) Transition Freq=7.0M
t(d) Max. (s) Delay time.=3.0u
t(s) Max. (s) Storage time.=3.0u
t(f) Max. (s) Fall time.=1.0u
Package=SIP
Military=N

That indicates that it's an NPN unit; not PNP. Are you sure that you're
testing the transistors correctly? Maybe you should post a quick narrative
on how you're trying to troubleshoot. And be careful that you know the
polarity of the test leads of the ohms function of your multimeter... A few
will fool you.

--
David
dgminala at mediacombb dot net

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http://groups.google.com/group/sci.electronics.repair/t/1ee83c788187e854?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, May 31 2011 5:50 pm
From: jialiu

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==============================================================================
TOPIC: zebra connector
http://groups.google.com/group/sci.electronics.repair/t/22ac512ae9f1d16c?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, May 31 2011 6:00 pm
From: "Shaun"

"Vale" wrote in message news:jK8Fp.29619$GZ3.6759@tornado.fastwebnet.it...

"Jeff Liebermann" <jeffl@cruzio.com> ha scritto nel messaggio
news:ev1au6l4fk6hevq9fvne7qhm8q5cp0qqrg@4ax.com...
> On Mon, 30 May 2011 17:43:17 +0200, "Vale" <vale@fastwebnet.it> wrote:
>
>>My expensive multimeter has got broken plastic pins that hold the lcd
>>disply
>>on the pcb.
>

Thanks all.I solved, hope for long time.
I've been luky, the dirt that was on the meter case display window was
perfectly corresponding to the dirt line on the display.
So I found the right position.
It has been not so easy to align the display on pcb, I supplied the meter
with a voltage, tried hundreds of positions until it displaied the rights
measurement.
I got help from a pair of chinese spring loaded clamps to firmly block the
display and put some drops of cyanoacrylate on corners.
Than used plenty of epoxy glue to make it stable.
The meter now works quite perfectly, only the last digit is incomplete, but
I'm happy anyway.
At least that experience has provided more knowledge to zebra gadgets.
Thanks everybody and....don't keep your meters too clean!

What brand is your meter? You can probably order parts for it if it is not
too old. When you do order parts, order new zebra strips aswell.

Shaun

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