sci.electronics.repair@googlegroups.com

Today's topics:

* Valves badged Orange , rebadged what make? - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/b405f7894dddeac4?hl=en
* microwave oven stopping prematurely, repairable? - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/a4366967d76451a5?hl=en
* Power transistor question... - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/48e3a91c572ef00c?hl=en
* WHOLESALE all BRAND(UGGBOOTS,SHOES,CLOTHES,HANDBAG,WATCH,JEANS,JERSEY,T-
SHIRT,SHIRTS,HOODY,EYEGLASS,CAP,SHAWL,WALLT) and so on. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/1ee83c788187e854?hl=en
* how to disassemble this AC Adapter? - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/79c2e64c02b38c5d?hl=en

==============================================================================
TOPIC: Valves badged Orange , rebadged what make?
http://groups.google.com/group/sci.electronics.repair/t/b405f7894dddeac4?hl=en
==============================================================================

== 1 of 2 ==
Date: Sun, May 29 2011 3:21 pm
From: "Gareth Magennis"

"Meat Plow" <mhywattt@yahoo.com> wrote in message
news:pan.2011.05.28.22.58.44@emutt.macspoofer.lmao...
> On Sat, 28 May 2011 14:33:30 +0100, Gareth Magennis wrote:
>
>> "Gareth Magennis" <sound.service@btconnect.com> wrote in message
>> news:mLWDp.24219$Am5.16040@newsfe05.ams2...
>>>
>>> . Best for my concern would be some NOS Mullards
>>>> or RCA.
>>>
>>>
>>>
>>> Yeah well, we could all say that.
>>> Doesn't help.
>>
>>
>> Sorry, that post reads a little curt, but for example:
>>
>> http://cgi.ebay.co.uk/EL34-CV1741-MULLARD-NOS-MATCHED-
> PAIR-/310210519111?
> pt=UK_Consumer_VintageAudio_RL&hash=item4839fce047Blimey.Gareth.
>
> I know a few that wouldn't bat an eyelash at that price.

You could experiment to see if any of them could really tell the difference
in a properly controlled double blind test.

I am highly suspicious of any opinions regarding "sound quality" obtained
otherwise.

Gareth.

== 2 of 2 ==
Date: Sun, May 29 2011 3:56 pm
From: Meat Plow

On Sun, 29 May 2011 23:21:24 +0100, Gareth Magennis wrote:

> "Meat Plow" <mhywattt@yahoo.com> wrote in message
> news:pan.2011.05.28.22.58.44@emutt.macspoofer.lmao...
>> On Sat, 28 May 2011 14:33:30 +0100, Gareth Magennis wrote:
>>
>>> "Gareth Magennis" <sound.service@btconnect.com> wrote in message
>>> news:mLWDp.24219$Am5.16040@newsfe05.ams2...
>>>>
>>>> . Best for my concern would be some NOS Mullards
>>>>> or RCA.
>>>>
>>>>
>>>>
>>>> Yeah well, we could all say that.
>>>> Doesn't help.
>>>
>>>
>>> Sorry, that post reads a little curt, but for example:
>>>
>>> http://cgi.ebay.co.uk/EL34-CV1741-MULLARD-NOS-MATCHED-
>> PAIR-/310210519111?
>> pt=UK_Consumer_VintageAudio_RL&hash=item4839fce047Blimey.Gareth.
>>
>> I know a few that wouldn't bat an eyelash at that price.
>
>
>
> You could experiment to see if any of them could really tell the
> difference in a properly controlled double blind test.
>
> I am highly suspicious of any opinions regarding "sound quality"
> obtained otherwise.
>
>
> Gareth.

You left out durability factor.

--
Live Fast Die Young, Leave A Pretty Corpse

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

== 1 of 3 ==
Date: Sun, May 29 2011 3:31 pm
From: Robert Macy

On May 28, 9:17 pm, tin6150 <tin6...@gmail.com> wrote:
> Hello folks, happy Memorial Day weekend to you all!
>
> My microwave is acting erratic, maybe you can help me see if it is
> repairable?  It can heat water, but tends to shut downs prematurely.
>
> I have read this repair faqhttp://www.repairfaq.org/sam/micfaq.htm#micsaf
> but didn't find answer to my problem.
>
> One evening I was cooking a frozen dinner, a chicken pot pie with a
> mesh for browning at the top of the paper container.  It is said to be
> microwave safe.  I followed instructions exactly.  But maybe 3 minutes
> into the nuking, there were a few spark, so I pulled the power cord as
> quickly as I could.  There were some burn smell, which lingered even
> after a week of non-use.  The microwave oven was clean, no spill over
> or splatter when I started nuking the pot pie.  I did not leave a fork
> in there either.
>
> The microwave in question is a panasonic inverter system, 1200 W.
> manufacture date is 2002.
>
> Currently, all electronics seems to work fine, touch pad works, clock
> runs, timer works.  no visible damage.  No paint problem from the
> spark.  I tried to heat a cup of water for 35 seconds, and microwave
> just shut off automatically after some 15-20 seconds (but clock panel
> still running, so the electronics seems to have shut something down.
> No error indicator of any sort that I can see).
>
> If I set power to 50%, then it will heat the water for 50 seconds to
> completion.  water temperature is very warm to the touch.  If I set
> power to 10%, then it will heat for more than 70 seconds to
> completion.
>
> Maybe eventually at more than 50 seconds even at the 50% power, it
> might shut off automatically when something gets too hot?  I am not
> sure if I want to try it if microwave isn't really going to be fully
> functional anyway.
>
> It is likely cheaper to just buy a new one, but as an
> environmentalist, I just hate to waste appliance that can otherwise
> work :)
>
> Much thanks in advance for any advices.
> Tin

Sounds slightly similar. Had a GE unit that started making an
internal arc sound [the arc burnt around the waveguide entrance to the
microwave chamber out of sight. Without total disassembly could not
see it].

Symptom sounds similar, uWave would run, then [in my case] hear arcing
sounds, and then shutdown. Arcing did NOT occur if a glass of water
were present. But arcing occurred if I was trying to toast something
dry, like bread. My guess was that the damped microwave chamber keeps
the voltage down enough there is no arcing. And when the chamber is
unloaded, the resonant voltages get high enough to enccourage the
arcing. Culmination of this was that after 'limping' along for 4
months, the burn spots in the waveguide feed required replacing the
unit, had to buy a new one.

== 2 of 3 ==
Date: Sun, May 29 2011 6:28 pm
From: whit3rd

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.

== 3 of 3 ==
Date: Sun, May 29 2011 10:32 pm
From: TonyS

On 29/05/2011 12:17 PM, tin6150 wrote:
>
> Hello folks, happy Memorial Day weekend to you all!
>
> My microwave is acting erratic, maybe you can help me see if it is
> repairable? It can heat water, but tends to shut downs prematurely.
>
> I have read this repair faq
> http://www.repairfaq.org/sam/micfaq.htm#micsaf
> but didn't find answer to my problem.
>
> One evening I was cooking a frozen dinner, a chicken pot pie with a
> mesh for browning at the top of the paper container. It is said to be
> microwave safe. I followed instructions exactly. But maybe 3 minutes
> into the nuking, there were a few spark, so I pulled the power cord as
> quickly as I could. There were some burn smell, which lingered even
> after a week of non-use. The microwave oven was clean, no spill over
> or splatter when I started nuking the pot pie. I did not leave a fork
> in there either.
>
> The microwave in question is a panasonic inverter system, 1200 W.
> manufacture date is 2002.
>
> Currently, all electronics seems to work fine, touch pad works, clock
> runs, timer works. no visible damage. No paint problem from the
> spark. I tried to heat a cup of water for 35 seconds, and microwave
> just shut off automatically after some 15-20 seconds (but clock panel
> still running, so the electronics seems to have shut something down.
> No error indicator of any sort that I can see).
>
> If I set power to 50%, then it will heat the water for 50 seconds to
> completion. water temperature is very warm to the touch. If I set
> power to 10%, then it will heat for more than 70 seconds to
> completion.
>
> Maybe eventually at more than 50 seconds even at the 50% power, it
> might shut off automatically when something gets too hot? I am not
> sure if I want to try it if microwave isn't really going to be fully
> functional anyway.
>
> It is likely cheaper to just buy a new one, but as an
> environmentalist, I just hate to waste appliance that can otherwise
> work :)
>
>
> Much thanks in advance for any advices.
> Tin

I have an older MW oven that wouldn't shut down for any irregularity.
One day it started sparking and had a smell, just like you said.
Upon closer investigation I found that the mica plate in front of the
wave guide had deteriorated and had a dark spot that arced under power.

I took the mica off and ran the device, and it worked just fine.
I ordered a sheet of mica on ebay to cut to size cause I couldn't get
the original. Before that arrived I found a MW Oven on the road side for
verge collection and removed the mica from there. I trimmed it a little
and fitted it in my oven. No problems ever since. Got a spare one now in
the junk box:)

Looks like the mica sheets can get damaged and take up moisture, which
sort of shorts out the micro wave energy.
Don't know if this happened to your machine but it wouldn't hurt to check.

Tony

Excerpt from the faq:
More on the waveguide cover and cleaning
That cover is made of an insulator transparent to microwaves, usually
mica, not a metal. The material can be obtained from places like MCM
Electronics which you then cut to size with a pair of scissors or a
paper cutter.

First, completely clean below, above, inside, and whatever of the cover
material is remaining. All traces of carbon and burnt on food must be
removed. In particular, you need to clean inside the waveguide above the
inside top of the oven as well.

Then run the oven (with the waveguide cover removed, if necessary) to
verify that there are no other problems (there probably are none).

Sometimes, you need to remove the outside metal cover in order to remove
the waveguide cover. There may be little plastic pins or snaps which
tend to get gummed up with burnt food and may be difficult to pry off
from inside the oven. If you do need to remove the metal cover, jot down
the locations of each of the screws (they are not always all alike) and
stay away from everything but the waveguide cover itself (especially the
high voltage components!).

That waveguide cover is not essential to the operation of the oven but
it does prevent food from entering the waveguide and getting trapped there.

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

== 1 of 2 ==
Date: Sun, May 29 2011 5:05 pm
From: "Phil Allison"

"Dave"

> Now believe I already have an ESR meter, though I didn't realize that was
> one of its functions. What I have is an Extech 380193 LCR meter, which
> tells me that a fairly new but run of the mill 1uF electrolytic cap out of
> my junkbox has 12.5 Ohms of resistance. If I were to try to use this to
> measure the caps in-circuit, how should I proceed? I am guessing that
> discharging the cap before touching my test leads to the solder pads would
> give me a reading, but I really hesitate to do this without some sort of
> suggestion that such is a safe proceedure for my meter. Am guessing that
> readings in the single digits indicate a defective device. Does this
> sound reasonable? No power to the circuit under test, of course, and
> likely will push in the power button a few minutes before beginning.
> Again, any advice is appreciated.

** Seen this ??

http://www.youtube.com/watch?v=zEA5MfllPdg

All you need to do is compare the ESR reading of a known good electro of
about the same ratings and size with the one under test. If the one under
test has say 5 times more ESR - it is useless or about to fail.

Often, with worn out electros, the ESR may be over 100 ohms.

.... Phil

== 2 of 2 ==
Date: Mon, May 30 2011 12:38 am
From: "Dave"

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94g5a0FfaiU1@mid.individual.net...
>
> "Dave"
>
>> Now believe I already have an ESR meter, though I didn't realize that was
>> one of its functions. What I have is an Extech 380193 LCR meter, which
>> tells me that a fairly new but run of the mill 1uF electrolytic cap out
>> of my junkbox has 12.5 Ohms of resistance. If I were to try to use this
>> to measure the caps in-circuit, how should I proceed? I am guessing that
>> discharging the cap before touching my test leads to the solder pads
>> would give me a reading, but I really hesitate to do this without some
>> sort of suggestion that such is a safe proceedure for my meter. Am
>> guessing that readings in the single digits indicate a defective device.
>> Does this sound reasonable? No power to the circuit under test, of
>> course, and likely will push in the power button a few minutes before
>> beginning. Again, any advice is appreciated.
>
> ** Seen this ??
>
> http://www.youtube.com/watch?v=zEA5MfllPdg
>
> All you need to do is compare the ESR reading of a known good electro of
> about the same ratings and size with the one under test. If the one under
> test has say 5 times more ESR - it is useless or about to fail.
>
> Often, with worn out electros, the ESR may be over 100 ohms.
>
>
> .... Phil
>

No, I haven't seen that before. *Thank you.* Need to check and see if they
have any others I could use. Am continually amazed by what I find available
on youtube.

Is there anything special you know about testing a cap in-circuit with a
meter like this? Am still a little worried about maybe damaging my LCR
meter. It was a Christmas/Anniversary/Birthday gift from my loving wife
some 8 or 10 years ago, and would like to keep it in good working order.
Can't tell you how much I appreciate your help thus far with the subject at
hand...

Thanks again.

Dave

==============================================================================
TOPIC: WHOLESALE all BRAND(UGGBOOTS,SHOES,CLOTHES,HANDBAG,WATCH,JEANS,JERSEY,T-
SHIRT,SHIRTS,HOODY,EYEGLASS,CAP,SHAWL,WALLT) and so on.
http://groups.google.com/group/sci.electronics.repair/t/1ee83c788187e854?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, May 29 2011 5:42 pm
From: jialiu

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==============================================================================
TOPIC: how to disassemble this AC Adapter?
http://groups.google.com/group/sci.electronics.repair/t/79c2e64c02b38c5d?hl=en
==============================================================================

== 1 of 2 ==
Date: Sun, May 29 2011 7:09 pm
From: Jeff Liebermann

On Sun, 29 May 2011 20:21:40 +0100, "N_Cook" <diverse@tcp.co.uk>
wrote:

>First is to remove any sticky labels that may cover a securing screw.

Good idea. However, I have yet to see such a screw on any laptop
power supply that I've torn apart. There usually isn't any room for
the required plastic pylon inside. There is also some safety rule
(double insulated???) that requires that the unit NOT create a shock
hazard by allowing the user to open the case. That's why they glue
the case shut, and not just snap or screw it together.

>Refining point 1 , place in vice with the weakest point in the line , where
>one of the cables exits.

I beg to differ. The ends are usually not very strong or well
secured. Compressing the plastic case at the ends is likely to break
the plastic, and still leave the long glue joints along the sides
intact. Best to break the long side joints first, and the ends will
just fall apart.

>A guitar plectrum is best to start with as a pry-bar as minimum damage,
>progress to screwdrivers etc later.

Yes, that should work. However, at $3/ea, I'm not thrilled.

I think the favored tool is a "spudger" from telco tools and the
favored tool for prying apart Apple products. Whatever works that
won't shred the insulation and shielding inside. Avoid anything with
sharp edges, such as a screwdriver.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

== 2 of 2 ==
Date: Sun, May 29 2011 7:12 pm
From: Jeff Liebermann

On Sun, 29 May 2011 13:30:46 -0700 (PDT), Robert Macy
<macy@california.com> wrote:

>The unit used to fail with the LED simply
>going OFF. If ON, unit was ok. Could be a lot between the AC mains
>and that LED, though.

The LED is across the output. If the cable or connector is shorted,
then the light will go out. Look for a short at the plug end of the
cable or loose shield wires on the output cable.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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