Toshiba TV29C90 problem; Image fades to black...

I have a few parts units around, what part exactly do you need? MA2B027 or MA27A1?

Dan
 
On Monday, April 15, 2002 at 4:56:13 AM UTC-7, Jan Wemmel wrote:

Even that I have been trained as a Radio and Television Technician in
Germany (admittedly 10years ago) and that I have a degree in IT and
Telecommunication, I have never seen a diode with varistor characteristics.
Click to expand...

Diodes with specifications that make them suitable for temperature compensation
of power amplifiers are marketed as 'compensating diode', 'varistor',
or 'stabistor', and I wouldn't be surprised to see 'thermistor' as well.
Telephone company 'varistor' units are antiparallel diode pairs.

If you have a working unit, and a multimeter with 'diode check' feature,
any another diode with the same forward voltage will be a good replacement.
 
Il giorno martedě 5 maggio 2015 23:32:46 UTC+2, dansabr...@yahoo.com ha scritto:
I have a few parts units around, what part exactly do you need? MA2B027 or MA27A1?

Dan
Click to expand...

Hi Dan,
thanks for replying.
I think the right replacement would be MA2B027WA.
How many of them do you have? Would you able to ship me some, let's say 10, of them (to Germany)?
Do you happen to know a suitable replacement which is easy to find nowadays?

I think those "varistors" can't be replaced with normal silcon diodes as correct biasing would require them: I did once a try and I was about to blow up the final stage (again).

Thanks a lot in advance,
-- Marco
 
On Tue, 5 May 2015 13:49:26 -0700 (PDT), cosentino.ma@gmail.com wrote:

Il giorno lunedě 15 aprile 2002 13:56:13 UTC+2, Jan Wemmel ha scritto:
Thank you very much to everybody who wrote a reply, it is good to see that
there is so much knowledge out there.

Even that I have been trained as a Radio and Television Technician in
Germany (admittedly 10years ago) and that I have a degree in IT and
Telecommunication, I have never seen a diode with varistor characteristics.
Unfortunately, the source for the part that Paul mentioned does not stock
the MA27A1, only the MA27A which is totally different. Panasonic in the US
offer the part via their website (http://www.pasc.panasonic.com) but this
service is not offered in Europe (UK), however the shop that Paul
recommended will get hold of the part from Panasonic. Do not try to get hold
of part from Panasonic directly in Europe a service manual would arrive in
6! weeks and would cost you Ł20+ VAT and postage (approx. $40). I got a
manual within 2!days from here http://www.divdev.fsnet.co.uk/man.htm. I can
only recommend the service!!!

Anyway, Goran was absolutely right, the Diode (varistor) controls the basis
voltage on a transistor (Q312) that controls the bias voltage of the amp.
Currently the transistor opens up completely and the transistor have the
full negative voltage (-53V) on their basis (not very good, luckily the
protection is VERY quick, I would be very upset to have seen my B&W speakers
go up in flames). I assume the diode has move the basis voltage of Q312 a
little causing the transistor to open up completely. However, I think there
is probably an additional problem because when I measure the resistance
against the chassis the right and left channel a completely different. Still
a lot of fun to be had... But I think the repair is still worth it as the
amp, even compared to todays amps still has some very good characteristics
and do you know of an end user amp that has two power supplies, one for each
channel (transformer, rectifier AND caps)?

Again thank you very much for your help!!

Jan



Hi, sorry for resuming a 13 years old thread.
I have a problem similar to Jan's. I did some research and found a possible replacement candidate fo the diode: Panasonic MA2B027 (datasheet here http://www.datasheetarchive.com/dlmain/Datasheets-24/DSA-471901.pdf).


It seems there are several different versions of the diode (variants A/B, WA/WB, TA/TB, QA/QB). I think in my case the WA/WB variants are the correct ones (see also thread http://www.audiokarma.org/forums/showthread.php?p=8216699#post8216699)

BUT the part shows as discontinued in Panasonic website: http://www.semicon.panasonic.co.jp/en/products/detail/?cat=CXZ7000&part=MA2B027

Any idea for a replacement?

Thanks in advance
Click to expand...

Here is the modern sub. from Best Buy's part division. 45 days to
restock but you can order it now.
https://www.partstore.com/Part/Matsushita/Panasonic/RF088/Matsushita/Panasonic/MA27B1/New.aspx

---
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http://www.avast.com
 
Il giorno mercoledĂŹ 6 maggio 2015 23:50:15 UTC+2, Chuck ha scritto:
On Tue, 5 May 2015 13:49:26 -0700 (PDT), ... wrote:

Il giorno lunedě 15 aprile 2002 13:56:13 UTC+2, Jan Wemmel ha scritto:
Thank you very much to everybody who wrote a reply, it is good to see that
there is so much knowledge out there.

Even that I have been trained as a Radio and Television Technician in
Germany (admittedly 10years ago) and that I have a degree in IT and
Telecommunication, I have never seen a diode with varistor characteristics.
Unfortunately, the source for the part that Paul mentioned does not stock
the MA27A1, only the MA27A which is totally different. Panasonic in the US
offer the part via their website (http://www.pasc.panasonic.com) but this
service is not offered in Europe (UK), however the shop that Paul
recommended will get hold of the part from Panasonic. Do not try to get hold
of part from Panasonic directly in Europe a service manual would arrive in
6! weeks and would cost you Ł20+ VAT and postage (approx. $40). I got a
manual within 2!days from here http://www.divdev.fsnet.co.uk/man.htm. I can
only recommend the service!!!

Anyway, Goran was absolutely right, the Diode (varistor) controls the basis
voltage on a transistor (Q312) that controls the bias voltage of the amp.
Currently the transistor opens up completely and the transistor have the
full negative voltage (-53V) on their basis (not very good, luckily the
protection is VERY quick, I would be very upset to have seen my B&W speakers
go up in flames). I assume the diode has move the basis voltage of Q312 a
little causing the transistor to open up completely. However, I think there
is probably an additional problem because when I measure the resistance
against the chassis the right and left channel a completely different. Still
a lot of fun to be had... But I think the repair is still worth it as the
amp, even compared to todays amps still has some very good characteristics
and do you know of an end user amp that has two power supplies, one for each
channel (transformer, rectifier AND caps)?

Again thank you very much for your help!!

Jan



Hi, sorry for resuming a 13 years old thread.
I have a problem similar to Jan's. I did some research and found a possible replacement candidate fo the diode: Panasonic MA2B027 (datasheet here http://www.datasheetarchive.com/dlmain/Datasheets-24/DSA-471901.pdf).


It seems there are several different versions of the diode (variants A/B, WA/WB, TA/TB, QA/QB). I think in my case the WA/WB variants are the correct ones (see also thread http://www.audiokarma.org/forums/showthread.php?p=8216699#post8216699)

BUT the part shows as discontinued in Panasonic website: http://www.semicon.panasonic.co.jp/en/products/detail/?cat=CXZ7000&part=MA2B027

Any idea for a replacement?

Thanks in advance


Here is the modern sub. from Best Buy's part division. 45 days to
restock but you can order it now.
https://www.partstore.com/Part/Matsushita/Panasonic/RF088/Matsushita/Panasonic/MA27B1/New.aspx

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
Click to expand...

Hi Chuck,
thanks for your reply.
Is there a place where I can find the datasheet for this part you mentioned? I just want to double check it suits as a replacement and my inability to find the datasheets makes me a bit reluctant to just place an order and see what arrives.

Thanks in advance,
Marco
 
On Friday, May 1, 1998 at 2:00:00 AM UTC-5, Paul Degneau wrote:
I have a Dumont model 1062 oscilloscope that I bought recently at a swap
fest. The previous owner had no manuals or anything for the scope, I
managed to rig a power cord and get probes for it, but I would like to get
the manuals for it. If anyone knows where I can get the user/service
manuals for this scope please reply to the group or email me.

Also this scope seems to have a vertical and/or preamp problem. Channel 1
is slightly fuzzy but seems to be accurate, channel 2 is very clear but the
vertical size of a trace varies depending on were it is vertically on the
screen. If anyone knows what may be wrong I would appreciate any info.


Thanks,
Paul Degneau
degneaup@msoe.edu
Click to expand...

I purchased the same scope again with no manuals. I know it works, I just can't set it up to get a reading on anything. Searching the web now. I would appreciate any advise. Anybody feel free to email me or send any helpful links.

thanks
 
On Sun, 10 May 2015 09:23:18 -0700 (PDT), twistoffateband@gmail.com
wrote:

On Friday, May 1, 1998 at 2:00:00 AM UTC-5, Paul Degneau wrote:
I have a Dumont model 1062 oscilloscope that I bought recently at a swap
fest. The previous owner had no manuals or anything for the scope, I
managed to rig a power cord and get probes for it, but I would like to get
the manuals for it. If anyone knows where I can get the user/service
manuals for this scope please reply to the group or email me.

Also this scope seems to have a vertical and/or preamp problem. Channel 1
is slightly fuzzy but seems to be accurate, channel 2 is very clear but the
vertical size of a trace varies depending on were it is vertically on the
screen. If anyone knows what may be wrong I would appreciate any info.


Thanks,
Paul Degneau
degneaup@msoe.edu

I purchased the same scope again with no manuals.
Click to expand...

"Insanity: doing the same thing over and over again and expecting
different results".
Albert Einstein

>I know it works,

How do you know it works? Can you see a trace? Can you see anything
on the screen? Is it a line, blob, or a smear? Does the beam finder
work? Or do you know it works because the guy who sold it to you told
you that it works? Caveat Emptor.

Here's a photo:
<https://static.kupindoslike.com/Osciloskop-Dumont-1062-dvokanalni-20-Mhz_slika_O_3315401.jpg>

> I just can't set it up to get a reading on anything.

What do you mean by "reading"? I believe the correct term is that you
can't see a trace or waveform display.

Searching the web now. I would appreciate any advise. Anybody feel
free to email me or send any helpful links.
Click to expand...

Well, I can't offer any suggestions unless you disclose what you're
seeing on the screen. We can then precede from there.

Hint: Anything that old is going to have problems with "dry"
electrolytic capacitors. Have they been tested with an ESR meter or
hopefully replaced?


--
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
 
In article <1e900d6e-c0b0-4ed7-81f9-472b35e5354a@googlegroups.com>,
twistoffateband@gmail.com says...
On Friday, May 1, 1998 at 2:00:00 AM UTC-5, Paul Degneau wrote:
I have a Dumont model 1062 oscilloscope that I bought recently at a swap
fest. The previous owner had no manuals or anything for the scope, I
managed to rig a power cord and get probes for it, but I would like to get
the manuals for it. If anyone knows where I can get the user/service
manuals for this scope please reply to the group or email me.

Also this scope seems to have a vertical and/or preamp problem. Channel 1
is slightly fuzzy but seems to be accurate, channel 2 is very clear but the
vertical size of a trace varies depending on were it is vertically on the
screen. If anyone knows what may be wrong I would appreciate any info.


Thanks,
Paul Degneau
degneaup@msoe.edu

I purchased the same scope again with no manuals. I know it works, I just can't set it up to get a reading on anything. Searching the web now. I would appreciate any advise. Anybody feel free to email me or send any helpful links.

thanks
Click to expand...

i good one of those scopes, I was just moving it today actually trying
to clean up the shop with very little luck I may add.

The last time I used that one I know it worked but I had to repair it
once. The HV multiplier failed and there was no parts for it so I used a
ECG replacement HV multiplier for TVs, wrapped it with foil and jammed
it in there :) It works, I can't say that it has caused any side
effects..

I suppose if some one was willing to pay the shipping I could let it go
:)

Jamie
 
On Fri, 8 May 2015 12:39:15 -0700 (PDT), cosentino.ma@gmail.com wrote:

>MA27B1

Don't know of one, but this is the substitute that Panasonic
recommends.

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Il giorno martedě 12 maggio 2015 18:58:39 UTC+2, Chuck ha scritto:
On Fri, 8 May 2015 12:39:15 -0700 (PDT), cosen...@gmail.com wrote:

MA27B1

Don't know of one, but this is the substitute that Panasonic
recommends.

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
Click to expand...

I ordered some MA2C029WA from ic-chips.com. We will see if it suits....
Quite pricey the expedition costs to Europe... not sure if it's worth but I'm sentimentally bound the my Technics. Probably a bad thing :D

I'l try with these you recommend if those I ordered turn to be a not suitable / bad replacement.

Best,
Marco
 
I have a KV36XBR450 accidentally 230 volts was applied and power off. Checked and replaced the fuse but it burns again,please let me know what all could suspect
 
The OP in this cas probably had a shorted video output IC rsulting in the failure of the 220 volt supply to the CRT board.

Resurrecting years old threads doesn't weork well here. I see many gmaiers doing it, probably because of how gmail presents the threads, especially after a search.

Check your other thread. Answers are there.
 
To reset the Amplifier, please turn off the amplifier, press and hold the channel (+) botton and press power botton
 
<KLayton888@aol.com> wrote in message news:6dc4947e-34f3-45eb-91f3-e970a8093315@googlegroups.com...
On Saturday, July 18, 2015 at 8:50:33 AM UTC-7, Snuffy Hub Cap McKinney wrote:
Anyone know where to get a replacement timer for this unit? B&D does not have stock.
Timer failed after a few weeks and stays on until manually turned off.

I wonder how to find out if there is a recall on this product. This is a fire/injury hazard.

Previous oven was also Black & Decker and used for 20 years. Was still working when replaced because heating elements started to heat unevenly.

I would not recommend the TRO480BS. Many problems -- those I recall are door can't be adjusted to close evenly, letting too much air in/out on one side. Top and bottom heaters don't heat equally - have to turn toast over to brown both sides, etc.

Try posting in sci.electronics.repair
Click to expand...

Thanks.
 
On Sat, 18 Jul 2015 08:59:50 -0700, Snuffy \"Hub Cap\" McKinney wrote:

KLayton888@aol.com> wrote:
On Saturday, July 18, 2015 at 8:50:33 AM UTC-7, Snuffy Hub Cap McKinney
wrote:
Anyone know where to get a replacement timer for this unit? B&D does not
have stock.
Timer failed after a few weeks and stays on until manually turned off.

I wonder how to find out if there is a recall on this product. This is a
fire/injury hazard.

Previous oven was also Black & Decker and used for 20 years. Was still
working when replaced because heating elements started to heat unevenly.

I would not recommend the TRO480BS. Many problems -- those I recall are
door can't be adjusted to close evenly, letting too much air in/out on one
side. Top and bottom heaters don't heat equally - have to turn toast over
to brown both sides, etc.

Try posting in sci.electronics.repair

Thanks.
Click to expand...

Considering it is most likely manufactured in China, you may try your luck on
AliExpress. Searching for "oven timer" pops up a decent lot of mechanical
timer units.
You'd have to check the markings on your timer for a match.
And you'd need the patience for it to arrive :)

Cheers!
 
On Sat, 18 Jul 2015 08:59:50 -0700, "Snuffy \"Hub Cap\" McKinney"
<Snuffy-Hub-Cap@Livebait-McKinney.com> wrote:

KLayton888@aol.com> wrote in message news:6dc4947e-34f3-45eb-91f3-e970a8093315@googlegroups.com...
On Saturday, July 18, 2015 at 8:50:33 AM UTC-7, Snuffy Hub Cap McKinney wrote:
Anyone know where to get a replacement timer for this unit? B&D does not have stock.

I would not recommend the TRO480BS. Many problems -- those I recall are door can't be adjusted to close evenly, letting too much air in/out on one side. Top and bottom heaters don't heat equally - have to turn toast over to brown both sides, etc.

Try posting in sci.electronics.repair

Thanks.
Click to expand...

The B&D TR048BS has one good feature... it's cheap. Typically about
$30 when on sale. According to a few reviews that I skimmed,
everything else about it is marginal. If a typical parts vendor:
<http://www.ereplacementparts.com/black-and-decker-tro480bs-toaster-oven-parts-c-4167_124449_182647.html>
wants $11.29 for the timer knob, I can imagine what a replacement
timer would cost. Methinks buying a replacement toaster oven might be
cheaper. Or, as somone else suggested, try AliExpress. This looks
like a possible:
<http://www.aliexpress.com/item/30-minutes-pressure-cookers-microwave-oven-timer-parts-mechanical-timer-type-250V6-5A/1573000112.html>

You didn't bother to mention whether the mechanism or the contacts
failed on your existing timer. If the contacts, I suggest you take it
apart and clean the contacts, which might fix the problem.

Incidentally, I use a similar B&D toaster oven for reflow soldering
electronics:
<http://802.11junk.com/jeffl/pics/repair/BGA%20reflow/index.html>

--
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
 
On Saturday, November 22, 1997 at 3:00:00 AM UTC-5, Randy B wrote:
Greetings Group,

I picked up an Infrared Motion Detector from a Flea market for a
dollar. It's a Telko "S002M", it has what looks like a DTMF style keypad
on the front and a small earphone type jack on one side. I wasn't able
to get any kind of instructions with it.

Does anyone know how to set the code for this? Or how to get ahold of
this company? Any response would be appreciated.

Randy Bray
Corvallis, OR.
Click to expand...

If you take the battery out and wait a minute or so till the unit fully discharges, then put battery back in and press 0, that is a zero, and then press* that is a start, then enter code up to 12 digits and then *star, your code will be set! Have fun. I have two units that I haven't used for 15 years and just reset mine.
 
Thanks for the replies.

Is there anywhere online I can download a service manual for this? Haven't
managed to find a belt/kit yet.

Your VCR needs a belt job. When these things sit idle for long period
of time, the belts that drive the loading deck and tape transport
mechanism stretch and become too loose to make the mechanical stuff
work.

Don't know how much a belt job would cost now, but when my daughter
ran a TV
repair shop (90s era), they charged about $50 plus the cost of the
belt kit.
If you're mechanically inclined, you can do it yourself if you can
find the
proper belt kit. Here are some links to vendors that I have bought
TV, VCR,
and other A/V parts from:
http://www.mcmelectronics.com/
http://www.matelectronics.com/
http://www.smcelectronics.com/
http://www.parts-express.com/
http://www.electronix.com/
http://www.elexp.com/
http://www.studiosoundelectronics.com/
You sould also search Google for VCR Belt Kit NV-SD260B and see what
turns up. Good luck with the repair. VCRs are long obsolete and
parts are getting scarce.

Dave M

M.Joshi wrote:

I dusted off a Panasonic NV-SD260B VHS recorder yeterday to archive
some old tapes. It worked for a while, but no longer loads any tapes?
No matter how far I push the tape in, it won't load it into the
mechanism.
I have taken the cover of the unit off but can't see anything
obvious?
Click to expand...
 
Hello Ian,

I did wonder if it was the tape sensor post - I have had to change the lamps
in the past on another unit.

However, I thought that was just to sense tape end? They appear to be the
IR type. The tape isn't being lowered into the mechanism so I guess it probably
is a snapped belt?


"M.Joshi" <M.Joshi@eternal-september.org> wrote in message
news:4f7214e111488d2b604a399ff55@news.eternal-september.org...

I dusted off a Panasonic NV-SD260B VHS recorder yeterday to archive
some old tapes. It worked for a while, but no longer loads any tapes?
No matter how far I push the tape in, it won't load it into the
mechanism.

I have taken the cover of the unit off but can't see anything
obvious?

The old favourite was the sensor bulb blown - its a thin vertical post
in the middle of the deck that pokes up a hole in the bottom of the
cassette.

Later models used an IR LED - AFAIK: these never caused problems, so
might be a belt job as others have suggested.
Click to expand...
 
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