You have to look for dry solders in the region between vertical output transistor and primary side of the flyback (LOPT) transformer. Youd dont need a service manual for this. Just re-soldering circuits as Benimur suggested will do the trick..
Toshiba 27DF46 Service Manual available for download from NoDevice.com
http://www.nodevice.com/manual/newmans/27df46pdf/get32242.html
http://www.nodevice.com/user_manual/toshiba/television/27df46.html
Hi there
Try replacing the electrolytic capacitors in the power supply section.
I started with replacing (2) 860uf 180v caps just after the bridge
rectifier and continued along the circuit. Some (15) or so capacitors
later,it finally cleared the the horizontal bars and lines and the high
pitched noise. It also fixed another intermediate problem of no video,
when turning on the power.
Thank you for using FixYa. Have a nice day and please remember to rate this solution as FixYa if it helps you.
Thanks
Dustin Ellse (BearWeb)
Ok on the dboard This is your most probable cause after looking at the circuit diagram you need to replace 4 10V10 CAPACITORS.
the 2 ZENER DIODES # 10.0V 1W .
and this IC SEMICONDUCTOR LA1460 kit and you should be set.
test em to make sure and replace them as needed that website has anything that can be blown.
Hope this helps,
Nate
But this is your most likely problem that i laid out to you. Im not just giving you what it could be. Im giving you what it is, As i trust with your experience you described. This should be no problem for you.
i have access to the circuit diagram if you need help on a replacement walk through.
That IC isnt even in the unit Robotek i Have the circuit diagram do you? or you just blowing smoke. Cause none of what your saying is right yet your trying to discredit someone. You dont know much about IC replacement if all you have to do is replace an ic theres a little bit more to the kit then that. You need a diode and a cap or the IC will blow again. But you do your thing if it helps.
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Hi
The verticleICis mounted on a heatsink, and you will find thicker wires connected to the yoke plugged in nearby. Cahnge all the capacitors about the area also, as they have a tendency to blow chips,or cause other problems. This about does a vertical stage repair. Take the back off and have a look for the yoke connection like I have said.Check before anything else that the chip itself is not just dry jointed. This will cause vertical collapse also. The only other thing may be an open circuit yoke.
I am more than happy to answer any other questions you may have about
it, please get back to me here, or use the ASK function to go straight
to me :) If you are still unsure, have problems, or we need to look at
the situation more deeply, then before you give a rating for this
advice, hit the ASK button
Thanks for using FixYa, If you consider the advice I have given you as
sound, a FixYa rating is a great reward for my efforts to help you.
Cheers.
regards
robotek
It is a fault in the vertical not horizontal stage, so focus your efforts there to begin with.
yes, the fault may be marginal. Capacitors are a likely cause of this condition also. I generally just rebuild the area, clean old heatsink paste away, and use new compound. I use 2% silver content solder for its better heat stress strength
DON'T FORGET - DANGEROUS VOLTAGES ARE PRESENT
even with power disconnected !!! Be sure to Work electrically safe.
If the problem comes and goes however, it is probably more likely to be dry joints. Start with resoldering first, then if it does not improve capacitors and vertical IC would be my call
Here is another repair method relaying the same message about the verticle IC by one of our Top Experts, Premtech
it's most likely the the vertical IC an
LA7847-E has probably become ring-cracked at the point where the pins
are soldered to the pc board.
Depending on how long it has been
allowed to arc the IC may have failed also, but they are not terribly
expensive or difficult to repair - at least not here in the shop.
The
main board has to be removed. Locate the vertical IC - it will be
mounted to a metal heat sink and the IC will be stamped LA7847. Then
turn the board over and inspect where the pins are soldered to the foil
side of the board. One or more will look ring cracked or fractured all
the way around the pin. At this point you have two options, carefully
reflow solder over each pin and put it back together or replace the IC
by de-soldering it and removing it from it's heatsink. remember to use
a good heat sink grease when applying the new IC.. There should also be
a couple of caps in pretty close proximity to that IC... One should be
about 50v/100uf and in the shop here we test em all... You might also
just replace that one for good measure - they're not expensive either...
it can be said that there are many ways to skin a cat, there is only one way to skin this one. The solutions given relating to the verticle output IC are correct. I hope that the extra solution I provided from Premtech helps clear that up. Cheers
@midwest. the LA1460 is a low power dip chip... not a vertical output chip. What part of the circuit are you looking at?
no problem glad to be of help. The chasis generally slide into rails on the front section, and also into the rear casing. It is not hard to manouver it about to get access to the verticlechip. They slide out and with not much "unhooking" of loom dress, you can turn the chassis over. Will post back to here tommorrow. Cheers
regards
robotek
----When the picture becomes a horizontal line, I can get the picture back by turning off the TV and
turning back on after several minutes. It will then operate for 5 to 10 minutes before failing....
Sounds like you are talking about an intermittent fault. This is classic behaviour for heat stressed dry/cracked solder joints about the VerticalOutput chip. The chip may even be desoldering itself from overheating in the first place, the conditions promoting the overheating being caused by failing overheated, vented out caps mounted near the heatsink.
Have you got to the chassis yet?
To help a little with the repair provess, I have found a link so you can download the service manual for the 32DF46. Is the 32 inch version of the set you have, but same chassis i believe. The LA7847 comes up for both models, so the vertical circuit will be relatively the same. It is marked as IC401,and is towards the center of the main board near the flyback (eht) transformer
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The symptom is a vertical output problem (and has nothing to do with the tube itself). It is very common and is the result of some capacitors in the vertical circuit deteriorating with age. As long as you get it fixed before any active components fail (like the output IC) it is generally a $50 - $75 repair. If the output fails, then add another $25 - $50 to the repair. There is always the possibility that the IC has a thermal failure already, usually meaning a $75 - $100 repair; but the capacitors are the typical fault. Hope that helps..........
Hi,
Often culprit would be the vertical IC. The are a fe instances that it could just be a resistor that has opened or increased its resistance.
Basic tools (DVM, soldering iron hand tools) should be enough. Perhaps you would not even need a service manual but a schematic would help.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards.
Thank you for using FixYa.
Hi again,
A bit of clarification pls, is your Toshiba a 27AF61 and additionally, would it have a chassis number possibly on a sticker either on the rear cover or on the aluminum heatsink near the flyback transformer.
Looking forward to your postback.
Cheers.
Based on your last post, then i am inclined to think that there is no component failure but rather a case of cold solder. Corrective procedure wold require re-application of heat with a soldering iron and perhaps a dab of soldering lead where required.
robotek has given you a way of identifying the vertical IC.
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THIS PROBLEM DOES NOT REFER TO A PROJECTION TV.
IT IS FOR A STANDARD BROADCAST 27"CRT TV.
Thanks for the quick response but the answer is too vague. Without a schematic it is impossible to know which is the vertical IC
or which resistor you are referring to.
What else beside the vertical control circuit
could be the problem? Could it be the high voltage supply---although probably not since the horizontal scan is working.
I need enough info to fix it.
One additional piece of info----When the picture becomes a horizontal line, I can get the picture back by turning off the TV and
turning back on after several minutes. It will then operate for 5 to 10 minutes before failing. I assume that this implies a fault that is marginal and heat sensitive.
The model # of the TV is 27DF46. I haven't looked for the chassis # but the S/N is
BAB614022413 A and was manufactured in Feb 2006.
Maybe the S/N reveals some info about the chassis #.
Hi Robotek,
It looks like the Premtech solution is detailed
enough to attempt a fix. I have only a couple of simple questions. When the back cover is removed, is the main board containing the LA7847 easily identified and is it easily removable--is the board connected to the rest of the TV thru a set of connectors?
(I am aware of the high voltage even when powered off).
It is late here so I will be back to you tomorrow. We are getting close. Thanks
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