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#136
03-26-2013, 09:38 PM
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Oh... Maybe Firebird can find some ID on the amplifier module for us?
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#137
03-27-2013, 03:48 PM
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I removed amplifier module to take pictures. When i reinstalled picture came back on folded in the middle with black bars on the sides. Then it changed to horizontal lines with black bars on the side. Then back to the folded picture.
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#139
03-28-2013, 11:53 PM
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I will probably get in trouble for this but could a bad flyback cause such symptoms? No i did not replace parts with the power on. I did turn the adjustments on the sound amp and returned them as close as i could to original with no effect. The only thing that seems to effect anything is the adjustment on the horizontal oscillator board, with no change except it went from lines to picture. It was still folded in the middle. I have had electronics training but no experience repairing tvs so i have never seen this before.
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#140
03-29-2013, 03:12 PM
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Well....
Can you post a screen shot of what the picture looks like? The flyback would have nothing to do with sound. I'm pretty sure your set has a flyback AND a high-voltage tripler. Now either of those could cause a folded picture if there was not enough high-voltage, but a screen shot of your set would help. Your audio issue tho, would have nothing to do with that, so I'm wondering if you have 2 seperate problems going on? Is there anyone in your area you could take it to for repair? You might be in over your head on this one. No offense, as I am NOT good on solid state stuff myself, especially a Magnavox. So, I was trying to go thru your posts from the beginning. What was the original issue? I think you said no picture? IIRC you replaced the horiz output transistor?
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#141
03-31-2013, 04:57 PM
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I have been told several times that the flyback powers the sound. This has led me to believe it is either the flyback or tripler or both. I have tested the resistors and diodes. I found no defects. There are very few repair people left in this area and even fewer with knowledge of this type of television.
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#142
03-31-2013, 07:00 PM
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Well... whoever told you that gave you some major MISinformation, and if it was someone from this forum (which I doubt) I would like them to post and explain why they think that is. Audio has NOTHING do do with your high-voltage circuit. NOTHING.
To make it simple... a flyback and tripler act as a step-up device to deliver the 25KV needed to light up your screen. In your set (1981 Vintage) a flyback rarely fails, It's usually the tripler, and if that were bad, your symptoms would be either : NO picture, or poor focus, or.. if you have a high-voltage probe, you may find that the set is not putting out the 25KV needed. In the years I worked in a repair shop, never once, was a no audio problem caused by anything in the high-voltage side.
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#143
03-31-2013, 07:15 PM
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Quote:
Until we got pictures, nobody here even KNEW that your set had the power amplifier. The flyback supplies voltages allover the chassis, but NOT that power amplifier. Notice the power transformer... black thing... beside the power amplifier? That would be a power transformer for the amplifier.
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#145
03-31-2013, 09:47 PM
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Not sure yet what you turned on the amp. Were there any labels? I doubt turning anything on the amp caused the picture problem. A bad connection on the horizontal board would be more likely cause the problem, and touching the adjustment on the board made the picture come back. If anyone knows the sams number for a set with that amp I will look up the amp schematic. Shame you can't get the entire chassis here to West Tn. I would look at it for you. It would be to fragile to ship, but if you happen this way let me know. I have a test jig and really don't need the CRT or cabinet.
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| Audiokarma |
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#147
04-01-2013, 07:44 AM
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Quote:
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#149
04-01-2013, 02:19 PM
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Do not turn any adjustments unless you know what they are for. Guys the problem is that the amplifier schematic is not part of the sams set. I can not find any reference to an external power amplifier, yet there it is. I have been unable to find a schematic for that amplifier. i could possibly fix it if I had it here, but he is 7 or 8 hours away from me. if the set still has the on board sound module, it may be possible to connect one set of speakers to the speaker level output of that module. This is not where the external amp connects to the chassis, unless that set does not use the sound module called for on the Sams schematic. Firebird, you have more than one problem. As long as you have a picture concentrate on getting the sound working. Then, using the schematic you can troubleshoot the color problem. You still may have solder problems around the horiz. osc. board. The flyback and tripler are not your problem. They are fine. On newer sets most if not all of the B+ voltages came from the flyback windings. This is not the case on your set. Your flyback is fine, and would not cause any sound issues. Not having the schematic I would first check the output transistors or IC on the external amplifier. Then the driver transistors. Replace any that are bad and check any emitter resistors. Be sure the solder connections are good. I would then check every electrolytic capacitor with an ESR meter or just replace them all. Do not turn any adjustments. Right now we do not know what they are for, and if they were bias adjustments could cause you to blow new transistors. If there are no output transistors, there should be an output IC. Check it for shorts. Replace it if necessery. How may connections go to the external amplifier? If it only has power, signal and speaker out. I may be able to fix it without the rest of the chassis. Let me know. After you get sound fixed, you can move on to the Horiz Osc board, and its connections. This will get you a stable black and white picture. Then move on to the color issue. The color is processed through about 3 differnt modules, none of which will cause sound or unstable picture issues. So get the other problems solved first, the move to the color problem. Solder connections were a huge issue with these sets, I know you resoldered some of the connections, did you pull the chassis out and look at the bottom of the motherboard for bad solder connections?
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