#61
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I know what ohm's law is. But, I don't care. That just isn't enough wattge. Period.
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#62
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Quote:
Then you put a second 39 ohm resistor in parallel with the first to increase the B+, which it did, but then the voltage started jumping around and one resistor started smoking? Was the first resistor still ok? Putting the two identical resistors in parallel would have reduced the voltage drop across the resistor(s) and, therefore reduced the power dissipated by the resistors(s) as well as splitting that power between the two. Neither should have overheated. Perhaps the second resistor was defective? If it were mine, I would try again with a fresh resistor and monitor the current in series with the resistor pair. jr |
#63
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The first resistor is what smoked, the second was fine. Strange, but true...unless the first resistor started to crispify at the first test, and I didn't notice.
At this point, Findm-Keepm's advice had got me this far, as far as the values of the resistors, and precise directions on how to hook things up and arrive at the proper specs. Bill Cahill's advice of a 25 watt resistor to do this job right will only cost me about $5, for a good Dale chassis mount resistor with a heat sink. That said, everyone here seems to agree that a 25 watt resistor here will certainly not hurt anything, at worst it's crazy overkill....at best, it's the proper part....so that's the way I'm going to go. I'll check back into this thread in a few days when the Mouser order arrives. I certainly do appreciate the input and education I've been given thus far
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#64
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Finally got the resistor in from Mouser. The only bad thing is that I must not have left that prior resistor in circuit long enough.....the chassis voltage with this one in line dropped to 243V. Should be at 255
I do have to say, the 18 ohm RH series Dale resistor I put in is getting HOT. Handling the set fine, but it sure is warm. Picture isn't fantastic, reception wise, but the tuner in this set isn't the greatest and I'm using clip leads for an antenna picking up signal from my agile modulator. I'm going to button it up for the moment and move it to cable and see where we're at. The chassis voltage is off by -12V, meaning that I'll have to probably order yet another resistor, but I want to let it play out a little where it is and see how it looks. The picture filled out nicely as opposed to where it was before.
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#65
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Here's where I'm at right now. Seems to have some slight blooming, which I assume is due to the low voltage on the chassis.
http://www.youtube.com/watch?v=_bUxH...ature=youtu.be
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
Audiokarma |
#66
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IMHO you should prepare for smoke! Something is wrong, the set should not be drawing enough current to get an 18 ohm 25 watt resistor *really* hot!
Calculator: http://www.crownaudio.com/ohms-law.htm If you plug in 18 ohms and, say 15 watts (my estimate of what it might take to get a 25 watt resistor fairly hot), you will find a voltage drop of about 16.4 volts (too much drop) and a current of about 900 ma! Since the original rectifiers were only 340 ma or so, it would appear that the set is drawing more current than it should, just my 2 cents, jr |
#67
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If that's the case, what the heck would cause that in a TV that by and large is running as it should?
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#68
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I don't know, perhaps an infant failure of one of the new electrolytics. Can you measure the current in series with the resistor?
Am I correct in assuming that the resistor is indeed, bolted to the chassis? If not, it could reach a high temperature at less than its rating. jr |
#69
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No, at the time, I had the resistor put in with clip leads. I didn't want to hard mount it to find out I needed a different value.
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#70
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Quote:
jr |
Audiokarma |
#71
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Add to that the blooming. There was no blooming of the picture when the seleniums were in place. Also now, if you look really hard at the video, you can see a very light line going down the center of the screen, which isn't really visible on some stations. Is that horizontal foldover?
So then we're left with the question, is the blooming caused by the low B+, or is the same component causing the blooming and low B+, dragging the chassis voltage down, and sucking current? First thing I'm going to do is test the diodes. Not sure if another diode in series would help matters much, as I got 3 watt diodes. Next thing, I'll re-test the tubes. Beyond that, I just don't know.....
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#72
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If you connected a doubler cap backwards that could do it.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#73
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I would first try to measure the current in series with the resistor, to see what the set is drawing off of the B+ line... that should answer the question; "is the set drawing too much current or is the power supply not working correctly?".
jr |
#74
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I agree checking the current is one of the best ways to find out what's happening. But, the blooming, along with slightly short width, which he told me about, and, the white line in middle, which sounds like slight horizontal fold over, obviously, hv is low. I'm not sure if that is caused by low voltage, or, something wrong in hv section. In fact, if the screen resistor on the horizontal output, or, even the cathode resistor on same, if it uses one, which often they do, that would cause that section to draw more current, causing the power supply to drag down.
Bill Cahill
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#75
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Went to measure the current draw, but then realized that the ammeter function on my meter isn't working. Have to go pick one up today or tomorrow.
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
Audiokarma |
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