#481
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#482
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Today marks about 3 years since i completed my FADA, and it's still going strong!
http://suzaku.live-evil.org/0816231928.mp4
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#483
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Nice!
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#484
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OK...
this is a bit weird. This tube has ALWAYS been brighter in this TV, the 1st video amp, 6AU6, it flashes MUCH brighter when first turned on, then dims down a bit, but is always brighter than all the other tubes, but always seemed to work, an RCA branded tube. may be one of the original tubes. http://suzaku.live-evil.org/0209241844b.jpg Just to see what would happen, stuck in a NOS sylvania, and it warms up slow like the others, and is not as bright as the RCA that was removed, not seen a tube act like this before, almost as if they mis branded a 4AU6 as a 6AU6 :O weird.
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#485
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Connect is to 6.3V and measure the heater current. Should be 300ma. If significantly higher, something is amiss.
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Tim |
Audiokarma |
#486
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At 6.3v dc it's 368ma, after the large warm up spike.
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#487
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Likely a couple of loops of the heater have shorted together, reducing the total heater resistance.
jr |
#488
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Most likely, just know that it IS an RCA, could be an original from when the set was made.
Hard to see any kinds of date codes on it, not sure how to decode them anyway, Looks like under the “Made in USA” 8 (or B)-71. No idea if that's what it says or what it means.
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#489
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Thankfully the planet is still littered with NOS 6AU6's
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#490
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correct,
Cause the video out was acting a little weird, I have some NOS tubes on the way to replace what's most likely 50+ year old ones. Thomson France 6AU6WB Military Grade (1st video) I had other 6AU6s, but, you can't turn down mil spec! 6K6GT (2nd video-output) thank you audiophiles for making this tube cost more than it should. 6AL5 (video det/ dc restoration) the only tube not with an inflated price.
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Audiokarma |
#491
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A weird thing about this set is, the schematic shows the HV to be at 9k, which is the nominal voltage for a 10BP4, standard CRT for the RCA 630TS of which this is a clone of.
HV tests puts output at 10k at mid brightness. However. FADA put in a 12LP4, and specs show that to have a nominal voltage of 11k. Did they flub things a but to put this tube in? It does work, but I can turn up the brightness to a point that it overloads the HV and blooms. W/O a load, the FBT is putting out about 10.2k, this seems OK for one made for 9k. :O
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#492
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#493
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Odd behavior with brightness / contrast localized.
Power supply seems to be acting up a bit, it's NOT the pair of 5U4GB tubes, tried new, no change. Have noticed slight changes in brightness / contrast as the set is in operation, could not work out the cause, then noticed that the horizontal width would change in relation to the sound when vol was up high, pulled the 6K6GT audio output to try another I had, brightness / contrast came up substantially, tube swap made no change. Working much better with audio output removed, possible sign that the bleeder resistor network which is still original save for 1 section is starting to fail. However, not willing to pull it apart just yet, as this chassis originally did not have audio output to start with, I'm going to use a band-aid method to keep it going till I'm ready to work on it again, at which time I'll also attempt to do a IF alignment, which it really needs. So, in the meantime, remove the audio output and use a cheap ext class D amp.
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#494
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If it's anything, it is likely to be the candohm resistor and not the huge 2 section ceramic resistor, as I remember, there was one section of the candohm that was slightly too high (r128 SAMS), and was bypassed, so prob, other parts are starting to go as well.
Of the 3 parts, one is a bit hard to match. R 128-A(6750-ohms) 3.2watts R 128-B(12-ohms) ˝ watts R 128-C(93-ohms) 4 watts what I found to replace. (mouser parts) 594-AC040006801JAC00 756-WP2S-12RJA25 71-NS00593R00BE12 These should be close enough, I would hope!
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