#1
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Packard Bell Roundie
this one started out well, just a bad doubler cap, (a previous repair included a new doubler cap that was also bad) a couple weak/shorted tube. Raster comes up and tuner works (audio and no sync video).
Sync sep tube and AGC were the 1st things checked, no joy. scoping around proved the sync pulses were full of video noise (both horz and vert sync not good). The problem ended up being twofold, an open plate load resistor in the sync separater tube, AND a badly drifted resistor that couples a horz pulse the the noise inverter tube from the focus coil. Built like a zenith, all tube, no PCB's, but uses the 6Gu7s in the chroma board like an RCA and a 12AZ7 for the demodulator. Also uses a 6Bk4 shunt tube, which I like more than the Zenith pulse type 6HS5's (I seem to have more trouble with those than the shunt tubes). It also uses a focus tube and not a Se stick Anyway working very well, but still has a bit of noise in the pic, I tried a new RF amp and osc tube, as well as cleaning the tuner. its not bad, but its there. Sometimes I wonder if is just my crappy cables, or maybe a bad balun. would be nice if I could just bypass that and go directly to the tuner with a 75 ohm coax. |
#2
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oh and its got a real funky degausser circuit. Its manual (push button on rear of set). Does not seem to work.
whats odd is on my later PB the circuit makes use of line AC in series with the coil, and a charging circuit for a large electrolytic cap. pushing the button starts the charging process which draws AC thru the degaussing coil. As the cap charges up, the current thru the system drops. releasing the button cuts off the now minimal current flow (fully charged cap) and also starts to discharge the cap thru a resistor. I guess you could mess it up if you just popped the push button very quickly (did not allow the cap to fully charge) but it only take a couple seconds. Now that is the later version. this set is different. it uses a large NP cap about 4uf and B+ (410 right off the doubler) and a couple resistors and a single diode (the later one described above had a full wave bridge). I cant for the life of me see how it would generate an AC thru the coil (the 410 is before the choke so it has some ripple on it but not much. and it does not seem to work (press the button and you can hear a tiny bit of coil noise, but it does nothing to the pic. |
#3
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you think that convergence board is big enough
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#4
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So big that it should have brail labeling on it so the blind, whom it was clearly built for, can preform the the convergence procedure without memorizing the control locations.
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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 |
#5
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I remember seeing that one. That is a rare set, I doubt they made very many. 99C1 chassis. Looks like they tried to combine the best of zenith and rca together, a selectively breed set
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Audiokarma |
#6
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It sure looks like it can handle a lot more tweaking of controls than a typical open-board one.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
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