#46
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Quote:
Grounding the ABL base will kill the ABL. If the jailbars are getting in there they will go away. You may or may not see other changes without ABL. B+ lines should be clean, sometimes there is a very small amount of hash but nothing like 5% or 10% of voltage. With this problem you have to take things in order. 1) be sure all B+ are clean & correct 2) scope starting with the detected video from IF strip pin 5 3) work your way to the right through video til the waveform goes "bad" thats where it gets in. 73 Zeno |
#47
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...
Last edited by andy; 12-05-2021 at 07:52 PM. |
#48
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Quote:
I've traced the B+ to two different sources. One is from a line from the transformer that is amplified by a diode and then is tapped into the canister. From there it goes to the chroma module and makes it way around the boards. The other B+ comes from another line of the transformer and goes though a resistor and then on to the horizontal board where it connects to the pin right next to where the first B+ connects. It's a loop, but why from different lead of the transformer and why is only one end filtered by the caps? When I get home I'll take a picture of the waveform I mentioned and post it.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
#49
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I'll do that. Guess I misunderstood the need for the 10x. Most of what I read and watch talked about sensitive modern circuits needing the probe. For some reason I don't think of an older television as being that sensitive with all the high voltage and other things going.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
#50
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Okay, here are recent waveforms.
First pic is the ABL base. It measure roughly .75 volts DC and this waveform is the AC with settings of 1 volt/div and 20us time/div. Odd thing is, the AC and DC waveforms are identical. Second pic is the ABL collector's DC waveform. It measured roughly .5 volts DC. The AC looked the same but with settings of 20m volt/div and 20us time/div. The third pic is the B+ 125V with a setting of .5 volt/div, but with the 10x probe the display is 5 volt/div and 5ms time/div. See how fat it is? Every other wave form is a single line except for the B+ 125. Last pic is the B+ 125V again with different settings of 1 volt/div but with the 10x probe the display is 10 volt/div and 10us time/div. The DC showed a flat line at 50 volt/div for roughly 2.5 divisions.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 Last edited by TinCanAlley; 09-30-2013 at 02:50 PM. |
Audiokarma |
#51
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Quote:
a) 1V/div b) 100V/div jr |
#52
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With the probe in the 10x mode it would be 10 volt / div. Isn't that how it works? If I set the scope to 1 volts/div and put the probe in 10x mode, it would reduce/lower/attenuate it by a factor of 10 and the display should be read as 10 volt/div?
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
#53
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Okay, just grounded the ABL's base leg and the jail bars remained. The only affect it had was to brighten the screen when grounded and go back to original brightness when ungrounded. So it seems the ABL circuit isn't to blame.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
#54
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Quote:
So "b" is the correct answer to my question... agree? Now, where do you set the baseline "0 volts" before probing a DC voltage? If probing a positive voltage, I set the baseline to the lowest line on the 'scope face and count divisions up from there after the DC is applied to the probe. If unsure of polarity, I set the baseline (with no voltage applied) to the center graticule line and see which way the trace goes when probing the voltage. jr |
#55
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For the DC I put set it to GND and moved the trace to the bottom of the screen and then switched to DC. It moved up as it was positive. Since the DC was showing a waveform, I moved the baseline to the top of the first division so it would show the entire waveform.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
Audiokarma |
#56
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Quote:
jr |
#57
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I just scoped all of the B+ 125V to and from each of the modules. It was consistent throughout, if I thinned out the waveform, it was roughly 1 VPP before it lost the trigger. If you count the fat wavefrom, it would be roughly 3.5 VPP. So I'm pretty sure 1 VPP of ringing isn't going to create the jail bars. That and I've pretty much ruled out the ABL. Not sure where check next. I've done the horizontal oscillator, wave generator and output on the horizontal board. I don't have the probe necessary to do anything with the FB, yoke or HOT.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
#58
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Without knowing the specs. for the 125V supply, it would *seem* to me that 3.5 volts of garbage would be more than I would like to see. Perhaps there are some filter caps in the 125V supply that are not functioning properly.
jr |
#59
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Yes C-1 is Zeniths term for composite video. Some sets
even have a "C-1 adjust" pot. Grounding the ABL base proves its NOT coming from there so ignore all between the ABL base & tripler. Depending on the scope I was using I almost never used DC only AC since I was looking at waveforms. On my sencore there was a built in meter to speed things up. Also be sure all your calibrations are set. The are the red knobs are set to "cal". Some have an arrow to show which direction to turn them. If the scope is dual trace you can use sync on B to stablize the waveform. Hook the B channel probe to a clean hoz signal such as the hoz drive collector, this may get rid of the multiple traces. 73 Zeno |
#60
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Okay, moved on the 240V boost section. I'm attaching three waveforms. Each are done at 50V/div and 20us/div.
The first is directly from the lead off the flyback where it connects to the boost diode. It's taller than my scope can display. I didn't realize it was 900V. Glad my scope didn't do something bad. I'm growing fond of it. The second is on the other side of the boost diode and is now 248V. The waveform covers just over two divisions, so it's just over 100V and there's ringing in it. The third is through a resistor and to the 10uf 300V capacitor. Again, I'm getting a really crappy waveform, but the basic form is the same as pic 2. Now I tried scoping the other 240V boost, but I couldn't get a meaningful waveform. Where I scoped for pic two, it splits off from there to another point where it's connected to a 15ohm coil. It measures at 248V, but the waveform is pretty much non-existent. Don't know if it's the coil smoothing it out, or if my settings aren't working for it.
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Pioneer SX-1080, Pioneer PL-115D, Pioneer CT-F9191, Pioneer RG-1, Wollensak 8050A, Akai 4000DS MkII, Pioneer CS-05 & Polk 1.2TL Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650 |
Audiokarma |
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