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#1
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Ideally, the B+ has no waveform at all, just a flat line of constant DC voltage. Practically, there will always be a small amount of time variation due to incomplete filtering out of the AC source (unless the device is battery powered). Even if the device is battery powered, there can be small variations due to varying load current drawn by the circuits that use the B+ supply.
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#2
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Quote:
If I see ringing on the base of a transistor, do I look at the collector to see if the ringing has been amplified? Also, I seem to recall someone suggesting I ground the base of the ABL transistor to see if the jail bars go away. The voltage on the base is under 1V, so is it okay to ground it? Doing so won't short anything out?
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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 |
#3
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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 |
#4
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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 |
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