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#1
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Are these things I should consider bad
I've noticed a few things that I'm not sure about. I've posted pics.
The first is the damper on the HOT. The leads look like they've encountered a decent amount of heat. The leads are no longer silver. The same goes for the zener diode in the ABL circuit. All other diodes in the set have silver leads with no signs of discoloration. The last one is a composite resistor in the ABL circuit. I don't know if this is a defect in manufacturing or if it's heat damage. Could be someone touched it with an iron. Thanks.
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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 |
#2
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Don't know aobut the resistor. If you know the correct value, you could measure it, or just replace it as a matter of course.
If those diodes have actual silvered leads, it is normal for them to tarnish over time. Any actual heat damage would likely cause a failure, so if working, leave well enough alone. |
#3
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I have the NOS zener and the resistors will be here on Saturday. I'm just going to replace them all and see if it helps.
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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 |
#4
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You can rest assured that a damper diode either works or fails - there is no in-between. If it fails, the horizontal sweep doesn't work and you probably will blow a fuse. So, if your set is basically working and your complaint is those jail bars, it's not the damper diode. The zener, on the other hand, could fail open and the effect on operation might not be so obvious.
There are a couple of ways to check the Zener in operation. One is to measure the DC voltage across it and see if it is correct. This presumes that the Zener is conducting during normal circuit operation. But sometimes, a Zener is used in a circuit for over-voltage protection, and then it only conducts if there is a fault; in this case the voltage could be anything less than the specified value. You can also check with a scope, but this is more complicated unless one end of the zener is grounded, because you have to check both ends and subtract one from the other to see if the voltage difference is constant and equal to the correct value. |
#5
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http://videokarma.org/showpost.php?p...22&postcount=3 The schematic of the tripler with the brightness limiter and zener makes my head spin. If I'm reading it correctly, the zener is connected to the ground of the tripler and chassis ground. There's also a spark gap going across those two points. I can't seem to figure out how the zener gets its 7.5V for operation connected to two grounds.
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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 |
#6
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I don't know if the Zener is supposed to be always regulating at 7.5 volts, or just limiting the voltage to 7.5 volts if it tries to go higher. You can find out by measuring the voltage from the top of the Zener to ground (or scoping the top) to see if it is 7.5 volts, or if it is less. |
#7
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I've attached a pic of the underside. I've circled the connections in question. In the left circle is the black wire which connects to the 500ohm resistor on the tripler ground, the white/green wire to the brightness limiter pot's T1, one leg of the zener and one leg of the spark gap. The right circle is a ground point (soldered to the chassis' top side) that contains the other leg of the zener and spark gap. I'm hoping you can understand why I see nothing but grounds and no voltage for the zener.
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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 |
#8
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...
Last edited by andy; 12-05-2021 at 07:52 PM. |
#9
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I will put on the safety cover on the probe and let the plastic rest on the HOT to see if I can get a signal. I'll do the same for yoke and yoke wires. Now the base of the HOT get the horizontal pulse from the horizontal board. I checked all those points on the horizontal board and they matched the waveforms given. The HOT's signal on the base has to go through the horizontal transformer. I haven't scoped the base of the HOT, so maybe that should be next. Maybe there's a problem with the transformer. The SM does show a waveform for the base of the HOT. It says it should be 7V.
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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 |
#10
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So what would you suggest next?
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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 |
#11
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If I put the probe anywhere around the flyback, I get the same as in the focus picture in the previous post. Lots of ringing. Of course I don't know if that's just because I'm not making electrical contact and just picking up on the radiating signal.
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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 |
#12
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I scoped the leg of the diode that connects to the 500ohm resistor that feeds the wiper of the ABL pot, blah, blah, blah. This is what I got. It's an ugly waveform, that's for sure, but what does it mean? It was with a volts/div of .2 and a time/div of 20us.
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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; 09-27-2013 at 09:17 PM. |
#13
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It is really difficult to follow what is going on with the schematic incomplete and in a different thread.
Can you post a bigger chunk, so we see where the ABL signal from the pot wiper goes? Somewhere into the video amps, I assume. Scope the B+ voltage that feeds the video amps, and look for ripple/ringing there. Check the zener diode using the diode check on a DMM as a first go. That will conclusively check for opens/shorts. I'm betting it is still good though. Im thinking you might have a bad bypass cap in the video amp somewhere. |
#14
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I can't tell much from the fuzzy picture, but I suspect that the "ground" terminal of the tripler is connected to ground only through the 500 ohm resistor and series zener diode as well as the pot and 10 ohm resistor.
Even if the 500 ohm resistor were connected *directly* to ground that would not short out the diode, as there can be a voltage drop across the resistor if current is passed through it. Do an ohms law calculation and you can determine how much current is needed to raise the voltage to the zener voltage. jr Last edited by jr_tech; 09-27-2013 at 04:36 PM. Reason: add detail |
#15
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The reason I'm going though all this that I am not an expert in electronics and am still learning. Until I can understand how all these connections can work when they all seem to go to ground and not one of them seems to have any connection to a power source. If I can understand where the voltage for the diode and transistor bias is coming from, it will help me greatly. Is there voltage on the ground terminal of the tripler?
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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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