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  #16  
Old 06-29-2011, 12:32 AM
ctc17 ctc17 is offline
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gassy or weak HV rectifier. 3A3. Change it, dont test it
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  #17  
Old 06-29-2011, 06:01 AM
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tried 2 3a3 and 3 6bk4 and a damper. i think this all has to do with the fact that the hv pot will not adjust the hv at all. i dont find anything stressed or burned and when i had it on, the flyback ran only warm not hot at all. its all ????? at this point.
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  #18  
Old 06-29-2011, 09:25 AM
DaveWM DaveWM is offline
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did you ever check the voltage drop across the 1k resistor in the shunt tube cathode circuit. should be between .5v and 1.5v.

there is not much too the HV regulation, the pot, a 1.5meg to ground IIRC and a .01 HV disc cap. IF that voltage drop across that 1k resistor is too high then the HV regulation is clamping down to hard.
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  #19  
Old 06-29-2011, 09:29 AM
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could it be a bad 6dq5 hot? since this one gives 24kv bright down but i tried another one and it gave 30kv and i think the bright was half down because there was arcing going on, 30kv is to much and ill have to try the hv pot again with the tube that is showing 30kv and see if it adjusts down at this point.
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  #20  
Old 06-29-2011, 11:18 AM
ctc17 ctc17 is offline
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Yes, use the strongest 6DQ5 with the strongest output then figure out why the regulator isnt holding the voltage down.


The test Dave and I are suggesting were simple standard diagnostic tests for tube color tvs. You are making things very hard and wasting lots of time by not doing these tests.
The voltage accross the 1kΩ resistor would have told us this like 3 days ago
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  #21  
Old 06-29-2011, 11:57 AM
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where is this 1k resistor? if theother tube is putting that much more out then its possible that the pot will work as i dont think i tried it when i used that tube and the pot is at alittle over half the way up.

Last edited by timmy; 06-29-2011 at 12:00 PM.
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  #22  
Old 06-29-2011, 12:34 PM
DaveWM DaveWM is offline
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trace the shunt tube cathode, it goes to the 1k. You need to make sure its not drifted, should be a 5%. the 1k needs to be accurate to determine the current in the shunt, as its the voltage drop accross that. I generally just hookup a multimeter on both sides, take a resistance reading (before powering up the set) should be 1k, then switch to voltage and power up, you should see .5 to 1.5 depending on how the shunt in working (tapping off excessive voltage on dark scenes, the v drop will be the highest showing current flowing thru the 6bk4, bright scene the voltage drop will be much less, around 200-500mv. The idea here is to determine if the lack of HV is due to a the HOT/Fly or the shunt. if the shunt current is low in a dark scene then it mean the HOT/FLY is not puttting out enough HV to start with (so you check that there) if the shunt is clamping down hard even in bright scenes, then the HOT/FLY is prob ok and the shunt circuit needs attention.

You need to narrow down the problem, or you could get lucky and just keep replacing parts hoping to find the problem.

Obviously the 1st thing to check when you have HV issues is the big 4

HOT/HV rec/damper/shunt.

you can just sub those with know working tubes and if that fixes the problem start replacing one tube at a time with the orig. The problem with this approach is you may or may not have good tubes to sub with, SO you need to think the problem thru and apply what the test that have been described.

Besides all this you really should setup the HV that means the the the eff coil and the HV while checkng the HOT and Shunt currents (as has been described several times already), skipping this (just replacing tubes and adj the HV) can result in unnessary stress to a flyback that can result in damage of a part that can be VERY hard to find.
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  #23  
Old 06-29-2011, 12:56 PM
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where is this 1k resistor, forgive but i know the basics and im sure you guys are doing this alot longer then i ever will,lol,lol. when i first got the set i could not get hv because someone put the jumper in to check milli amps but never took the jumper off until i found it and removed it so i assumed the current was set because the fly was replaced and it runs just warm not hot.

Last edited by timmy; 06-29-2011 at 01:06 PM.
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  #24  
Old 06-29-2011, 01:03 PM
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I am not sure but if you look on the bottom of the chassis, you will see a 1k resistor right off the shunt tube socket pin, I dont think is mounted to a pcb.
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  #25  
Old 06-29-2011, 01:05 PM
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sams may call out a test point that would be easier to find, it would be in the HV setup instructions.
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  #26  
Old 06-29-2011, 01:07 PM
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shunt tube would be the 6bk4? or the resistor directly under the 6cg7 tube and measures 170.8k

Last edited by timmy; 06-29-2011 at 01:15 PM.
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  #27  
Old 06-29-2011, 01:39 PM
DaveWM DaveWM is offline
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Pin 1 of the 6bk4 there should be a 1k resistor, it may or may not be directly attached to the pin socket, but if not you should find a wire that goes from pin 1 to a 1k resistor.
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  #28  
Old 06-29-2011, 01:45 PM
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i did not find a 1k and this chassis i believe is a clone if this makes a diff.
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  #29  
Old 06-29-2011, 01:50 PM
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pin 1 is yellow and goes to a terminal block from there its soldered to a 1kv ciramic cap them goes to resistors for the hv pot but they are not 1 k the sams says its 1.5 meg, there are 2 of them.
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  #30  
Old 06-29-2011, 02:12 PM
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do you have a sams on this? if so check the schematic, if it shows the 1k then it should call out the ressistor and then you should be able to find it on the componet location pics.
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