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LJ
Joined: 09 Dec 2008
Posts: 47
Location: Earth
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 Posted: Mon Feb 02, 2009 7:08 pm Post subject: |
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Try again,
1. What is the voltage at C815, C816, C820, collector Q803, emitter Q806 and cathode D803 ( TLP721FD4GR ) when on position?
2. What is the voltage at C815, C816, C820, collector Q803, emitter Q806 and cathode D803 ( TLP721FD4GR ) when off position?
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| Posted: Tue Feb 03, 2009 3:27 pm Post subject: |
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Still trying to isolate the fault.
During "ON" stage During "Off"stage
C815 - 142.3volt , 142.3 volt
C816 - 10.00 volt , 9.82 volt
C820 - 11.76 volt , 8.93 volt
Collector Q803 - 83.9 volt , 83.9 volt
Emitter Q806 - 1.8volt , 0.77 volt
Cathode D803 - 76.7volt , 76.7 volt
When I use external source to power the +15 volt rail (tv set off)IC 805,806,807 is working perfectly.IC1102 and IC601 are running you can scope the horiz drive at IC601 pin 19. Even the IC1102(MPU) is working you can enter data thru channel UP/Down and monitor on the scope
I really dont understand why the voltage is being pulldown, +15 volt rail is not supplying enough current to the regulators?Voltage at C816 should be 18 volt without load? |
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LJ
Joined: 09 Dec 2008
Posts: 47
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| Posted: Tue Feb 03, 2009 6:13 pm Post subject: |
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Check for Q803, is it ok? also check for C820, R828, D820 (MA4360L / 36V zenner), D819 (MA4100M / 10V zenner), D830 (MA4020 / 1.88V zenner) and D803 (photo coupler) are they ok too?
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jts1957
Joined: 24 Nov 2008
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| Posted: Tue Feb 03, 2009 7:13 pm Post subject: |
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| I'd like to know how photo coupler in feedback loop, (if defective), would be having a bad effect on ONLY ONE of the secondary voltages? |
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jts1957
Joined: 24 Nov 2008
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| Posted: Tue Feb 03, 2009 7:20 pm Post subject: |
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| If you have Horizontal drive out of the Jungle IC, what about at Q502 base / collector (driver) & Q501 base / collector (if your scope can handle it)(Output)? |
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Jujeet
Joined: 25 Mar 2007
Posts: 22
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| Posted: Wed Feb 04, 2009 3:48 pm Post subject: |
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I have checked all the components as mentioned .Everything is OK.I notice Q802 should turn on to provide +13 at collector of Q802.This is happening without 0.6volt across base and emitter of Q802. Turn on bias occur when you initially on the set.Q806 base must be in high state for Q803 to work. Q806 base is controlled by MPU.
I can only scope the horizontal waveform till the base of Q502 , I am using external source. I dont have the 142 volt (Tv is Off state)
Best Regards |
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jts1957
Joined: 24 Nov 2008
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| Posted: Wed Feb 04, 2009 7:42 pm Post subject: |
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| Since you like to use external sources, (and post that fact only later on), have you tried forcing Q806 turn on? |
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LJ
Joined: 09 Dec 2008
Posts: 47
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| Posted: Sat Feb 07, 2009 8:00 pm Post subject: |
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| jts1957 wrote: | | I'd like to know how photo coupler in feedback loop, (if defective), would be having a bad effect on ONLY ONE of the secondary voltages? |
I don't mean that photo coupler in feedback loop having bad effect on ONLY ONE secondary output, i just want to make sure if the st-by system ok, in this case i see maybe the st-by system is failure.
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LJ
Joined: 09 Dec 2008
Posts: 47
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| Posted: Sat Feb 07, 2009 8:18 pm Post subject: |
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| Jujeet wrote: | I have checked all the components as mentioned .Everything is OK.I notice Q802 should turn on to provide +13 at collector of Q802.This is happening without 0.6volt across base and emitter of Q802. Turn on bias occur when you initially on the set.Q806 base must be in high state for Q803 to work. Q806 base is controlled by MPU.
I can only scope the horizontal waveform till the base of Q502 , I am using external source. I dont have the 142 volt (Tv is Off state)
Best Regards |
That what i mean, base Q803 voltage come from D830, if D830 is a 1.88V zenner and emiter to base Q803 bias is 0.6V - 0.7V, at least there's 2.something at D830 cathode to make Q803 work.
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jts1957
Joined: 24 Nov 2008
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| Posted: Sat Feb 07, 2009 9:40 pm Post subject: |
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| D830 is 2 volt zener diode. |
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