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Sansui AU-G77XII display bulb issue
Sansui AU-G77XII display bulb issue
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Old 14th October 2021, 02:45 AM   #1
jhouse55 is offline jhouse55  United States
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Default Sansui AU-G77XII display bulb issue

Hello, I have had this AU-G77XII unit for a while and decided to buy a new bulb for the display panel (shown) which is board 5504 in schematic. When I measure at the bulb while itís on there is no voltage so then I questioned if even the bulb is bad. Looking at the wiring diagram, this board connects to the display board pins 84 and 56. That then connects from the display board back to the power supply board where it says 12v. If in the event I check the voltages back to the power supply connection and itís no voltage there either, what would supply that voltage? Iím wondering if there is a bad solder joint causing this. The picture of the working unit is just a example. I can see the meter lights moving with the music when I look at it closely, itís just not lit up due to the bulb not working.
Thanks in advance for any help.
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Old 14th October 2021, 05:43 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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56 is ground and 84 comes from the regulator m06 which is fed from the 20volt supply through mR11.
Which point is not correct; 20v, regulating transistor or mR11?
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Old 14th October 2021, 11:04 AM   #3
jhouse55 is offline jhouse55  United States
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Thanks so much, I will check out that regulator (2SD1061) and the 4.7k 1/2 watt resistor once I get back home later. I suspect if I only have a 1 watt resistor, just wait to get the 1/2 watt version?




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Originally Posted by JonSnell Electronic View Post
56 is ground and 84 comes from the regulator m06 which is fed from the 20volt supply through mR11.
Which point is not correct; 20v, regulating transistor or mR11?
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Old 14th October 2021, 11:21 AM   #4
MikePP is offline MikePP
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mr11 is 4r7 not 4k7 !!


It's effectively a fuse for that circuit.
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Old 14th October 2021, 11:24 AM   #5
jhouse55 is offline jhouse55  United States
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My bad
Thanks Mike!


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Originally Posted by MikePP View Post
mr11 is 4r7 not 4k7 !!


It's effectively a fuse for that circuit.
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