I had a couple of 60in1's on the bench tonight, one which had very low audio volume which would decrease over time until you couldn't hear anything and the audio amp heatsink was getting extremely hot and the other board had no sync.
No Audio:
At first I suspected the amp was faulty and swapped it out with a known good one which made no difference.
I had another 60in1 which had a sync issues so I had a look at the voltages on both boards and compared the two.
The dodgy board had it's output being dragged down so I started with the audio caps.
I pulled the two 470uF through hole caps at the bottom corner of the board next to the amp and ran them through the cap tester with two significantly different results.
Good but not great for a 470uF cap...
Faulty cap of the same value...
I replaced the bad one (circled in red) and audio was restored.
No Sync:
You could see there was video on screen and audio was good.
The sync signal was missing when checked on the scope.
I traced it back from the edge connector and it ends up at the output pin 2 on an LV244A buffer at U8 (circled in red).
There was a good signal on the input (pin 18) so I swapped it out and video was restored.
This was my first time repairing these and both were relatively easy fixes, it was my second time swapping out SMD chips and fortunately all went smoothly.
Question
Kaizen
I had a couple of 60in1's on the bench tonight, one which had very low audio volume which would decrease over time until you couldn't hear anything and the audio amp heatsink was getting extremely hot and the other board had no sync.
No Audio:
At first I suspected the amp was faulty and swapped it out with a known good one which made no difference.
I had another 60in1 which had a sync issues so I had a look at the voltages on both boards and compared the two.
The dodgy board had it's output being dragged down so I started with the audio caps.
I pulled the two 470uF through hole caps at the bottom corner of the board next to the amp and ran them through the cap tester with two significantly different results.
Good but not great for a 470uF cap...
Faulty cap of the same value...
I replaced the bad one (circled in red) and audio was restored.
No Sync:
You could see there was video on screen and audio was good.
The sync signal was missing when checked on the scope.
I traced it back from the edge connector and it ends up at the output pin 2 on an LV244A buffer at U8 (circled in red).
There was a good signal on the input (pin 18) so I swapped it out and video was restored.
This was my first time repairing these and both were relatively easy fixes, it was my second time swapping out SMD chips and fortunately all went smoothly.
Edited by KaizenLink to comment
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