My CSA803 now passes the Self test and Extended diagnostics test.
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In an earlier message I wrote that some if the 5 IR sensor groups were never selected during a full scan cycle. It appeared that this was due to a faulty 3-to-8 line decoder 74LS138. I replaced this IC and bingo. In hindsight I am not 100% sure that it was the IC itself, or a bad solder joint to one of the 3 input lines. After replacement the operation of this IC was not stable. I resoldered the 3 input pins and that cured the problem. Previously I had checked everything for continuity with an ohmmeter and found no bad joints, but now with a probe I saw that the slightest pressure on the pins or on the board changed the results. The repair time was nothing compared to the total time I spent to find the problem. I nearly completely reconstructed the schematics of the A9 Front Panel Control board and A10 Front Panel board, and the way all circuits are operating. Interesting and "on the fly" I got more insight in the CSA803. Once you know where and what to probe it's fairly simple to detect non-functioning IR pairs. A silly mistake: after resoldering, all horizontal pairs worked well but still a few of the vertical pairs didn't. Then I realized that the distance from IR Led to sensor is much larger for vertical pairs than for horizontal pairs, and I used the bare board -- without the frame of "lenses" which are supposed to concentrate an IR Led light better on the corresponding sensor. With that frame in place all pairs worked fine. On Thu, May 17, 2018 at 02:36 pm, Albert Otten wrote:
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