(Topic ID: 234512)

LAH - Crane unlocking relay does not operate

By jimy_speedt

9 months ago

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  • 2 posts
  • 1 Pinsider participating
  • Latest reply 9 months ago by jimy_speedt
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#1 9 months ago


I am repairing this machine which was held in a cellar for some time. Here the relay under the crane arm which releases the ball is not working. I made a specific test in test mode, no way.
I have checked the voltage on both lugs of the relay, when the magnet is not activated. 41Vdc on each.
If I activate the magnet in test mode by pressing the Start button, nothing happens, the voltage on both lugs stay the same.
I then measured the continuity of the drive, from the relay up to the transistor Q43 on the CPU (via the PPB). OK
If I made a test on CN11 - 5, I get stable 41Vdc even when I press the start button in test.
I removed the CPU board and checked both Q43 and the small associated transistor. The resistors on the path to the IC are ok.

Should I think of a failure on the 7408 ? or the 6821 ?

Thanks for the help

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