(Topic ID: 273148)

Williams Type 2 Sound Board has 5V Short - How to find?

By minnesota13

3 years ago



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    #1 3 years ago

    Working on a Baracora I found no 5VDC on the Sound Board Test point. I noted that the 7805 was hot. I removed the 7805 and measured 1.4 ohms between +5VDC and Ground indicating a short somewhere on the board.

    Almost all electrolytic caps have been replaced with orientation triple checked. I Checked all of the little glass caps with a magnifying glass and none looked burned or different from one another.

    What are the possible shorted devices that would be high on the list to lift their 5V supply line?

    #3 3 years ago

    Thanks for the reponse and video. I tried the technique, but my meter doesn't have the lower resistance capability. I went through all of the newly replaced capacitors with a close look on the wiring side. I found a tiny solder splash that didn't look connected between the capacitor and a nearby trace as the trace was covered with the original solder mask. I removed the splash and the short was gone.

    I replaced the 7805 with a 2A 78S05 regulator and the sound board is now working. A self induced problem solved. I've got to look a lot closer after replacing components.

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