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My recent BIII dual mono build with two Legatos is causing me problems. I power up Saturday and only get 1.8- neg volts on the recently built Legato board. I tap on the relay and get the full -14.8v. Pos side gets full power every start up. I went over all the solder joints and still have to tap on it to get full voltage. Last night, my old reliable Legato (born Feb 2012) from the single build started having the same issue; only 2.0v on the pos side until I tap it. The neg side gets full power every time it starts up. I've also tried disconnecting the outputs, no change. The two Placid HD BP’s are shunting 50mA on the pos and neg side, running at 14.85v on the + and - all warmed up. All grounds test good powered with voltage drop test and ohm out well unpowered. No change connecting power supplies direct to the Legatos (not using the one point ground for all grounds); still have to tap the relay. Any ideas on what I am missing?  Edited by user Tuesday, September 11, 2012 12:04:05 AM(UTC)
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Try shunting a little more than the 50mA. Make it a 100mA just for the test and keep an eye (or finger) on the heat sinks - don't let it overheat.
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The relay is not switching power, so it should not have any effect on the rail voltage. It switches the SE output signals.
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Well, if not supplied properly it certainly won't click. The cut-in power requirement could be higher than the steady state requirement. That's why I suggested the increase in shunted current. Edited by user Tuesday, September 11, 2012 3:32:41 PM(UTC)
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 1 user thanked avr300 for this useful post.
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Thanks avr, that seems to do it. |
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