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biggsd  
#21 Posted : Wednesday, May 22, 2019 8:55:49 AM(UTC)
biggsd

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Yes, the placid and the legato all through the ground screws?

transformers no, but thats normal.

any other tests i can do on the faulty placid?
Brian Donegan  
#22 Posted : Wednesday, May 22, 2019 12:58:54 PM(UTC)
Brian Donegan

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Do the Placids always fail at a venue, or has it also happened at home?

I am still trying to figure out what could be causing the failures. I have never heard of this type of failure from other users, so there must be some anomaly we can identify (or this has happened elsewhere and I have not heard about it Whistle ).

My current thinking (no pun intended) is that there is a DC voltage (pr something) present on the ground lines of the venue that is causing something strange to happen when you power up there.

.

Edited by user Tuesday, May 28, 2019 2:19:58 PM(UTC)  | Reason: Not specified

biggsd  
#23 Posted : Saturday, June 1, 2019 11:05:42 AM(UTC)
biggsd

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Yes, i have a full test rig now. 2 x desktop power supplies with current limiting.

Spare legato board as a load.

Test rig works and i can definitely test working boards. Tested some old placid 1.0 boards with rig and all test fine. 15v output, 50ma shunt, so my testing platform is all working fine.

I have two failed PLACID 2.1 boards. All faulty on + side.
Board 1: (and was in the most recent fault with blowing rectifier):
15v no load output no problem.
When i add the load, i can maintain 15v BUT only if the shunt current is like 90ma.
As soon as i drop the shunt current using the pot to 50ma, the voltage drops to like 10v.
vref is 2.48 v.

Board 2:
it was behaving as above. But then suddenly it went short circuit
Current limiting input using power supply. had it up to 1a and it still wants more.
I have replaced all of the actives - 7 transistors - including shunt ones - still is showing short circuit.
Could IC1 be a fault?
What should i replace next?

maybe can someone help me with any more tests I can do?

Edited by user Saturday, June 1, 2019 11:06:40 AM(UTC)  | Reason: Not specified

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