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I assembled the Placid PS kit for Buffalo II and connected to a 9V 15VA transformer but the LEDs are not glowing. The kit does not come with 2 x 1 ohm resistors therefore I soldered a 0.5 ohm resistor instead. I can adjust the output to 5.5V but I cannot adjust the R8 to 0.74V. I connected the PS to Buffalo and the Buffalo is not working. Is there anywhere I should check for this failure?
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With a resistor half the value, you'll need half the voltage, for the same current, not double.
It's very strange that the LEDs aren't coming on. sure they aren't in backwards?
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If the +ve is the longer lead, then I'm sure the polar position is correct.
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i have heard mentioned earlier that the led lights have a flat surface on the bottom side , therefore that is the position that they should go on the pcb .
regards
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What do you mean "flat surface on the bottom"? Do all LEDs have flat surface on the bottom?
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Hey men, I can't read oracles.
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There is a notch on the rim of the LED ,and and there a part of that rim that is flat , The Placid has the same drawing on it , as seen when you look at D1 and D2 .i will try to upload a pic showing that . regards regis attached the following image(s):  2010-09-13_171702.jpg (72kb) downloaded 248 time(s).You cannot view/download attachments. Try to login or register.
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Ah, I see what you mean now. Yes, I follow this direction to install the LEDs. Is there anywhere I should check & measure the voltage and report?
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You could measure voltage across D1 and D2.
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Here are some of the measures Voltage across D1 & D2 to GND = 12.5V IC1 Pin2 5.62V Pin3 6.5V Regulator Output 5.62V Voltage after rectification (C1) 12.9V R3 and R8, no voltage detected VR1 48 ohms VR2 615 ohms Edited by user Tuesday, September 14, 2010 4:53:06 AM(UTC)
| Reason: Not specified
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I mean across D1 and D2, not to GND. One probe on each of the pins of the LED. Edited by user Tuesday, September 14, 2010 9:00:20 AM(UTC)
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Oh I see, D1 is 2.5V and D2 is 0.5V
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Hmmm, something is definitely wrong then. They should both be about ~1.9V Double check you have not accidentally transposed parts.
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There are only a few parts and I have double checked everything. Other than the missing 1 ohm resistors that I use 0.5 ohm instead, there is nothing wrongly inserted. However, I found the IC that came with the PCB is L49710 instead of OPA227 as specified on the parts list. Is this a concern?
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Is the IC correct? Any clue to rescue this?
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Yes, that it the correct chip. I think I need to update the parts list.
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Then where to look at for possible fault?
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Can you post pictures, top and bottom of the board?
I am still thinking a pair of transistors is swapped.
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Here are the photos. I have also inserted the 1 ohm to the PCB. Edited by user Saturday, September 18, 2010 8:00:39 PM(UTC)
| Reason: Not specified sunchan attached the following image(s): Top.JPG (173kb) downloaded 112 time(s). Jfet position.JPG (114kb) downloaded 112 time(s). Bottom.jpg (180kb) downloaded 111 time(s).You cannot view/download attachments. Try to login or register.
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