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Hi,
I've built up my Placid HD and Placid HD BP kits and have run into problems - unable to adjust output voltage.
I checked over my boards to see if I have swapped transistors by mistake and found that I have BC550C transistors rather than BC550B (as per BOM). I have a fully working neg rail on the placid BP HD and this has the correct BC550B transistors. Should I conclude that the 550C's might be the problem?
Thanks
Andrew
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The BC5x0c are fine. They are what I ship for all kits now. I will update the BOM.
Are QN1 and QN2 correct?
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Rank: Member
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Hi Brian, QN1 and QN2 on Placid HD and HD BP are FJ5200 (I was sent replacements as they were originally incorrect) All trim pots are set as per manual (500 ohms and 1K) All LED's are lit. I get the following readings around the boards. Placid HDAC in = 11 volts TP- VN+ TP_CSS = 0v TP VREF = 3.89v TP out - TP shunt = .001v GND and + = 4.28v Placid HD BPPositive rail AC in = 18.2v TP- VN+ TP_CSS = .018v TP VREF = 3.9v TP out - TP shunt = .018 (can adjust to .50 easily) GND and + = 1.055 (no adjustment until current is high) The negative rail is working perfectly. Some pictures to follow. Thanks Andrew Edited by user Friday, March 22, 2013 4:45:41 PM(UTC)
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Rank: Member
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I've re-checked the label on the QN1 and QN2 transistors, they have the following part number written on them: F1A07AA
J5200
0I'm assuming this is correct? I've also re-checked the BC550 and BC560 transistors and gone over the board with solder again checking for dry joints. Still not working on the positive rail of Placid BP and Placid. Neg rail on Placid BP is working fine. Now at a bit of a loss as to what to do. Should I try swapping out some components, and if so where to start? Thanks Andrew Edited by user Tuesday, March 26, 2013 7:01:51 PM(UTC)
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Hi Brian,
Yes, all the Led's are lit.
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All the Led's are lit, what does this tell me (ie what's working)? Ref voltage is at 3.89 volts. The trim pots all seem to work fine when the power is off measuring Ohms on test points. Should I start by swapping out the bc550 and bc560 transistors? I'm unable to adjust voltage up from 1.5 volts on the Placid BP, current adjustment works fine. On placid HD voltage is stuck at 4.25 and current will not adjust (reads 0v across CCS). Any suggestions, I would be most grateful. Thanks Andrew Edited by user Wednesday, March 27, 2013 11:18:33 AM(UTC)
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I have had the same problem.
I am still not shure what causes this, but I suspect there was a shorted joint between QP 9 and R-4. Order a new Placid and took my time when soldering with special attention on the places where the QP and QN transistors where close to The Resistors. On Placid it's four of them, and two on Placid HD.
My new Placid works like a dream.
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Update: I re-flowed the solder on both boards. Some progress - Placid BP is now working. Still no luck with single Placid. Output voltage stuck at 4.2. All the LED's are lit, voltage ref is 3.85, but no CCS current measuring. I also noticed that both heat sinks are cold. I will try replacing the small QP and QN transistors first, then perhaps VR1 and VR2. Anything else I can try? Edited by user Sunday, April 7, 2013 8:13:30 PM(UTC)
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Update: Swapped out all of the BC560 transistors on the Placid HD - all seems to be working now  Edited by user Tuesday, April 23, 2013 9:30:40 PM(UTC)
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