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I'm trying to startup my Placid and I'm adjusting the pots. VR1 & VR2 adjust fine. VR4 does too (~2K) VR3 is ~10.11K. adjusting the pot will bring that up or down, but it's not gonna get there. If I read across R7, I get ~2K resistance - same as reading across R8. Can anyone suggest other checks I can make, or is this likely a bad pot?
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Any help would be appreciated 
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Brian or Russ, I'm hoping that with you back from vacation I can get some help here. Apologies in advance if this is a 'rookie' issue. If you could give me some tips on how to troubleshoot without power (resistance at various points), or whether it's ok to apply power and troubleshoot 'hot'. Either way, I need some help 
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Could definitely be a bad pot. Sometimes the wiper will warp if you turn the adjustment screw too far.
What I do find odd is that even in the worst case it should still be around the value of the pot. Are you sure there is no other mistake?
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No Russ - not sure. When I remove the pot and read across, I still get VR3 ~10.11K. I suspect it's something else, but I'm not sure what to check, or whether it can be done with/without power. That's where you could be of great help :-)
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Is there somewhere else I should go to try and get some direction/help?
* Would I do harm if I applied power and took some measurements?
* Are there any other points I can check without power that might shed some light on the cause of my problem?
I realize it's probably a bit of an annoyance to work with such a noob, but I'm a bit disappointed that in nine days, I haven't had anyone (company or otherwise) really engage.
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Originally Posted by: MisterRogers  No Russ - not sure. When I remove the pot and read across, I still get VR3 ~10.11K. I suspect it's something else, but I'm not sure what to check, or whether it can be done with/without power. That's where you could be of great help :-) (Sorry, not ignoring, just really busy this week.) Are you saying the pot does not adjust? Measure between the center pin and one of the outer pins.
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Thanks for weighing in Brian. I'll measure as soon as I get home. I pulled the pot - should I measure with the pot in?
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It can be measured in or out.
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it measures 7.87 mOhms from center to outer pad (red on center). The other side measure a touch over 2K ohms. So it's not the pot. where to now?
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If the pot is adjusting correctly, it youare not able to adjust the supply, it points to misplaced transistors. Use the parts list from the web site and double (then triple) check that the transistors are mounted in the correct spots.
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Thanks - I'll do that Brian.
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Ok - checked the transistors (QN2 & QP2), changed them just to be sure. Replaced the pot too. Max I can still get increasing VR3 is ~10.50k I checked QN1/3 & QP1/3. In the board, transistors seem to never pass the diode test. I looked up the data sheet to identify my BEC. None of the 'Q's behave as they do with diode test 'in board' vs. out. So if I know the circuit that VR4 adjusts is correct (I can get it to ~2K), and the Q's measure the same with the VR3 circuit, must be something else - yes?
So what should I check next? I'm suspicious of IC1/2. They came on the board, but when I look at the schematic they look to be be important (in that part of the circuit). Anyway, everything is where it should be, same problem. Next?
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What voltages are you getting? You will not be able to adjust a 10K pot higher than 10K.
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Doh. That's the problem with doing thoughtful work before a couple cups of coffee. Pots are now dialed in. On to applying power. Thanks for your continued help Brian. I'm trying to find a good diagram for wiring up the transformers. Also, I can't find a startup pot adjust description for the LCDPS. Could you help with those?
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Specifically Brian - how should I wire the transformer secondaries to a Placid BP that's gonna drive a Legato 3.1, and how do I trip and wire a LCDPS that's gonna drive the Buffalo II. Getting closer, getting excited :-)
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Cancel that request - she's alive! Hunted down what I needed, cased it up yesterday, and I have a working Buffalo II. Thanks for all your help Brian, she sounds fantastic.
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