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I just installed an new IEC inlet, power transformer and 2 new chokes. Very exciting.The VDC coming out of the power transformer and rectifier tube appears to be correct. I have an LCLC power supply design. Same as I have been using all along. The VDC going into the first choke is 380VDC and coming out of that same choke is 380VDC. Then the voltage goes into the first cap (40uF) and comes out at 152VDC. Why does this drop occur? Does not seem correct.
Same thing happens at the 2nd cap (50uF). The voltage going into the 2nd choke and 2nd cap is 152VDC, but coming out of the 2nd cap is -17VDC. Something is wrong here.
Any thoughts?
SOLVED: One of the wires for C1 was incorrectly wired directly to L2 instead of ground.
Thank you to all who helped, especially RPMac who noticed the issue.
Edits: 01/29/17Follow Ups:
First, let's confirm your measurements. How did you measure the voltage?As you know, when we measure voltage we are actually measuring the relative voltage between points; we are not measuring an absolute voltage per se. In your measurements, we assume you are measuring one point (e.g. choke in with one probe) relative to a 0v ground reference (other probe). To clear up any misunderstanding on our part, it would be helpful to know specifically at what points in the circuit you took each of he five measurements - two points for each measurement.
For example, where precisely did you take the measurements for the output side of the first choke: from a terminal/wire from the choke to what 0v signal ground point?.. or did you measure from the +ve to the -ve of C1?.. or some other location?
A few other things: Could you also measure the voltage of the PS after C3? Does the circuit include bleeder/voltage divider resistors that are not shown - what are their values.
Once we have this information, the big technical brains here should move ahead quickly with troubleshooting.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 01/29/17
The drawing shows both 380V and 152V at the top of C1. Can you post corrected measurements?
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Buy Chinese. Bury freedom.
The out of L1,the in of L2, and the top of C1 are the same point schematically.
If you are getting two different voltages, they aren't the same point.
Check your wiring and soldering.
Looking at the drawing it seems that you are correct. The voltages at that point should all be the same so either he is measuring incorrectly or there is something else going on. The point of L1,L2 and C1 are all tied together.
Yes, which is why I'd have liked to have known the exact measurement points.
Still, it looks like the OP is on top of it now.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Where do you see a post that indicates Banpuku has resolved his issues?
I am rather curious myself, although it seems either the voltage measurements are not all wrt ground potential and therefore cannot be compared to one another or that one or more parts is faulty.EDIT: OK, so I see that in response to RPMac's point about checking the wiring, etc, Banpuku responded "you nailed it". I'd still like to know specifics; one can learn from these sorts of glitches.
Edits: 01/30/17
Lew,
I agree. It is nice to see when the resolution is posted. It was RPMac that got me thinking about my C1 and C2 caps not being wired correctly.
Specifically, C1 was not grounded, rather it was wired to the L2. And, L2 was not wired to L1/C1 joint, as it was wired to the C1 leg that should have been wired to ground.
RPMac made the salient observation that L1, C1 and L2 all joined together at one common point.
Pat
Thanks for the more complete explanation. Makes sense.
And thanks to RPMac for his impeccable logic.
You give me too much credit. The big help was having the schematic to look at.
If more people would put up a schematic, it would make it easier to understand what is being talked about and easier to learn for us that need to.
I always print out a schematic when I working on a project. Even when building a kit with excellent instructions like Doc B and the BottleHead gang provide.
You nailed the issue. Thanks for helping!
Some circuit or device is passing significant current, to lose that much voltage. Check for leaking power supply caps, which would measure AC Volts. If you remove the tubes, do voltages normalize ? Check the tubes on a tester for shorts. Check the wiring for shorts....
Narrow down the culprit via troubleshooting techniques. Half the voltage means double the current....
~!
The Mind has No Firewall~ U.S. Army War College.
Your choke (L1) has a DC resistance so there should be a voltage drop across it = IR. Since V = 0 then either current is zero or resistance is zero implying a dead short across the choke or that the current is zero(unlikely).
Are you using the DC link caps with the four lead Kelvin connection? If so, make sure you have them connected correctly. That could explain why you are measuring different voltages at the same circuit node. No voltage drop across the first choke suggests no current flowing though it. Other measurements suggest there must be a current draw. Either your choke is shorted or there is a wiring error.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Looking at your schematic, I would disconnect the two 15K resistors and the ASC caps and take your readings. If there is still a great drop my suspicions would be in the Wima caps. But if they are connected to the rest of the circuit I would disconnect that first.
There has to be a short somewhere. If you are testing this with a load, disconnect the load and take your voltages. With no current draw there should be no voltage drop across anything and if there is it should almost be insignificant. Also, make sure your caps are oriented properly(positive to B+/negative to ground) unless you are using non-polarized caps. Then it doesn't matter. But I'm sure if they were oriented improperly the caps would blow up.
Have you checked either of the two DC Link capacitors, especially C1, for leakage?
What is the DC resistance of each of the two chokes?
How much V is dropped across each of those two 15K resistors? (Thus you can calculate the total current draw of your circuit downstream from the filter.)
I am rather surprised there is not at least a small voltage drop across each of L1 and L2.
Are you running the supply with a test load? Without a load, there is no current through the circuit and therefore is not a true test of the circuit. I usually test a supply with a high wattage resistor based on the current that I intend to draw from the supply.
Your numbers appear strange since the intersection of L1, L2, and C1 is one point, so you should not get 380v and 152v at the same spot.
The DC resistance of the chokes is 140 ohms.
VDC is the same before and after the 15k resistor.
Do me a return favor, please do tell me what you hear. Thanks.
Jeff Medwin
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