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Placid 2.01 Max out is only 250ma need help troubleshooting
Rank: Member
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Joined: 11/10/2010(UTC)
Posts: 30
Location: Campbell, CA
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Hey Guys,
So I've attempted to setup a number of Placid power supplies now and have succeeded in making one work but the other I have is experiencing issues and I'd appreciate some help in troubleshooting. So first off the one I'm working on now I purchased my own parts and not a kit...I used all the same values for the parts as listed in the BOM. I have verified all resistances throughout the board is as per the BOM.
However when I power the unit with 9V AC I am only able to achieve .25V when measuring R8. I have replaced R5 with a 4.7Ohm resistor as I have the Tridents installed on my Buff II so I'm hopping to achieve .5V to .6V across R8. However this does not occur and with VR1 set to max resistance of around 200ohm I can only achieve .25V as stated across R8.
What should I check first...could it be I fried or otherwise damaged the IC on the board while soldering it on? Also I'm a little confused as to how increasing the resistance of VR1 would produce the highest voltage level vs. the lowest voltage level...doesn't more resistance in the circuit basically mean less voltage / current in this case?
I certainly a noob to electronics so if someone can point me in the right direction of discovering what is messed up here I'd great appreciate it.
Best Regards,
Theo
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Rank: Administration
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Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
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First, this is pushing the placid right to the edge. but I think we can make it work.
Here are a couple of things you could try.
First double check that your input is not sagging under the load. Measure the voltage across the smoothing caps.
If it is not sagging first try simply using a jumper for R5.
If that did not do the trick, then you may need to try a higher value for R1.
Cheers!
Russ
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Rank: Member
Groups: Member
Joined: 11/10/2010(UTC)
Posts: 30
Location: Campbell, CA
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Thanks Russ,
I will give it a shot. Strange thing is that the one placid I have configured in a similar manner reached .5v across R8 no issues. I am using slightly different parts on this one but the resistors are the same values ... I guess the caps could have something to do with it. I will check and get back to you. Also what is the ideal R8 value to shoot for if you are connecting up a Buffalo-II with Trident Regs installed? Should I measure with the load connected cause as it is I am measuring without the Buff-II connected.
Best Regards,
Theo
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Well you just making the shunt work really hard with no load. Because all the of the power that would normally be used by the load is now being shunted.
The reason for the difference between two placids is really just variation between JFETs. They have a pretty wide range of Idss.
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Rank: Member
Groups: Member
Joined: 11/10/2010(UTC)
Posts: 30
Location: Campbell, CA
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Here are the voltages I'm getting:
A1-AC 9.07
A1-DC 10.14
VR1 0.881 196.5ohm
VR2 4.017 2.8k ohm
R1 0.881
R2 4.017
R3 0.235
R4 0.86
R5 0.034
R6 0
R7 1.422
R8 0.251
C1 10.1
C2 10.07
C3 0.002
C4 0.758
C5 4.014
C6 0.879
I jumper-ed R5 and now I'm getting .275V but no more than that. What could be wrong...can different caps and resistors than the ones provided in the kit really cause this much voltage drop...also what would cause a sag?
Best Regards,
Theo
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Well you could just be at the very maximum current for that particular JFET. You could try swapping it for one with higher Idss or simply using a higher value for VR1.
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Placid 2.01 Max out is only 250ma need help troubleshooting
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