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Problem with Placid Single PS max 3.6V output,problem found, new problem
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Hi, i've just builded the placid single power supply without the rectifier brigde because i am using a 12V battery to supply my dac and adjusted the trimpot how it is described in the manual. after i connect the battery i get a maximum Vout of 3.6V. if trim down vr2 to 2k(for 6V i need) i have a output of 2.6V? whats wrong in my setup? EDIT: i found out that i have c5 in the wrong direction. :( now after i corrected this i cant only regulate between 3.4V and 2.6V. some thing i have disturbed. maybe someone who has more knowing can say me what i can measure and maybe what i have blown because the wrong C5 direction. thanks a lot carlosz Edited by user Thursday, April 14, 2011 9:53:10 AM(UTC)
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Hi
I had similar problems using a replacement JFET which had similar specs as the PN4393. (not enough voltage OR not enough current)
The problem is there is a lot of dispersion in those parts IDss (even parts coming from a same batch can vary by a factor of 3 or 4), could be your JFET's IDSS is not high enough (I think a value of 10 is needed, but the PN4393 can go as low as 5... I think a PN4392 would be better suited) . Did you buy the JFET yourself or got it with the TP Kit ?
How low did you go for VR2 value ? The starting point given in the manual is actually quite far from the sweet spot required to get 6V.
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The Placid is designed to cope with the IDSS differences. Also Brian rejects JFETs with IDSS too low. VR2 value is just fine. Something else is clearly wrong based on your description. :) Are you checking with no load? What do you have the CCS current set to? Any chance you can post pictures? Edited by user Friday, April 15, 2011 10:54:15 AM(UTC)
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Yes C5 backward is bad, but should not have caused what you are seeing.
What voltage do you get when you measure across C5 while powered?
What voltage do you get when you measure across C1 while powered?
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Russ White wrote: Also Brian rejects JFETs with IDSS too low.
Which is why I'm asking if he purchased the kit or bought the parts by himself.... I tell you at IDSS=5 the thing does not allow enough adjustment for every need (although voltage adjustment SHOULD be possible up to 6)
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Russ White wrote:Yes C5 backward is bad, but should not have caused what you are seeing.
What voltage do you get when you measure across C5 while powered?
What voltage do you get when you measure across C1 while powered? Hi Russ, thanks for helping. i measured on c1 12.5V and on c5 4.14V regards carlosz
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Are you testing with or without a load?
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Russ White wrote:Are you testing with or without a load? without load only a 12V battery as supply connected and both leds are lightning. i can attach a picture if needed. thanks carlosz
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The is starting to sound like a transistor is swapped. Double check the the correct part is in the correct place.
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Russ White wrote:The is starting to sound like a transistor is swapped. Double check the the correct part is in the correct place. i checked it twice before i request any support ;) and now i will recheck it again but i think all transistors are in correct place. i've build up a second placid single without any problems. only the first will not function correctly. thanks carlosz
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That raises my suspicions all the more. :)
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Russ White wrote:That raises my suspicions all the more. :) Hi Russ, i checked it again,again,again... ;) qp1=FJPF1943RTU,qn=FJPF5200OTU,qp2=bc560b,q2=2n4393. i gave it up. i dont know whats wrong with this psu. i can send you a pic of the psu if you want. thanks again and happy easter carlosz
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Here in the threat you can post a picture. Then we all can try to help you. Edited by user Friday, April 22, 2011 12:39:04 AM(UTC)
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avr300 wrote:Here in the threat you can post a picture. Then we all can try to help you. Hi, how i can attach a pic to the post? Ohhps i have found it;)) thanks Edited by user Friday, April 22, 2011 5:51:46 AM(UTC)
| Reason: Not specified carlosz attached the following image(s):  placid_nok_c1.JPG (117kb) downloaded 111 time(s).You cannot view/download attachments. Try to login or register.
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One observation, even when using an external DC source you would be wise to leave the rectifier in place. That way you cannot possibly connect reverse polarity. If you ever did connect reverse polarity they way you have it now you would almost certainly destroy the power supply.
If you can use a flash so I can tell part orientation and such. Also a picture of the bottom of the board would be helpful.
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Russ White wrote:One observation, even when using an external DC source you would be wise to leave the rectifier in place. That way you cannot possibly connect reverse polarity. If you ever did connect reverse polarity they way you have it now you would almost certainly destroy the power supply. If you can use a flash so I can tell part orientation and such. Also a picture of the bottom of the board would be helpful. Hi again, i hope this one is better to analyze ;) thanks a lot karsten Edited by user Monday, April 25, 2011 7:36:16 AM(UTC)
| Reason: Not specified carlosz attached the following image(s): placid_nok_014.jpg (179kb) downloaded 75 time(s).You cannot view/download attachments. Try to login or register.
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Problem with Placid Single PS max 3.6V output,problem found, new problem
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