Placid BP troubleshooting help please
I'm having an issue with my Placid BP power supply and was hoping for some assistance to figure it out. If this is the incorrect place to post this, I apologize.
I'm using it to provide +/- 15v to the analog section of my DIY DAC. It's been in use for a month or so now with no issues. I noticed the other night the LEDs on the negative side of the board weren't lit any more. Touched the heatsinks on that side, they were cool to the touch. Measured approx 20v (I'm using an 18v transformer) at AC2, there is the same reading (2.0v) across D1/D2 as D3/D4. I'm unable to adjust VR3 to get V- into where I need it, -15.0v. The closest I can get it is about -16.8v. I've gone through and done the adjustments to the negative side of the PS as outlined in the First Steps portion of the manual with no change.
Any guidance is appreciated, I don't have a great deal of experience with electronics so please don't assume I know anything 😕
Ben
I'm having an issue with my Placid BP power supply and was hoping for some assistance to figure it out. If this is the incorrect place to post this, I apologize.
I'm using it to provide +/- 15v to the analog section of my DIY DAC. It's been in use for a month or so now with no issues. I noticed the other night the LEDs on the negative side of the board weren't lit any more. Touched the heatsinks on that side, they were cool to the touch. Measured approx 20v (I'm using an 18v transformer) at AC2, there is the same reading (2.0v) across D1/D2 as D3/D4. I'm unable to adjust VR3 to get V- into where I need it, -15.0v. The closest I can get it is about -16.8v. I've gone through and done the adjustments to the negative side of the PS as outlined in the First Steps portion of the manual with no change.
Any guidance is appreciated, I don't have a great deal of experience with electronics so please don't assume I know anything 😕
Ben
Correct. I don't see any burning or obvious signs of damage inside the LED, either.
Can you measure the voltage across R15 please. We can use this to figure the current going through the LEDs.
Ok that works out to about 11ma if you are using a 21R resistor there(I am pretty sure that's what we supply).
11ma is just fine. So we know the JFET and R are doing their job being a current source.
Then next thing to do is with the power off check for shorts across all caps.
Also after you do that tell me the voltage across R18
11ma is just fine. So we know the JFET and R are doing their job being a current source.
Then next thing to do is with the power off check for shorts across all caps.
Also after you do that tell me the voltage across R18
R18 is .26v.
Oddly, after turning the board over a couple times to check the voltages, the LEDs were lit and I was able to adjust V- to where I need it. Since I started this post, the LEDs are now off, and the reading at V- has gone from -15.0v to -27.4v.
How would I go about checking the caps for shorts?
Oddly, after turning the board over a couple times to check the voltages, the LEDs were lit and I was able to adjust V- to where I need it. Since I started this post, the LEDs are now off, and the reading at V- has gone from -15.0v to -27.4v.
How would I go about checking the caps for shorts?
I think you will find the problem is a cold solder joint(s) or a lose wire. Caps don't short and unshort.
Just to be clear. I did not expect the caps themselves to be shorted (though that is possible) but most any short elsewhere in the circuit would show up when you measure across the caps because it would be in parallel with one of them,. 🙂
I Agree with Brian, it is likely a cold joint.
I Agree with Brian, it is likely a cold joint.
Humm?
Would Placid help performance of my Buffalo24 boards?
Realizing Buff24 has series regs on the board for dig and ana sections.
Just checking out the Placid, would there be any benefit for Buff24 to
using shunt reg? If so would best benfit be realized by bypassing onboard regs.
Would analog only side benefit more than digital side?
Would Placid help performance of my Buffalo24 boards?
Realizing Buff24 has series regs on the board for dig and ana sections.
Just checking out the Placid, would there be any benefit for Buff24 to
using shunt reg? If so would best benfit be realized by bypassing onboard regs.
Would analog only side benefit more than digital side?
I have the original LCD and LCBPS supplies I'm using on a different dac. They made a big sonic difference. I've been waiting for the shunts to come out.
I read on the previous pages these should be lower noise. Do you suspect it will be a day/night difference? Or just quieter and better low level detail?
I read on the previous pages these should be lower noise. Do you suspect it will be a day/night difference? Or just quieter and better low level detail?
Russ,
See above about using with the Buffalo24.
Digital side or analog side - benefit most?
Bypass onboard regs?
See above about using with the Buffalo24.
Digital side or analog side - benefit most?
Bypass onboard regs?
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The most benefit would be on the analog side.
You could use it in place of the on-board AVCC reg on the BUF24, but I am not sure if that would be better or not. I simply have not tried it.
Cheers!
Russ
You could use it in place of the on-board AVCC reg on the BUF24, but I am not sure if that would be better or not. I simply have not tried it.
Cheers!
Russ
Placid BP PS revision 1.0 for PCB revision 2.1.2
I need to know when you said at the manual of Placid BP PS revision 1.0 for PCB revision 2.1.2:
"Now adjust the CCS pots (VR1/VR2) until the measured voltage across R1 & R2 are ~0,25V"
So the voltage measured across R1 & R2 coul be 15,25V to 14,75V, not 0,25V, right?
I need to know when you said at the manual of Placid BP PS revision 1.0 for PCB revision 2.1.2:
"Now adjust the CCS pots (VR1/VR2) until the measured voltage across R1 & R2 are ~0,25V"
So the voltage measured across R1 & R2 coul be 15,25V to 14,75V, not 0,25V, right?
You should measure the voltage across each separately.
Directly across each resistor (from lead to lead).
Cheers!
Russ
Directly across each resistor (from lead to lead).
Cheers!
Russ
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