fucanay
Well-known member
EDIT #2: After a lot of fussing around with this thing, I gave up on this PSU and went for an all JLM solution. Which includes the JLM TREX PSU boards along with the 48v 380mA SMPS. Using a star grounding scheme, this removed all of the oscillation and noise problem I was having with no other modifications needed. This is by far the easiest and cheapest solution. The Green Pre PSU just presented too many problems for this preamp.
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This is the Solution to the thread below. I think this is quite useful to many less experienced DIYers, so I'm amending the first post to show what has been changed to make the Green Pre PSU work for the FETboy. Or for that matter, anyone needing +24 and +48 from the same supply.
First, this is what the board looks like: Green Pre PSU configured for +24 and +48
This is an edited schematic that shows the circuit as I'm using it: FETBOY PSU Schem
1. The parts surrounded in yellow are omitted. These were for the -15V side of the PSU that the Green Pre needed.
2. The Green line within the yellow box is a jumper. This is needed so the ground plane on the PSU is connected with the PSU configured in series.
3. To get the +24 volts in this circuit, you'll need to adjust some resistor values around the LM317 regulator. In the original circuit R1 was marked 2k2 and R2 was marked 220R. R1 and R2 have been changed to 2k to coincide with the values suggested by the LM317 calculator.
Many, many thanks to everyone who helped me in this thread. You guys beat it into me and it helped me a lot.
EDIT: After switching to a 12-0-12 transformer, everything is good to go. Input voltage = 28.8VAC, rectified voltage = 38VDC, regulated voltages = +23.9VDC and +47.7VDC.
Matt
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The original post starts here
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matta gave me this drawing detailing how to set up Peter C's Green Pre PSU to work with the FETboy Preamps.
This details what parts to leave out for the negative side of the PSU (surrounded in yellow) and where to jumper it (in green, on the bottom right). Matt used a 48VCT transformer to do this.
The original schematic is here.
I've edited it to reflect Matt's changes here., except that I have not changed the transformer to 24-0-24. I have left the 15-0-15 in place. Because using the mnats PSU boards, you can use the same 15-0-15 transformer using a trimmer to get what ever voltages you need within the limitations of the regulators. But getting to +24V should be no problem.
Now, I'm not very good with these things and don't really understand how to adapt all of this stuff, so that is the reason for this thread. There is no place for a trimmer on the Green Pre PSU, so I would need to change some resistor in the PSU to get more DC volts to the LM317 regulator, I guess. But I have no idea which needs to be changed or to what it should be changed to.
Is anyone able to point me in the right direction?
Matt
______________________________________________________________________________________
This is the Solution to the thread below. I think this is quite useful to many less experienced DIYers, so I'm amending the first post to show what has been changed to make the Green Pre PSU work for the FETboy. Or for that matter, anyone needing +24 and +48 from the same supply.
First, this is what the board looks like: Green Pre PSU configured for +24 and +48
This is an edited schematic that shows the circuit as I'm using it: FETBOY PSU Schem
1. The parts surrounded in yellow are omitted. These were for the -15V side of the PSU that the Green Pre needed.
2. The Green line within the yellow box is a jumper. This is needed so the ground plane on the PSU is connected with the PSU configured in series.
3. To get the +24 volts in this circuit, you'll need to adjust some resistor values around the LM317 regulator. In the original circuit R1 was marked 2k2 and R2 was marked 220R. R1 and R2 have been changed to 2k to coincide with the values suggested by the LM317 calculator.
Many, many thanks to everyone who helped me in this thread. You guys beat it into me and it helped me a lot.
EDIT: After switching to a 12-0-12 transformer, everything is good to go. Input voltage = 28.8VAC, rectified voltage = 38VDC, regulated voltages = +23.9VDC and +47.7VDC.
Matt
--------------------------------------------------
The original post starts here
--------------------------------------------------
matta gave me this drawing detailing how to set up Peter C's Green Pre PSU to work with the FETboy Preamps.
This details what parts to leave out for the negative side of the PSU (surrounded in yellow) and where to jumper it (in green, on the bottom right). Matt used a 48VCT transformer to do this.
The original schematic is here.
I've edited it to reflect Matt's changes here., except that I have not changed the transformer to 24-0-24. I have left the 15-0-15 in place. Because using the mnats PSU boards, you can use the same 15-0-15 transformer using a trimmer to get what ever voltages you need within the limitations of the regulators. But getting to +24V should be no problem.
Now, I'm not very good with these things and don't really understand how to adapt all of this stuff, so that is the reason for this thread. There is no place for a trimmer on the Green Pre PSU, so I would need to change some resistor in the PSU to get more DC volts to the LM317 regulator, I guess. But I have no idea which needs to be changed or to what it should be changed to.
Is anyone able to point me in the right direction?
Matt