AC/DC & POWERSTATION KIT BUILD THREAD

[Joe Malone]

hey there,

What am I supposed to do if I for example didn't want the +48V rail from the AC/DC kit?

What parts should I leave out?

Same goes for the powerstation, in case I wouldn't want +V1 and -V1?

Does is suffice if I just leave out the linear regulator 317 / 337?

---

This question is a bit more specific. I'm using two transformers and two psus for a single preamp box (reason being that includes two ssl9k (+ - 16) and two neves ( + - 24). Whereas the transformers and psus are in a separate box. Anyhow, the question is whether I can power all four pres from the same +48V rail and leave the 48 V rail of the other psu out?

See voltage section breakdown for powerstation and AC/DC kit below. I will try to do some new virtual PCB jpg's when I can to make some easier to read versions.

As for the shared 48v for 4 mic pres that will work fine as long as both power supplies have there 0v connected together.

[Joe Malone]

Hey joe..Thanks for your reply..
I have my built power station kit here with the 6 amp bridge .. so if i wanted to get 3 amp rails with the cap & bridge kit can i leave my 6amp rec in place or do i have to remove it and replace them with the smaller diodes?

You can leave any diode type or bridge in place as they will not turn on when the new bridge and cap kit is used. Since you have the 6amp bridge you could just add 2 large 10000uF caps across each positive and negative cap bank for extra smoothing. See below powerstation cap bank breakup for which caps to link across. The bridge and cap kit just makes a neat way of adding the extra capacity.

also do i just bridge say +v1 and +v2 at the terminal block with the 1 watt resistor after setting voltages..??

Yes a 0.22ohm 1w resistor in series with each output like shown below will give 3A +/- power rails. (power rails must have there voltages set before the resistors are connected)


Or a 3Amp diode in series with each output like shown below will give 3A +/- power rails. (voltages can be set with diodes already connected but you will need to set the voltage 0.7v higher on each rail to makeup for the diode drop.)

[atticmike]

hey there,

What am I supposed to do if I for example didn't want the +48V rail from the AC/DC kit?

What parts should I leave out?

Same goes for the powerstation, in case I wouldn't want +V1 and -V1?

Does is suffice if I just leave out the linear regulator 317 / 337?

---

This question is a bit more specific. I'm using two transformers and two psus for a single preamp box (reason being that includes two ssl9k (+ - 16) and two neves ( + - 24). Whereas the transformers and psus are in a separate box. Anyhow, the question is whether I can power all four pres from the same +48V rail and leave the 48 V rail of the other psu out?

See voltage section breakdown for powerstation and AC/DC kit below. I will try to do some new virtual PCB jpg's when I can to make some easier to read versions.

As for the shared 48v for 4 mic pres that will work fine as long as both power supplies have there 0v connected together.

concerning the powerstation, if I didn't want the -V2 and +V2 rail, I'd simply have to remove the two caps, two diodes, single regulator and 120R resistor each?

[Joe Malone]

concerning the powerstation, if I didn't want the -V2 and +V2 rail, I'd simply have to remove the two caps, two diodes, single regulator and 120R resistor each?

If the powerstation is already built I would just leave the extra parts on as they are not under load so unlikely to fail.
But you could just remove the regulators you are not using to get them out of the way of shorting to the chassis etc.

[pope]

Hi Joe,

I want to use the AC/DC with a 63VA, 2 X 30V Transformer to supply my circuit with +/-28V and +5 volts.
Are there any mods you would suggest in order to improve the PSU for the specific requirements (i.e different values for the smoothing caps, etc..) ?

Thanks
Pope

[Joe Malone]

Hi Joe,

I want to use the AC/DC with a 63VA, 2 X 30V Transformer to supply my circuit with +/-28V and +5 volts.
Are there any mods you would suggest in order to improve the PSU for the specific requirements (i.e different values for the smoothing caps, etc..) ?

Thanks
Pope

What current will the +/-28v rails draw? And especially what current will the 5v rail draw? So I can do the calculations. If you are not sure of the current let me know what the power supply will be connected too.

If the 5v rail is for relays it is dropping around 35v it will be running hot. It is always best to make the relays as high as volts a possible so less current is used and less voltage is dropped across the regulator.

[pope]

Hi Joe,


For the +/-28V rails:
My DMM shows around 150mA per channel on the +28V rail (and around 20mA on the -28V rail) so that’ll be around 300mA for two channels.
However, I’d like to add one LED on each rail for power indication. So, maybe 400mA for both channels?

For the +3rd rail:
The +5V rail is used for a couple of LEDs (for bypass indication) with the following specs:

Forward Peak Current: 30mA
Continuous Forward Current: 20mA
Forward Voltage: 3.6V
Reverse Peak Voltage: 5V

The way I’ve connected the LED (with a series resistor) I get about 1.5mA per LED and the regulator is pretty hot indeed.
Maybe I can increase the value of the series resistor and set the regulator to around 15-20V?
But then, I guess the resistor will get hot…

Hope all that make some sense and thanks for all your help! ☺
Pope

[Joe Malone]

Hi Joe,


For the +/-28V rails:
My DMM shows around 150mA per channel on the +28V rail (and around 20mA on the -28V rail) so that’ll be around 300mA for two channels.
However, I’d like to add one LED on each rail for power indication. So, maybe 400mA for both channels?

For the +3rd rail:
The +5V rail is used for a couple of LEDs (for bypass indication) with the following specs:

Forward Peak Current: 30mA
Continuous Forward Current: 20mA
Forward Voltage: 3.6V
Reverse Peak Voltage: 5V

The way I’ve connected the LED (with a series resistor) I get about 1.5mA per LED and the regulator is pretty hot indeed.
Maybe I can increase the value of the series resistor and set the regulator to around 15-20V?
But then, I guess the resistor will get hot…

Hope all that make some sense and thanks for all your help! ☺
Pope

OK that will all work fine with no component changes. Just do the below steps.
1. Disable the 48v rail voltage doubler as per the instructions on the bottom overlay of the AC/DC pcb
(short out C1 and C2 and don't fit any doubler/tripler jumper)
2. Set 48v rail to 5v but yes it is way better to use a higher rail like 15 to 20v etc and larger resistor value to the LED to keep heat in the reg down.
(using the higher rail should allow all regs to be heatsinked just by the side of the standard rack case but always more heatsinking the better.)

[pope]

OK that will all work fine with no component changes. Just do the below steps.
1. Disable the 48v rail voltage doubler as per the instructions on the bottom overlay of the AC/DC pcb
(short out C1 and C2 and don't fit any doubler/tripler jumper)

I have Version 2 PCB. Do the same mods apply?

Also, just to double check...
My new Transformer (2x30 60VAC) labels the seconadries as:

BLACK - RED 30V
ORANGE - GREY 30V

For +/-28V I connected BLACK/ORANGE at 0V and RED and Grey at the 2 AC pins. That obviously is wrong and although I was getting the correct voltages on the +/- regulators, the +48V rail burned the 120-Ohm resistor. The reason I wired this way is because up until today (for the last couple of years) I was using a 2x25V 50VAC transformer wired the same way and it was working fine (so I hadn't realise it was wired wrong!). It should be RED/ORANGE at 0V and Red/Grey in the AC pins, right?

Apart from the burnt resistor shall I also replace the regulator? I haven't connected the transformer after the 120Ohm replacement but when I measure the resistance in the 5K trimmer it's constantly rising until it reaches the maximum my DMM can read. The other two trimmers read around 2.5Kohms each.

[Joe Malone]

OK that will all work fine with no component changes. Just do the below steps.
1. Disable the 48v rail voltage doubler as per the instructions on the bottom overlay of the AC/DC pcb
(short out C1 and C2 and don't fit any doubler/tripler jumper)

I have Version 2 PCB. Do the same mods apply?

yes

Also, just to double check...
My new Transformer (2x30 60VAC) labels the seconadries as:

BLACK - RED 30V
ORANGE - GREY 30V

For +/-28V I connected BLACK/ORANGE at 0V and RED and Grey at the 2 AC pins. That obviously is wrong and although I was getting the correct voltages on the +/- regulators, the +48V rail burned the 120-Ohm resistor. The reason I wired this way is because up until today (for the last couple of years) I was using a 2x25V 50VAC transformer wired the same way and it was working fine (so I hadn't realise it was wired wrong!). It should be RED/ORANGE at 0V and Red/Grey in the AC pins, right?

Yes correct RED/ORANGE at 0V and Red/Grey in the AC ins

Apart from the burnt resistor shall I also replace the regulator? I haven't connected the transformer after the 120Ohm replacement but when I measure the resistance in the 5K trimmer it's constantly rising until it reaches the maximum my DMM can read. The other two trimmers read around 2.5Kohms each.

If the trim was turned down putting more than 40v across the 48v reg in and out the trim pot and 120R and reg will be dead. As text in first post on this build thread mentions. You will only be able to get down to 5 to 12v on 48v rail if the (short out C1 and C2 and don't fit any doubler/tripler jumper) mod is done.

[pope]

Excellent! I'll try it.
thanks once again

[soliton]

I notice you mention the possibility of disabling the doubler/tripler to all another V+ rail (e.g., 24VDC). Could you explain what modifications to the circuit would be required in this case?

[Joe Malone]

I notice you mention the possibility of disabling the doubler/tripler to all another V+ rail (e.g., 24VDC). Could you explain what modifications to the circuit would be required in this case?

Not sure where you get that info from as there is only a Doubler/Tripler on the 48v regs rail in any of our power supply kits. All other rails are are just full wave rectified.

[shoebag_ape]

Hi Joe,

I'm using the AC/DC with the doubled 4007 mod to increase current capability and the 'Note 3' mod to get a lower rail instead of the 48v. I've set the 48v rail down to 12v for use with relays and LEDs, but R7 is starting to blacken and smell. Is this just a case of needing to use a higher wattage resistor or have I done something wrong somewhere?

Thanks

[Joe Malone]

Hi Joe,

I'm using the AC/DC with the doubled 4007 mod to increase current capability and the 'Note 3' mod to get a lower rail instead of the 48v. I've set the 48v rail down to 12v for use with relays and LEDs, but R7 is starting to blacken and smell. Is this just a case of needing to use a higher wattage resistor or have I done something wrong somewhere?

Thanks

When "Note 3" mod is done to disable the Doubler / Tripler for the 48v rail R7 can be replaced by a wire link.