24 & 48 V w/ JLM v2 power supply

[guavatone]

I'm a bit confused on the right way to set this up. I strapped the negative rail cap and have AC going to the 2 AC pads. I have D strapped to center pad.

I am getting my +24V. The problem is I can only get 38V max on phantom unloaded. Maybe it's bad trimmer pot. I did have it hooked up for several minutes without the neg cap strapped. oh, I am getting 30 VAC from the transformers and it's got a massive heatsink.


Anyone?

Thanks in advance

 

[squib]

when you say "and have AC going to the 2 AC pads". Do you mean that you don't have the 0V pad on the input connected to the transformer?
If you are running the PSU module from a single 30Vac winding with no centre tap, then to get correct operation you need to connect one end of the winding to 0V and the other end to either one of the AC pads, leave one unconnected.

 

[guavatone]

Thanks Squib. It's a 25-0-25 XFMR and I was hoping to runn it in parallel to get the maximum amps. So I connected both sides of the xfmr to AC. It doesn't make sense in my mind that the came 0V connection for DC would have AC as well. I am not sure how to explain this but, maybe I am relating the "0" of the 25-0-25 (in series) as OK and the "25-?" AC as not OK.


Anyway, I'll just do what you said.

 

[squib]

what's the current rating of the transformer? How much current to you plan to draw from the PSU? If you have a 25-0-25 transformer it is best to hook it up using all the 0 / AC / AC inputs to the PSU module. This gives you full wave ( instead of half wave ) rectification, therefore better smoothing and better pre-reg headroom.

 

[guavatone]

It's 600 mA. i am powering 3x 283 cards with hotrod. bet I want some headroom for the 12 relays and 12 LEDs. My calcs for the LED's and Relays shows about 450mA and I think the 283 cards are about 50 mA. So it's right at 600.


I thought the center tap was moot(not necessary or functional) when the negative side was unused. right?

JLM shows this for neve:

the problem is that it is for v1 of the 3 rail PSU.

 

[JLM Audio]

I'm a bit confused on the right way to set this up. I strapped the negative rail cap and have AC going to the 2 AC pads. I have D strapped to center pad.

I am getting my +24V. The problem is I can only get 38V max on phantom unloaded. Maybe it's bad trimmer pot. I did have it hooked up for several minutes without the neg cap strapped. oh, I am getting 30 VAC from the transformers and it's got a massive heatsink.

If you are doing the +24v & +48v no -V mod for Neve etc with a single 24vac connected to both AC in's and strapping the negative cap then you actually will need to strap T to the centre hole as you will need a Tripler to get enough volts to make 48v rail work as mentioned on the above posts jpg. If you use D the unreg volts will only be about 38vdc unreg so the there will not be enough volts to make 48v. Change the Doubler strap to Tripler should have your 48v up and working. Turn the trim pot back 10 turns if you have wound it wide open on the 48v rail. (Lifting the 2 diodes on the old Ver. 1 PCB used to turn the doubler to a Tripler)

It's 600 mA. I am powering 3x 283 cards with hotrod. bet I want some headroom for the 12 relays and 12 LEDs. My calcs for the LED's and Relays shows about 450mA and I think the 283 cards are about 50 mA. So it's right at 600.

Full BA283 cards use 110mA each. Also 600mA of AC x 0.62 = 375mA DC current. Do you have the VA of the transformer so I can work out if it is 600mA per winding or total?

 

[guavatone]

Thanks for the quick reply to my email Joe. It is a 30VA xfmr and the rating is 600mA per winding =1200 mA in parallel I believe. Thanks for that AC to DC amp formula. I always thought it was the same amps. Is there a different formula for Trippling the 48V?

I will go for the trippler for now