ccfreimuth wrote:Hello everybody, first post here.
I've built the power plant and powered it up without issue, however, I'm getting around 17v and 35v on the 24v and 48v rails, respectively. Adjusting the trim pots doesn't afford the amount of adjusting required, so what did I do wrong here? Mains voltage coming in is accurate. Also, I don't yet have it mounted in the die-cast aluminum enclosure I'm using for it, so would this present an issue when simply testing for these output voltages?
Thanks in advance for your assistance in figuring this out.
Best,
Connor
HI Connor
Attach some photos of the build so I can check it over and especially of the regs under the PCB with the silicon tubes removed.
Do you have the metal tabs on the regs facing away from the pcb?
Concerning the spot marked "case," I'm assuming this is the one and only connection to chassis from the power supply board.
Can the AC mains earth ground still connect to chassis right by the IEC input connector like usual, or do I have to route it to this "case" spot on the power plant board? Same question for the shield of the power supply cable that connects to the preamps' chassis. Can it be locally connected to chassis where it comes in the box, or do I have to ground it right at that mounting screw where the power plant ground is connected to chassis? I ask because I thought it was common practice to have the earth ground, power supply 0V ground and chassis all connected at one point only, usually close to the AC input. ???
Second question. I read on some obscure thread about Joe recommending aluminum for the chassis. Bummer, because I have a handsome electrical junction box that is steel. I should also mention it is painted. Will this be okay? It's quite small as well, and I'm powering 4 channels of 1290's. Ruh roh?
Jonk wrote:Concerning the spot marked "case," I'm assuming this is the one and only connection to chassis from the power supply board.
Can the AC mains earth ground still connect to chassis right by the IEC input connector like usual, or do I have to route it to this "case" spot on the power plant board? Same question for the shield of the power supply cable that connects to the preamps' chassis. Can it be locally connected to chassis where it comes in the box, or do I have to ground it right at that mounting screw where the power plant ground is connected to chassis? I ask because I thought it was common practice to have the earth ground, power supply 0V ground and chassis all connected at one point only, usually close to the AC input. ???
Mains ground from the IEC mains input always goes direct to chassis with bolt and lock washers (do not put mains ground wire to one of the bolts holding in the IEC socket as this involves plastic which is not allowed in the chassis bolt assembly) and then from chassis bolt to the case bolt on powerplant. If you use metal standoffs or full bolt between chassis and case then no wire is needed to powerplant.
Second question. I read on some obscure thread about Joe recommending aluminum for the chassis. Bummer, because I have a handsome electrical junction box that is steel. I should also mention it is painted. Will this be okay? It's quite small as well, and I'm powering 4 channels of 1290's. Ruh roh?
It depends on the thickness of the metal. 1mm to 1.6mm steel doesn't flow the heat very well especially if painted. So best to cut a thick aluminium plate for under the power plant to spread the heat inside into the metal chassis better but then vetn holes would also be useful to let the heat out. A whole 3mm thick diecast box spreads the heat well with lots of surface area to dissipate the heat. Remember the best heatsinking or spreading the better the power supply will work for a longer time.
papiblu wrote:Oh, I thought I sent it attached.
Let me try again
The bottom of the pcb needs a good clean with isocol or iso prop and toothbrush to see properly but I can see that one centre leg on the trimpot has never been soldered so will not work. Since the 3 x 120R burnt the 48v reg is likely to be dead short or open.
Was anything connected to the output of the power supply when is blew the 3 x120R?
Hi thanks for your reply.
I cleaned the pcb with isopropilic, but is dificult to take a picture showing the traces, cause it shines with the light
I hope you can see something.
So I have to change one of the regs, or better both?
The trim for the 24v now doesn't works, I dont know if I turned too many times the litle screw... so only marks 35v
When the 3x120 burned it was connected to the 24v in of the PreAmp (a german card)
Thank you Joe
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papiblu wrote:Hi thanks for your reply.
I cleaned the pcb with isopropilic, but is dificult to take a picture showing the traces, cause it shines with the light
I hope you can see something.
So I have to change one of the regs, or better both?
one or both
The trim for the 24v now doesn't works, I dont know if I turned too many times the litle screw... so only marks 35v
Once you turn the resistor above the 35v which is the high unreg volts the trimpot will do nothing until it is turned down several turns. Encase you have blown the reg on the 24v rail which will also make it stay at 35v it is best to reset the trimpot to 2.5k while the power supply is off. And then power up and see if you have less than 35v on the 24v reg. If so adjust ot the 24v. IF not
When the 3x120R burned it was connected to the 24v in of the PreAmp (a german card)
The 3 x 120R are only in the 48v rail so this means you connected the 48v rail to the 24v of the preamp which would have overloaded it totally burning the 3 x 120R. Also do not try to set the 48v rail to 24v as it cannot drive the 24v the preamp needs.
papiblu wrote:Hi Joe,
I CHanged the Regs and everything works fine now.
Thank you for your help.
I have a question too.
In the power plant page, its written that can feed 4 modules.
Even those telefunken or neumann cards with 2 channels per module??
Thank you!
Cool great to hear you got it working ok. As long as the total 24vdc current is less than 800mA and the metal case used for heatsinking the regs has enough thickness to dissipate the heat. 4 x Neve modules draw about 500mA. The telefunken and Neumann cards usually do not draw that much current when compared to the neve modules so you will be fine.
