Console power supply question

[jakeao]

I'm trying to figure out the wiring to my console. There are 3 voltages, 48v -15v and 15v. My quesiton is why are there 7 wires going to the circuit board? The best I can come up with is that there is one common ground, and then 2 wires for each of the three voltages. I've included some pictures so you can see what I'm talking about. Does this make any sense? Thanks fo the help.

[sonicmook56]

From looking at the regulator pins, and the group of diodes that appear to be forming a bridge, i would say the wires you have marked as the bi-polar supply are the output of the mains transformer.

Probably AC, AC, center tap and technical ground.

The output of the regulators is going to the ribbon cable header.

Kinda looks like the same thing is going on at the other side of the PCB where you have it marked at 48V

~B

[jakeao]

So to power this would I just need to get 2 transformers that step down to the correct voltage and hook them up?

[sonicmook56]

What make/model is your console?

You don't have the power transformer(s)?

Yo might need to by two, one for the bi-polar and one for phantom. I bet it will be difficult to find the correct secondary windings.

That being said, It might be easier/ more convenient to get a pair of off the shelf open frame linear's.

[sonicmook56]

This is a topic that belongs in DIY gear if a moderator wants to move it.

[jakeao]

This is a topic that belongs in DIY gear if a moderator wants to move it.

Sorry about that

Anyway. The console is a StudioMixer II. It was made by Amerimex Co. Inc. Based out of Atwood California. If you can find anything on them good luck, I couldn't The part that seems wierd to me is that I need AC coming into the above circuit. Is that correct? If so why do I have seven wires coming in instead of three? Thanks again.

[The Scum]

You need AC that's coming off the secondaries of power transformers - either a single transformer with multiple secondaries, or a pair of separate units. To get 48, you need power and ground, and to get +/- 15, you need +pwr, gnd and -pwr, making 5 lines. Add a couple more for center taps or serias/parallel connections.

Are you saying there's no power transformer?

If there isn't I'd recommend replacing the whole thing with a couple off-the=shelf industrial supplies. I really don't like the scorch on the right side of the board.

[sonicmook56]

This one should be about right for your bi-polar supply.

http://www.antekinc.com/AN-01xx.pdf

Model AN-0112

and for your phantom supply:

AN-0118

I have used several of there transformers, there good and inexpensive.

~B

[Nate Dort]

This one should be about right for your bi-polar supply.

http://www.antekinc.com/AN-01xx.pdf

Model AN-0112

and for your phantom supply:

AN-0118

I have used several of there transformers, there good and inexpensive.

~B

I don't think a 10VA torroid is going to have enough juice to power this.

Why did you recommend those specific models? How do you know what transformer secondary voltages are needed here? Did I miss a schematic somewhere?

[jakeao]

I don't think a 10VA torroid is going to have enough juice to power this.

I wonder about this myself. The regulators that are in there put out 1.5 amps. But I also am not sure.

Are you saying there's no power transformer?

Yeah what's in the picture is all I have. Are you saying to get a power supply that gives me the DC voltages I need and just by passing what's here now?

[sonicmook56]

This one should be about right for your bi-polar supply.

http://www.antekinc.com/AN-01xx.pdf

Model AN-0112

and for your phantom supply:

AN-0118

I have used several of there transformers, there good and inexpensive.

~B

I don't think a 10VA torroid is going to have enough juice to power this.

Why did you recommend those specific models? How do you know what transformer secondary voltages are needed here? Did I miss a schematic somewhere?

Your right. I'm not paying attention. let's look at it closer. Schematic not needed for this basic circuit, but If you need something, you can reference a Fairchild data sheet to get an idea.

The, 78xx,79xx series regulators are rated for 1A output. Being such a robust device, one can add a large heat-sink and push the regulator up to about 1.5A before the internal thermal protection circuit shuts it down. Since pushing chips like that cause failure, and failure means warranty returns, and warranty returns means less profit, I would also ASSume the designer would use a more capable device if the load demanded it. (however, this might be why they are un-google-able)

so, we need to figure out what the secondary windings need to be and how much current they need to deliver. Because the v-regs are 15V, and we know the device will regulate input voltages up to about 35V we can start looking at transformer secondary windings.

Multiply the secondary voltage by 1.5 to get the rectified un-regulated DC voltage.

12 * 1.5 = 18

A bad choice (sorry for suggesting it) because real world situations such as the summer when the AC coming out of you wall is a few volts lower. Also, when the transformer is under load, it won't give you what it says it will on the box.

it might be smarter to use a 15V winding.

15 * 1.5 = 22.5

OK, it's a better choice.

Now how much "umph" can the transformer promise? Volt amps is basically watts without thinking about the voltage and current being out of phase with each other. I don't like math nor do I work with AC, so I'll use Ohm's law to figure out Watts and round up to a xfmr that is available while referencing data sheets.

15V into one amp (the suggested maximm of the 78xx,79xx) is 15W Because it's a transformer, and transformers are not perfect, you loose efficiency.


http://www.antekinc.com/AN-0215.pdf

This a 20VA unit. The data sheet says it can deliver 1.6A at 14V, but wired in parallel. Since were over engineering here let's go with this one.

http://www.antekinc.com/AN-0515.pdf

Full load, 3 amps output.

I bet the console with a few chips (probably TL074's or something) per channel won't make either of these units sweat much.



~B

[The Scum]

Are you saying there's no power transformer?

Yeah what's in the picture is all I have. Are you saying to get a power supply that gives me the DC voltages I need and just by passing what's here now?

I'm saying you've only got half a power supply there. There should be a pretty hefty transformer along with it.

If there isn't, you're faced with a couple of choices: if you're confident in your DIY skills, you can track down some new transformers to replace the missing one...but you'll basically be reviving a supply that looks pretty marginal to begin with. If everything that Sonicmook just wrote is gibberish to you, I'd advise you don't try that. It involves connecting to wall AC, and there is a potential for shock & fire if you get it wrong.

The other option would be to replace it with a new DC power supply or two...Power One linear or Acopian Gold Box supplies. They're good supplies, but still require a fair amount of wall AC wiring to get working.

If you don't understand how to do the AC wiring, please find someone experienced to help you in person, to help you avoid sparks & smoke.

[jakeao]

Thanks for the great info. It's been too long since I've done this stuff. I can finally start putting the pieces together. To make sure I understand this, I would need one of the AN0515s for the 15V, and then a transformer that gives me 48V. The one I found on the same site (AN-10248) seems a bit excessive.

I also foudn this one that seems like it would work.

http://www.newark.com/hammond/166k35/bo ... tid=223366

[jakeao]

One other thing just popped into my head. I have seven wires connected to the board. 6 would be for the -15, +15, and 48 volts, but what is the last one for? If it's a ground how do I wire that up? can I just connect it back to the ground on the cord that will plug into the wall from my power supply?

[jakeao]

I got the console working. sounds pretty good too. I haven't given it a full out trial run, but should be on Friday. Thanks for all the great info to get me pointed in the right direction. The TapeOp community rocks!!