Fuse for pm1k rack job

[buddy holly]

Okay,

I still don't have this thing ready to hook up to mains yet. I'm a little scared. I just wanted to clear a few things up first.

So I've got one leg of the IEC (L) going thru the fuse, then off to #6 on the dpdt switch. Then I've got #5 on the switch returning to #4 on the power transformer. Basically, that leg works. It's continuous with the switch in the on position and not in the off position. Like it should be.

This sounds ok.

The other leg of the IEC (N) is wired straight to #1 on the power transformer. When I'm checking continuity, Everything checks out great. However, when checking the transformer's 1 and 4 on the meter, I've got those continuous as well, but the meter makes a much higher squeal.

this is how I have done mine, but I think Scum's plan sounds a bit more thorough--and safe.

Also, what should I be hooking the ground on the IEC to? The whole thing's laid out on my desk and not in the case yet.

Once you get your case it will go directly to chassis (scratch away the paint in that spot so you get a good connection). I usually connect the - leg on the psu out ("OUT" on your Power One) to that same spot on the chassis, so for your test you can connect your "OUT" directly to IEC ground.

Next, on the power one, between the "+out" and "out" terminals, which goes to the board (and where on the board) and which goes into the orange wire for phantom?

"+OUT" gets 2 wires, one directly to +48V, and one to your diode chain or reg circuit which then goes to +44V on the pm1k board.


--BH

[phantom power]

Hey Buddy Holly, I was wondering if I'd hear from you sometime soon. As you can see, they've got me off to a good start here.

Like Buddy said, there's just a "+out" and an "out". You can see them in the bottom corner of the power one picture that's a couple posts down on the first page. No "S".

So, both the 44V and 48V are wired to the "+out" terminal, the "out" can go to the IEC ground until the chassis comes into play, what about board ground, should I tie that into the IEC's ground for now too?

Scum, to do the switch, can I then just wire "N" to #3 and out #2, then back to the transformer (effectively I'd be using both ON positions)?

Lastly, the point where the 44V should come in on the board. It looks to me like it's the red wire going to the second terminal from the right-front of the PCB. Underneath, it's labeled B+. Is this right?

If I can get all this together, I think I'll be able to fire it up tonight and drill the case later this week. Exciting!

-AE

[buddy holly]

So, both the 44V and 48V are wired to the "+out" terminal, the "out" can go to the IEC ground until the chassis comes into play, what about board ground, should I tie that into the IEC's ground for now too?

yep!

Lastly, the point where the 44V should come in on the board. It looks to me like it's the red wire going to the second terminal from the right-front of the PCB. Underneath, it's labeled B+. Is this right?

correctamundo!

And "BO" is where the output is connected. Its been generally agreed as well that the cap right before this point (C37) should be replaced with 220uf or bigger. And any point marked "E" is part of the ground plane that goes all around the pcb. Conecting to "E" on one end of the pcb is the same as connecting to an "E" on the other end. Very useful...


--BH

[phantom power]

Super sweet!!!

Man, I can't wait to get off work. I'll probably go ahead and hook it up with the switch the way it is for now, then change it when it gets in the case. I've got to add a power lamp in there somewhere anyway.

When and if this thing checks out, I'll tie in the phantom power. When I do this, do I just put a simple spst in line to turn it on/off or does it need to be dpdt on/on? I assume the latter.

Thanks BH.

-AE

[digitaldrummer]

simple spst on/off is fine for phantom.

[phantom power]

It's ALIVE!!!

It passes signal just fine. Now I just have to get through the phantom power, power lamp, DI and metalwork. Sweet!

The lamp I have is rated at 120V. Should I wire it in just after the power switch, but before it gets back to the transformer? Is there enough resistance in the lamp to mess with what the transformer needs from the AC? As far as wiring it goes, it has 2 poles. Do I just run the "L" line through it, or does it get wired differently?

Also, the power supply shows 48.2 volts. Should I trim it to be exactly 48V, or is it fine the way it is?

Thanks digitaldrummer, the Scum and Buddy Holly. You guys have been such a huge help.

-AE

[The Scum]

Put the lamp in parallel with the transformer primary. That way, they both see the full 120V.

Alternatively, use an LED and a resistor, hanging off the 48V or 44V supplies.

As for the 48.2 - how absolutely accurate is the meter you're measuring with? The .2 could just be meter inaccuracy. It shouldn't hurt anything...but go ahead if you're feeling pedantic.

[buddy holly]

It's ALIVE!!!

way to go, AE! Fun, isn't it? Careful with this stuff, you'll never get any recording done.

Put the lamp in parallel with the transformer primary. That way, they both see the full 120V.

Alternatively, use an LED and a resistor, hanging off the 48V or 44V supplies.

Hey Scum (I feel strange calling you that), I've always used 120V-rated lamps, mostly b/c that was what i had lying around. I put them in parallel with the primaries like you said, but what do you do on the DC side with the lower voltage LED's? one leg to ground?

--BH

[phantom power]

#5 on Switch------------------#4 on Transformer
#5 on Switch-----Lamp------#4 on Transformer


Sorry for the crude drawing, is this what you meant? So the wire leaves "L" on the IEC, hits the series conected fuse, then the power switch (this all stays the same, right?).

From the switch (this is where my beautiful drawing comes in), I would leave the connection that I've already made back to the transformer, but also have another wire going from the same tab on the switch to one leg on the lamp, then connect the other leg to the same spot on the transformer. Do I have this right?

BH, those 2 jacks you sent with the case, are those switching jacks? I fiddled with them for a minute and realized that as the tip of the plug goes past each of the 3 (legs?), it disengages it from what seems to be the ground side of the jack. How would I use these for the DI?

Geez... I should just give these to you guys when I'm done; you're doing all the work.

Maybe I'll take all this stuff and compile it into one nice and neat guide. That way the next shlump to come along with pm1000 modules won't have to bother you guys.

-AE

[phantom power]

For the lamp, I tried the above when I got home and I got nothing. Then I tried doing it all as I outlined except, I took that second leg on the lamp and ran it back to the "N" side of the IEC. It works and I still see 120VAC showing up at the transformer.

So, is this fine?

-AE

[The Scum]

Hey Scum (I feel strange calling you that), I've always used 120V-rated lamps, mostly b/c that was what i had lying around. I put them in parallel with the primaries like you said, but what do you do on the DC side with the lower voltage LED's? one leg to ground?

I don't like the idea of running AC all over inside a chassis, if I can avoid it. I'll use an LED hanging off a DC rail. The cathode goes to a resistor, which goes to ground. The resistor is scaled to give me ~10mA from whatever the supply voltage is.

For the lamp, I tried the above when I got home and I got nothing. Then I tried doing it all as I outlined except, I took that second leg on the lamp and ran it back to the "N" side of the IEC. It works and I still see 120VAC showing up at the transformer.

That sounds right. Effectively, you want one leg of the lamp tied to pin 4 on the transformer, the other tied to pin 1 (or points in common with them in the circuit).

You're only using 2 pins on the power switch, right? The neutral side of the transformer is just unbroken wire back to the N on the IEC?

[phantom power]

You're only using 2 pins on the power switch, right? The neutral side of the transformer is just unbroken wire back to the N on the IEC?

Yes, is that kosher?

I can't get my head around the switching jack either. I've called a couple electronics stores and, while they do say that they think they have something that performs the switching function, they don't seem to be familiar with the term "switching jack". Is there another name for these? I've found "open circuit" and "closed circuit" 1/4" jacks, could one of these be it?

-AE

[buddy holly]

You're only using 2 pins on the power switch, right? The neutral side of the transformer is just unbroken wire back to the N on the IEC?

Yes, is that kosher?

I can't get my head around the switching jack either. I've called a couple electronics stores and, while they do say that they think they have something that performs the switching function, they don't seem to be familiar with the term "switching jack". Is there another name for these? I've found "open circuit" and "closed circuit" 1/4" jacks, could one of these be it?

-AE

AE,
Sorry, missed your querstion the first time. the jacks that i sent you with the strips are perfect for the job.
--BH

[phantom power]

Here's an update:

Last night I got the phantom power running. I had a little trouble at first and thought it was the way I wired the switch. I was picking up a radio station really clearly though. Then, I U'd the FSF a bit and found a Scodidly post that summed it up. The input xlr wasn't grounded. I did that and the signal was instantly clear (even more so than before I ever wired anything with the phantom). So now I've got Scott to thank as well.

So, why is grounding pin 1 on the input xlr an issue with a phantom powered mic and not a dynamic?

All that's left now is the DI and I still have to put the diodes in there to get down to 44V, then I 'll start working on the case.

Anyhow, here's a new question. What kind of switches will I need to use for replacing the phase, high-pass and mid-range eq? I assume that the phase switch needs to be an on/on dpdt (or is dpst better). I have no idea on the other 2.

Thanks -AE

[Nate Dort]

So, why is grounding pin 1 on the input xlr an issue with a phantom powered mic and not a dynamic?

If pin one is left floating and not tied to ground, then your mic cable becomes a big antenna and RF is probably amplified by the active electronics in your microphone.