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In Reply to: RE: Need some electrical help. posted by MannyE on November 04, 2016 at 20:53:09
OK!!One basic rookie mistake... I assumed it had fuses in it. It did not. This is why I was getting normal 120v readings from the female end of the IEC power cord but no power going through to the other side.
So I looked around to see if I had any fuses and luckily, I had some left over from my Bottlehead or Hagerman Cornet build. (Bottlehead and Hagerman both put every little detail on paper, so all I had to know how to do was solder and measure voltages according to the manual...easy).
125A/250V 5x20mm SLO-BLO fuses.. (a question about that will come at the end)
Put the fuses into the IEC module and set up a VERY DANGEROUS bench test with the leads going into the hot and neutral as instructed and the output leads on the rubber pad that I have covering the workbench.
Plugged the thing in and viola! 17.8 Volts off the black and red leads and 17.79 Volts off the orange and yellow leads.
It was a simple solution. Fuses.
Now comes the next issue. Encouraged by this excellent result, I turned the switch on and off a few times and measured to make sure it hasn't been a fluke. All is well.
I then proceeded to (after disassembling the whole deadly thing, the reassembling with the board) connect the red and black and orange and yellow to the board. Flipped the switch on, and measured at the blocks on the board, nothing. One of the fuses had blown.
I'm going to call it a night, and see about getting the correct connectors for the IEC pins. I don't want to damage it ($24) by overheating it with an iron later on, and for safer bench testing.
QUESTION... should I get different value fuses? Are those OK?
Thanks again everyone! I will post pictures and what the troubleshooting reveals.
Edits: 11/06/16Follow Ups:
125A/250V 5x20mm SLO-BLO fuses.
125 amp? I am pretty sure you mean 1.25 amp? A 125 amp 250V fuse is a pretty big fuse. Amperage as well as physical size.
I then proceeded to (after disassembling the whole deadly thing, the reassembling with the board) connect the red and black and orange and yellow to the board.
Are you 100% sure you hooked up the secondary windings correctly?
Did you parallel the two windings so they were in phase with each other? If not the two winding will buck one another and that would blow the fuse protecting the transformer.
Winding #1
Blk and Red leads.
Winding #2
Org and Yel leads.
To parallel the two windings,
Connect the Blk lead and the org lead together. (This becomes one hot leg of the 15Vac that will feed the board)
Connect the Red lead and the Yel lead together. (This becomes the other hot leg of the 15Vac that will feed the other terminal on the board.
Are you 100% sure you hooked up the secondary windings correctly?
Ah! No! I did not do that. I will try it as you say and report back. Since there were two blocks on the board to connect A/C I assumed it was one block for each winding.
Where is the schematic wiring diagram for the board? I wouldn't hook up anything to the board until you know for sure what's going on with the two AC terminal blocks.
Your neighborhood must be dark.
Do you mean 1.25 (1¼) amp? I'm going to assume that's the case.
That Schaffner filter you bought is rated at 1 amp, according to the label on the photo you posted, and according to the data sheet for that model number.
I'd use a 1 amp (or lower) fast blow fuse. If the circuit you're building draws more than one amp, you should have bought a filter rated more than one amp.
Good luck with your project.
Manny,
You noted the voltage and size of the fuse you tried, but not the amp rating. And I'm not sure what you mean by "one of the fuses had blown." There's only one fuse in the circuit. If there's a place to put another fuse in the fuse drawer, it's just a place to store an extra.
Since you're wiring the output of your transformer in parallel to get 15 volts, that particular transformer can draw up to 1.66 amps. So if you had a fuse rated at 1 amp or less in there, that could possibly explain it blowing, although there should be very little amp draw with no load connected to the power supply. Methinks there might be something else wrong, but check first and see what value the fuse was that blew.
Actually this thing has two fuses, one for each live connection. It has a fuse holder to house a third which is a spare.
I have a link to the data sheet. Look at page 5 at the bottom.
As far as the fuse goes, what should I look for at the store tomorrow? something in the range of 1.5 to 2 amps at 120 volts?
I'd recommend 1 amp, either 125v or 125/250v (rated for both). Get a few extra, as I'm not feeling all warm and fuzzy that the fuse rating of the one(s) you blew are the problem.Interested to see how this all turns out. I'm just starting a build on a power supply myself (from AMB instead of Booz). Like you, I'm competent with a soldering iron and have built a bunch of kits over the years. But this one required some parts sourcing on my own, and figuring out a few things that made me scratch my head initially (like LED dropping resistor values and transformer wiring). :) Hope mine doesn't blow up...
Edits: 11/06/16
bcowen,I see you deleted your previous post. Here is my response.
You are correct for the maximum current rating of the secondary. The data sheet shows for parallel, 15Vac, the transformer is good for 1.66 amps.
25Va/15V = 1.667 amps.For the primary winding you have to divide 25Va by 115V.
25Va/115V = .217 amp.Recommended minimum fuse size rating.
.217 X 125% = .27ampMaximum fuse size rating.
.217 X 250% = .543 ampI would not use a fuse bigger than 1/2 amp on the primary side feeding the transformer. As for why the 1.25 slow blow fuse blew my bet the OP shorted out the secondary windings by hooking them up wrong, or, he wired them in parallel out of phase with one another. Hopefully he didn't fry the transformer.
A 1.25 amp fuse would be about 575% of the FLA of the primary.
.217 X 575% = 1.25 amp
Edits: 11/06/16 11/06/16 11/06/16
You are right... I accidentally hooked them up parallel which blew the fuse.
Yes, I did delete that post. After Shovel's comment on the amp rating of the IEC filter, I went back and looked at the spec sheet. And looked at it wrong - I didn't pay attention to the fact that it was a general spec sheet for several different models. Shovel (and you) were right, I wasn't, and as nobody had responded at that point I deleted the post rather than add unnecessary confusion to the mix.
Thanks for the detail on the amp rating. I just learned something. I thought the fuse needed to cover the amp draw of the transformer secondaries, which is what I was basing calculations on for MY power supply. Looks like I need to go back and recalculate! Greatly appreciate the explanation.
bcowen,Thank you for posting the schematic diagram for the IEC/switch/fuse/filter unit.
http://www.audioasylum.com/audio/tweaks/messages/20/202695.htmlIt helped a lot, at least for me, to know what all the thing did.
I still wonder if the safety equipment grounding conductor travels/passes straight through the thing.
Also I would have never thought it had a double pole single throw power switch, DPST.
As for the fusing of both incoming lines. The schematic diagram shows a jumper through the fuse clip on the neutral Line. That indicated to me a fuse should not be needed on the 120V unit. A neutral should never be fused. It can be dangerous in certain circumstances. What I don't know for sure is what the OP has. He could just pull the fuse on the N, neutral, side and check for continuity across the fuse clips.
I believe the unit is designed to be used on 240V as well as 120V power systems. That would explain the DPST power switch and both hot AC power lines fused. The thing is the 240V mains would have to be both Hot ungrounded conductors. Maybe for a Europe 240V balanced power system...
Jim
Edits: 11/07/16
It is designed to go to 240V. Maybe the medical uses require 240? Dunno. Either way, it seems to be a great solution for plug, filter and power switch all in one.
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