I should preface this by saying I'm a complete electronics noob. Dave got me interested into electronics, and I've got just a very basic lab (couple oscilloscopes, a cheap multimeter and a decent Weller soldering iron). I'm trying to build up my "arsenal" of stuff.
I bought an HP E3610A from a flea market being told it worked just fine. When I got home, I heard a rattle inside. I opened it up and there was mounting hardware for the bridge rectifier and the transformer was installed upside down. It looked like someone had tried to fix it in the past, failed, and just threw it back together leaving it to be bought by me. I'd really like to get this thing working. I took some pictures.
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I resoldered (painstakingly) the transformer back on to the PCB (the leads were clipped, but there was just enough to reach). I remounted the bridge rectifier and applied some thermal paste and attached the heatsink. Tried turning it on, and nothing.
I (for some reason) unsoldered the transformer again to try to isolate it to check voltages...nothing. I then checked the pin-out of the AC jack, and one of the wires wasn't connected to anything (brown stripe in first picture). There was nothing connected to "hot" at all. This was weird because I saw dave's blog #166 with the same power supply, and the wires seemed to be soldered in the same locations. Anyway, I thought it was possible when someone tried to fix the scope, they got another AC jack that fit, but in reality had a different pinout, so I soldered the wire to hot. I plugged it in, hit the switch and my room browned out...I take it that's a bad thing (no, the transformer is not connected right now). Anyone have any ideas?
Beautiful pictures.
The are four wires on the power switch. The intention of the switch is to connect each of the two wires coming from the AC mains to one each of the two wires on the primary windings of the power transformer.
My best guess of what has happened is that you have connected the two AC mains wires across one side of the switch and the two transformer wires across the other.
When you activated the switch, you shorted out the AC mains through one switch connection and possibly damaged that side of the switch while also dimming the lights and possibly tripping a circuit breaker in your house.
However, on the other switch, the power transformer was shorted out, but since it was never, by this wiring arrangement ever connected at all to the AC mains by this connection scheme, it remains in a as a pristine and undamaged condition as before this mishap, so also that side of the switch.
My second guess is that you connected the switch wires correctly. but connected the secondary winding of the transformer to the AC mains and this is the cause of your overload.
Update me on your efforts and I will proceed further to troubleshoot this power supply with you.
I (for some reason) unsoldered the transformer again to try to isolate it to check voltages...nothing. I then checked the pin-out of the AC jack, and one of the wires wasn't connected to anything (brown stripe in first picture). There was nothing connected to "hot" at all. This was weird because I saw dave's blog #166 with the same power supply, and the wires seemed to be soldered in the same locations. Anyway, I thought it was possible when someone tried to fix the scope, they got another AC jack that fit, but in reality had a different pinout, so I soldered the wire to hot. I plugged it in, hit the switch and my room browned out...I take it that's a bad thing (no, the transformer is not connected right now). Anyone have any ideas?
Do you mean that the breaker for your room tripped?
It seems like the fuse in that AC jack was blown and that you bypassed it. That's not a good thing to do.
If there is still a short with the transformer removed when turning on the mains switch, it seems there is a problem with the wiring or alternatively the switch could be broken.
This is what I don't understand....
I measure 115 VAC between the grey stripe wire and the metal with no wire attached.
I don't measure any voltage between the brown/grey striped wire and anything. It doesn't even pass a continuity test with any of the input pins. I'm really confused.
My mains input is wired up the same way as Dave's....How is this thing supposed to get power if only the neutral is connected?
As megajocke pointed out, that socket is an IEC fused socket, so it has a fuse inside.
It seems like the fuse in that AC jack was blown and that you bypassed it. That's not a good thing to do.
Turn the power off and unplug the power supply.
Slide the door out from the IEC socket, take the fuse out from the back of the socket and check if it's blown.
Although this probably isn't the cause, it will help troubleshoot the problem.
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I take no responsibility for any injury, harm or damage you may incur trying to execute the above steps.
OOOOH Okay. I had no idea what he was referring to when I read his post, then last night I saw that there was supposed to be a fuse on the schematic, but I was looking all over for it on the board. It didn't even cross my mind that it would be in the input. I just found it, popped it off and saw that it was blown. I'll have to pick up a pack of these things (I feel like I'll go through a few of them).
Thanks!
Also, I did a continuity check on the switch and it appears to still be functional.
One thing that's concerning me right now is whether or not I'll blow my fuse by hooking up the transformer with no load. I mean...it's little more than just some magnet wire between the leads, so won't connecting those up to the input just short out my power? I guess I can just try it out (that's the name of this learning electronics game, right?).
One thing that's concerning me right now is whether or not I'll blow my fuse by hooking up the transformer with no load. I mean...it's little more than just some magnet wire between the leads, so won't connecting those up to the input just short out my power? I guess I can just try it out (that's the name of this learning electronics game, right?).
I would not suggest you try that. You may blow other components which would be a bad thing.
Others, more experienced than me will chime in soon and help you trouble shoot. Until then, trying things may cause more damage.
In the mean time, I thought I'd ask you a few questions and get a feel for what's happening.
In your first post when you said "soldered the wire to hot", which wires did you solder together? Can you show with a photograph or drawing?
Is it still soldered like this, or have you gone back to the way it was.
Once you've put a good fuse back in, you can perform some simple tests to determine if your power transformer is probably ok or shorted or you have some dangerous wiring condition existing that needs correcting before plugging this thing into the AC mains again.
With the power cord unconnected to the power supply and the AC mains:
(note: To learn to do all the tests I have suggested properly or to see this effect properly, try this test on a known good piece of transformer powered equipment...remember it is unplugged from the mains when you make this test!
First, set your DMM to the lowest ohm scale you have, or to the 0-1 or 0-1.999 ohm scale. Measure the resistance between the two AC mains pins on the 3-wire power socket. The green wire is the earth ground and the other two connections are the AC mains and are together above or below the ground wire third wire. You should see a quite low resistance, but be careful here to notice that the ohm meter will take some pause to attain a low-ohm reading than if you just connected both of your probe tips together..this pause time indicates probably your power transformer is good.
You may have to switch the power switch on the unit to get a reading. You should see an open circuit at one position of the on/off switch, the (ohms scale over range)
if the power switch is not connected or is not connected properly, you first need to get the switch circuit to work properly before any of the other test to work.
If you turn the power switch on and off and see a low resistance in both positions of the power switch, you have a wiring problem. If you turn the power switch on/off and you see always an open circuit, then the problem is not the transformer but the wires going to the transformer and the AC mains power connected to it and you probably have some dangerous wiring
Secondly, put your ohm meter on a high scale, mega ohms scale, and measure the resistance from either side of the power mains pins to the chassis ground, if you see any resistance lower than in the meg-ohms your transformer may be shorted to ground by wiring or an internal fault in the transformer and you need a new power transformer. If you disconnect the power leads to the transformer and toggle the power switch and still see a low resistance across the AC power pins or from either power pin to ground you have a dangerous wiring problem that must be corrected before playing again with the transformer.
Thirdly, if you verify no direct connection to ground (low resistance) from either AC mains power jack pin, you can make a good check of your transformer with your scope:
Connect your scope directly across the power pins (of course with the power cord disconnected! ) if you measured a low ohm or fractional resistance measurement across the power pins previously with an ohm meter. Use a 10x probe and set your scope input to Auto Trigger and about 100mS/sec time div and volts to 10V/div or so and trace free running.
Now take your ohm meter and set it to a diode-transistor test or ohms scale and touch the probes across the scope leads connected to each of the AC power pins the AC mains connector. You should see a short sharp HV spike as you quickly remove one or both of your MM probes on the low ohms scale. This indicates a good power transformer.
I've attached photos of the mains wiring from the IEC socket to the power switch on my E3610A. It's a 240VAC model, but the wiring should be the same, the difference being the mains transformer.
Comparing the pictures that the OP has posted, the wiring from the IEC socket to the switch looks correct.
Hope this helps with the ongoing troubleshooting.
Got it all wired back up and it wouldn't turn on.
I checked all the tests that Paul Price suggested
I looked and saw I didn't get the slow-blow fuses like I needed. I got the regular type (grr...the guy lied to me saying they were slow blow) Looks like I'll need to get some. A good note, however, is that for a brief moment before the fuse has blown, I saw the display turn on.
Hmm..what was the current rating of the fast-acting fuse just blown?
I assume you've soldered the transformer back into the circuit, or is it you have just the power line wires connected to it from the power switch and power connector?
Hmm..what was the current rating of the fast-acting fuse just blown?
I assume you've soldered the transformer back into the circuit, or is it you have just the power line wires connected to it from the power switch and power connector?
Yeah, it's soldered back into the circuit.
Hmm..what was the current rating of the fast-acting fuse just blown?
I assume you've soldered the transformer back into the circuit, or is it you have just the power line wires connected to it from the power switch and power connector?
Yeah, it's soldered back into the circuit.
The current rating was 2A 250V, but it wasn't the slow blow type. I'm guessing there's some kind of transient that occurs at power on that's much higher than 2A.
I should also note that when I bought it, the main full wave rectifier (CR2 in the schematic) was desoldered as well. I desoldered it, but I also bought another one yesterday just in case something was wrong with it. I haven't put it in yet.
You can measure (with all AC power disconnected) the resistance across the + and minus terminals of the bridge rectifier, it should read in the tens to 1000's of ohms if you place the positive lead of your ohm meter on the + pin of the bridge. It should take some small time to settle, and the readings should climb. If you meter does not have a diode-test ohm settings, use the lowest scale.
If the reading remains below 10 ohms and the meter doesn't slowly climb up in numbers, the bridge is likely shorted..or the largest electrolytic cap output filter cap the bridge connects directly to. You should also take readings from collector to emitter and collector to base and base of the two large power transistors sitting on their pedestals at this point. For each measurement, of each transistor, you take two readings, and you reverse the probe leads to make these two readings at the same point, that is between c-e, c-b, b-e.
Take some notes and let me know the news!