Weller WE1010 Stopped working and troubleshoot - Page 1
Forum section: electronics / repair

author: shkhamd
author_rank: Contributor
timestamp: January 09, 2019, 04:52:02 pm
content: Hi anyone using weller WE1010 soldering station?I have this unit (my mains is 220VAC 50Hz so I use it with a 220v-110v step down converter) and suddenly it stopped working.So I opened it up and did the following tests:1. transformer primary side shows 8 Ohm, secondary side shows 0.5 Ohm resistance2. Secondary Polyswitch and Fuse was good.3. At power applied, primary side has 100VAC 50Hz, secondary side shows 19VAC rms4. The onboard fuse on the PCB was also fine.5. But the 470 marked resistor ( R22, is it a 3 watt one?) on the attached picture shows a variable value roughly from 250 KOhm - 1M Ohm.6. The rectifier diodes(D4, D3) were good and forward voltage was 0.6V tested with my DMM.7. But the rectified DC voltage across the electrolytic cap showing around 2-3V, so obviously the 7805 voltage regulator was not supplying any DC current to the main controller.I have tried to reconstruct the rectifier circuit from the PCB traces.Please see the schematic picture I have added.I don't recognize either of the diode markings (729 ZHK and A4) , nor I found anything useful by searching them on google. there ar lot of diodes with similar markings.Also the diode rectifier part is a bit odd to me. Is it possible that D4 is a zener dropper in combination with R22 and the D3 is only acting as half rectifier?In that case R22 is damaged by an overcurrent (may be an unusual in rush or surge) condition makes sense to me ( just suspecting, I am not an expert on electronics).Also I don't understand why didn't the fuse tripped first in that case.So after all these tests my guess is the 470 marked resistor is somehow gone bad.But I am still confused to replace it with a good 47 Ohm with it because I m not certain about the root cause that made the resistor to fail.Any ideas anyone?

author: montarbo
author_rank: Contributor
timestamp: January 09, 2019, 05:23:11 pm
content: Hi,R22 in that package can in no way handle 3w. Change r22 with TH resistor and test if u r not getting any short to GND beyond the resistor.

author: Armadillo
author_rank: Super Contributor
timestamp: January 09, 2019, 05:26:38 pm
content: D4 is a 5.1V Zener part number SMAZ5V1.Edit; [Some Cal Error]The Design Current is 0.1A;The resistor heat up and failed with time. Edit The Voltage Drop across the Resistor is 5V at 0.53W

author: shkhamd
author_rank: Contributor
timestamp: January 09, 2019, 06:08:07 pm
content: I m deeply disappointed with weller, their design choices are so bad, how many cents they saved from not using a full bridge rectifier ic with a big TO220 package of 7805 ( 2 parts instead of 4 parts).The total current of the microcontroller, LCD and MOC opto should not cross 100mA in ideal condition, since the controller circuit is just a specialized dimmer circuit with a BTA12 triac.Anyway, I dont have 3watt zeners but I do have 1watts.Can I use 3 1watt zeners in parallel?One more thing, The zener voltage is a bit confusing.Why it has to be a 5.1V zener? 19VAC rms becomes around 25V at peak, so a drop of 5volt is still 20volt acrosa the 7805.So to drop 15 volt on the 7805 input the dissipation at say 200mA becomes 3watt.Sent from my Nokia 7 plus using Tapatalk

author: wraper
author_rank: Unknown
timestamp: January 09, 2019, 06:12:49 pm
content: Quote from: montarbo on January 09, 2019, 05:23:11 pmWhy would it need to handle 3W?

author: wraper
author_rank: Unknown
timestamp: January 09, 2019, 06:22:41 pm
content: Current consumption should be tiny, well below 50mA. And 47uF capacitor with a half bridge rectifier is a good indicator for that. There are no signs of overheating on resistor itself or PCB around it. Most likely it failed due to mechanical reasons. Largish SMT parts are sensitive mechanical stress. Also it might be just a crack in solder joint. Picture is not close enough to see how solder joints look like, though.

author: wraper
author_rank: Unknown
timestamp: January 09, 2019, 06:27:10 pm
content: Quote from: shkhamd on January 09, 2019, 06:08:07 pmUsing full bridge rectifier won't add any reliability. There is no need for vreg in TO-220.

author: Armadillo
author_rank: Super Contributor
timestamp: January 09, 2019, 06:29:46 pm
content: I think your comment was a result of my earlier wrong cal which has been corrected. Please read the updated one above. ThanksQuote from: shkhamd onTodayat 05:08:07 am

author: shkhamd
author_rank: Contributor
timestamp: January 09, 2019, 06:33:48 pm
content: Quote from: Armadillo on January 09, 2019, 06:29:46 pmyes, didn't see the updated reply Sent from my Nokia 7 plus using Tapatalk

author: shkhamd
author_rank: Contributor
timestamp: January 09, 2019, 06:38:15 pm
content: Quote from: wraper on January 09, 2019, 06:27:10 pmactually I m curious why it needs a zener dropper at the first place?Can't a sub 100mA current draw easily be handled with the 7805 from 25V rectified DC?Sent from my Nokia 7 plus using Tapatalk

author: wraper
author_rank: Unknown
timestamp: January 09, 2019, 06:44:41 pm
content: Quote from: shkhamd on January 09, 2019, 06:38:15 pmThey just distributed heat over several parts. And there will be more than 25VDC when powered from 120V AC, getting very close to 35V absolute max rating and not having any room for increased mains voltage.

author: Armadillo
author_rank: Super Contributor
timestamp: January 09, 2019, 06:50:53 pm
content: The 7805 will heats up. In Good Design, it is +3V to limit voltage drop across 7805. So 5V + 3V so that the 7805 will operate properly.You may consider the LDO type where the +3V can be reduced much more, say + 1.2V.Quote from: shkhamd onTodayat 05:38:15 am

author: KL27x
author_rank: Super Contributor
timestamp: January 09, 2019, 06:51:20 pm
content: 5V 100mA from a 25V input using a linear regulator is 2W. It would be silly to dissipate that much heat in a TO-220 part, IMO. If you want to use a linear regulator, get rid of some of that voltage drop in a power resistor. This is much more reliable than sticking heat sinks on the regulator and crossing your fingers. This is like taking a honda civic and putting in a 10.0 liter V8, but using it to generate 90% heat and 10% power.I've stuck a D2PAK 7805 on a 20V rail to power 20mA. Just an indicator LED and a microcontroller, so I figured it would be ok to be lazy. This was plugged in 24/7. It worked a couple of years before it died. Come to think of it, I also had a heatsinked TO-220 7805 on a 20V rail powering just a panel meters and a couple micros. When not in use, the panel meter was turned off, so it was really just a couple micros on there sipping power. There were a few holes drilled in the enclosure over the heatsink, but no fan. The regulator died in about a year or two. As I recall, it died at least twice, which is why I added the heatsink and the holes.. and eventually learned to use a series power resistor. 2W is nothing to a resistor that is happy to continue working at 70C, indefinitely. It is a lot to an IC.I vaguely recall someone trying to explain to me why this is bad, like 12 years back, at the time I did such things. That dropping 10's of volts in a linear regulator is not ideal, and the regulator might flake out years down the road. Well, I had to learn the hard way, but at least only on one-off stuff that was easily fixed.Wraper is on point on all his posts. FWIW, the Hakko 888 also uses a half-bridge for the control circuitry.

author: floobydust
author_rank: Super Contributor
timestamp: January 09, 2019, 09:37:33 pm
content: It's the possible high mains voltage due to the isolation transformer, when the heater is off, the voltage would go above 120V and overloaded R22 or C2 is damaged. But Dave did test that...R22 and C2 do see very high peak currents.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 06:08:42 pm
content: Okay guys, new update.I have replaced the R22 resistor with a 3watt 47Ohm one, the D4 zener diode with a 1N4733.Its now working fine, for at least the few minutes I have kept it under observation. I will have to wait for a longer stress test until next week.Now my observation is I measure 116VAC rms at primary,25VAC rms at secondarybut 44VDC across the IN and GND of the 7805!!!The drop across the zener is 1V in DC mode of my DMM!!!the drop across the 47 Ohm resistor is also less than 1V in DC mode of my DMM!!!But the output at the 7805 is as usual, 5V DC.I am not sure what's happening there but the the display and temperature controller is now working as before!Is it possible that I measured them in some sort of wrong way?Sent from my Nokia 7 plus using Tapatalk

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 06:24:30 pm
content: Quote from: shkhamd on January 10, 2019, 06:08:42 pmQuoteThat means current is tiny, around 20mA, just as I said before. Power dissipation is only 20mW. As I said resistor failed not because of overheating. And the only thing 3W resistor would do is rip the pads off.QuoteWhy would you do this? Likely you replaced it with zener rated for wrong voltage. And likely placed it in wrong direction on top of that.There shouldn't be 44 VDC so probably you made measurement wrong.All you have done overall is significantly reduced reliability.

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 06:25:22 pm
content: Better Diode Mode Check D3 whether its damaged e.g. shorted.

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 06:32:38 pm
content: BTW all of those who suggested modifications without even knowing actual current consumption and heat dissipation. IMO you should be ashamed for suggesting something that can lead to more damage without any valid reason.

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 06:58:30 pm
content: The only possible cause of your weird measurement result is D3 is not rectifying.You should measure it out of circuit to be sure, if in circuit measurement confused you.Or just replace D3 for double assurance.BTW, you sure your modification to higher wattage, you can close the enclosure?

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 07:09:31 pm
content: Quote from: Armadillo on January 10, 2019, 06:58:30 pmJust put everything as it was originally and don't do any further nonsense.

author: floobydust
author_rank: Super Contributor
timestamp: January 10, 2019, 07:15:18 pm
content: L78M05is rated max. 35V inso measuring 44VDC is bad news. Is the new zener shorted or what is the transformer secondary voltage.DMM measurements can lead you on goose chase because the voltage is DC with 1/2 wave ripple.Also you need true RMS to measure ACV because there is lots of sine-wave distortion with cheap transformers. It's rated 23VAC under (heater) load and 31VAC is what you are getting at no load (to maske 44VDC) but you measure 25VAC?The entire board is low power, I would guess 25mA with opto on. You can go through the math, but the Vreg must get much lower DC input.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 10, 2019, 08:15:56 pm
content: I can't help but wonder if the Zener was mounted in reverse, where it would simply drop its 0,6~0,7V instead of the rated 5,1V.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 08:44:41 pm
content: Okay rewinding what I have done so far:1. I have replaced the bad 47 Ohm resistor which I believe is obvious, may be overkill but should not hurt the circuit.2. I have replaced the D4 with a 1N4733, things that I could do wrong with it is, place in reverse polarity or use a wrong voltage value.Well, I have so far triple checked its polarity for being in correct orientation. I measured the forward voltage in diode mode and made sure that both the original and replaced diode shows the Vf from the same side of the PCB pads. Only difference is the diode original had Vf about 0.6 and 1N4733 has Vf about 0.7.I don't know how to check for the zener voltage.With the original SMD zener diode, the black terminal of the zener placed now was the pad where the cathode was and the other side was the anode.So in my present replacement it is still the cathode as you can see in the previous pictures.Shouldn't the positive voltage be applied at the cathode to make it act as zener, not sure if my understanding of zeners is wrong.Now is it possible that a zener diode may be damaged in such way that it will show it Vf just as a normal diode but when placed in circuit in zener configuration, it will act as a short?3. I also did checked the Vf of D3, the rectifying diode both in forward and reverse bias. Vf was 0.6V and in reverse bias it showed nothing or out of range for as if it was a very large value.So i believe D3 is also good.Edit: And I also powered the board up once and first I replace the resistor with the original diode still in it, it worked but I didn't take any measurement of the voltages though. Reason I replaced it later because 1N4733 is rated at 1watt.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 08:49:48 pm
content: Yes I also checked first if the housing can contain the resistor with in it and fortunately there was quite enough space under the front cover.Sent from my Nokia 7 plus using Tapatalk

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 08:58:52 pm
content: Take a meter, check the trace from the Resistor, which pad it goes to, then that pad should be connected to the cathode.The picture is not clear to see the trace from here.

author: floobydust
author_rank: Super Contributor
timestamp: January 10, 2019, 09:11:22 pm
content: I think your parts are OK, it's just the one DMM measurement 44VDC (VIN-GND tab) on the voltage reg. that is alarming.I'm trying to see why the DCV is so high when it shouldn't be, I think your multimeter might be wrong or..What PCB point are you using as ground for measurements? There is another component between PCB GND and the transformer leg. I don't show transformer connector pin 3 going to PCB GND right away... Pin 1 is safety ground.Your first post says 100VAC in, 19VAC out and now it is 116VAC in and 25VAC out which is not consistent.Any measurements on R22, zener, diode etc. are all pulsing DC so an oscilloscope is what you need to really measure properly. A DMM will not give good numbers with pulsing DC.Rough math, R22 power is 0.23W average and pulsing 1.5Wpk but at power-on it has much higher inrush until C2 is charged. I think R22 died of stress (it's a size 2010?), although for Dave's 240V experiment it just got a little discoloured and did not open circuit in the few seconds of transformer smoke.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 09:13:07 pm
content: Quote from: Armadillo on January 10, 2019, 08:58:52 pmYes did it at the first time. Please see my attached picture.All the things you guys mentioned here I have already checked them. The only thing I can't be sure about is my strange readings because I didn't triple check them or may be I was taking the reading in wrong way.Sent from my Nokia 7 plus using Tapatalk

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 09:17:34 pm
content: Quote from: shkhamd on January 10, 2019, 08:44:41 pmIt has no mechanical strength. Bump solder station against a table and resistor will fly off together with pads it is soldered onto. The best solution is to return everything as it was out of the factory. Resistor did not fail because of overheating, period. There is a mounting hole and rubber switch nearby to it. Therefore there will be mechanical stress/bending in that area of PCB, especially when button is pressed. And larger ceramic SMT components are prone to failure from mechanical stress.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 09:27:16 pm
content: Quote from: floobydust on January 10, 2019, 09:11:22 pmYes, standard voltage here is 220V and unfortunately its never stays rock stable here. Sometimes even as low as 180V, sometimes barely near to 220V. Its a shame. I use a 220 to 120V step down converter like this one:https://www.amazon.com/World-Travel-Plug-Power-Converter/dp/B07C1LPMRQ/So far yesterday was my first time attempt to figure out the damage and it's possible reasons. At that time measured everything from the primary to secondary and all other readings.Today also I measured the primary, secondary and all that. So its possible that the voltage are different since they taken in two different days.Don't also ask about my DMM, its a super dodgy Aneng 8008 one but anyway I tried to make the most out of my options. Sent from my Nokia 7 plus using Tapatalk

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 09:31:49 pm
content: Your connection of the zener is correct in that case.So where did you get the zener, is the part number correct and only to verify it is to test it. see attached.if you don't have the power supply, in that case, put back the old zener so that you can verify the circuit again.

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 09:35:58 pm
content: Just forget about that zener. Return original zener back where it was, problem solved.

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 09:37:41 pm
content: Better read the WARNING message from the adapter. I don't think is a normal isolation step down transformer in there. Probably just a resistor inside.its for hair dryer rated above 25W

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 09:39:18 pm
content: If you have so much excitement about modifying things, first make original thing working, then make measurements, then decide if it's even worth to modify anything. At least you will have baseline of how circuit should perform.

author: glarsson
author_rank: Frequent Contributor
timestamp: January 10, 2019, 09:40:00 pm
content: Also investigate what kind of problems are caused by that cheap and nasty 2000W universal "step down" converter.

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 09:42:33 pm
content: cannot use from 0 to 25W!

author: floobydust
author_rank: Super Contributor
timestamp: January 10, 2019, 09:44:47 pm
content: I thought it was a 240-120V "transformer", now it's one of those triac power halfers?There's the problem... Why not buy a 240VAC station in the first place?

author: glarsson
author_rank: Frequent Contributor
timestamp: January 10, 2019, 09:47:24 pm
content: Exactly. The sodder station doesn't draw much at all when not heating.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 10, 2019, 09:48:39 pm
content: Quote from: floobydust on January 10, 2019, 09:44:47 pmExactly. The waveform on the output of these converters is very non linear and should not be used with inductive or capacitive loads. They work very well for resistive loads.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 09:50:44 pm
content: Quote from: wraper on January 10, 2019, 09:39:18 pmIts not excitement for me (well may be to some degree it is, but not primarily), its necessity since its my only primary station.Yes, I did exactly made the original thing work by replacing only the resistor, but before I do that I posted here to reconfirm my understanding of the problem.Quote from: wraper on January 10, 2019, 09:39:18 pmI did not made measurements of the different test points after the R22 replacement, but only after I also replaced D4.May be that was not ideal but I m not sure either what you point as reliable here, the resistor died, that was not reliable at the first place too.Sent from my Nokia 7 plus using Tapatalk

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 09:52:52 pm
content: Please stop for a while before the LCD controller is damaged.I think the zener is fried again.Do get the isolation type step down transformer first.

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 09:54:13 pm
content: Quote from: shkhamd on January 10, 2019, 09:50:44 pmThere are such things like random failures. If some part failed, it does not necessarily mean it was overheating, stressed or whatever. I say based on my experience that what you have done is less reliable than what it was originally. And as it turns out, thing was not even powered properly.

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 09:56:53 pm
content: Quote from: Armadillo on January 10, 2019, 09:37:41 pmI think I found the reason, I m gonna tear it down and see what's inside that crappy thing.Should have used an actual 220v to 120v Isolation transformer at the first place.[hitting head on the wall]Sent from my Nokia 7 plus using Tapatalk

author: shkhamd
author_rank: Contributor
timestamp: January 10, 2019, 10:00:15 pm
content: armadillo and wraper, thanks guys, lesson taken.I was only thinking about the station never for once about the converter.Sent from my Nokia 7 plus using Tapatalk

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 10:02:56 pm
content: Quote from: shkhamd on January 10, 2019, 09:56:53 pmYou don't need isolation transformer. What you need is autotransformer. Single 230V winding with center tap (often called step-down transformer).

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 10:06:22 pm
content: That is the worse advice I heard.When the current is mA, the voltage is going to be 230V.same kind of shit.Quote from: wraper on January 10, 2019, 10:02:56 pm

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 10:11:31 pm
content: Quote from: Armadillo on January 10, 2019, 10:06:22 pmDo you even understand what autotransformer is?https://canadatransformers.com/what-is-autotransformer/QuoteIt works just like regular transformer but does not provide isolation. The advantage is it can be much smaller and cheaper for the same power.

author: glarsson
author_rank: Frequent Contributor
timestamp: January 10, 2019, 10:13:13 pm
content: Quote from: shkhamd on January 10, 2019, 10:00:15 pmAlready forgotten. :-(

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 10:22:07 pm
content: When the current approaches zero  the voltage rise.yourself.Quote from: wraper on January 10, 2019, 10:11:31 pm

author: glarsson
author_rank: Frequent Contributor
timestamp: January 10, 2019, 10:28:07 pm
content: Will the current through the Weller transformer primary be enough?

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 10:30:44 pm
content: When the heater stop, that's where the problems return just like the adapter he used.Quote from: glarsson on January 10, 2019, 10:28:07 pm

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 10:31:42 pm
content: Armadillo, that's some first grade BS written on that screenshot. Anyone who understands how transformer works will understand it immediately.https://youtu.be/XgVxbjmdJ7s

author: Armadillo
author_rank: Super Contributor
timestamp: January 10, 2019, 10:38:14 pm
content: Wraper, you can bullshit for all you want.But when your advice post a danger to the young learner, then you should jolly well wake up.!When the reactance is lower than the resistance of the wire, the voltage rise up to the destruction of the sensitive electronics.Where such possibility exist, then the advice is BAD.Don't act clever, we all know where you are.Quote from: wraper on January 10, 2019, 10:31:42 pm

author: glarsson
author_rank: Frequent Contributor
timestamp: January 10, 2019, 10:38:43 pm
content: Quote from: Armadillo on January 10, 2019, 10:30:44 pmProve it. If you are right then a variac would act like this - and they don't when I use them.

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 10:42:31 pm
content: Quote from: Armadillo on January 10, 2019, 10:38:14 pmIt's not danger, it's common knowledge. If you are clueless about the topic, does not mean others are. Transformer doesn't stop to be a transformer when there is no load. Only someone completely clueless would write something like this. Go the the link I provided before, ar read that. Not this BS you did tot even provide a link for. "Stopping transformer action", what this even supposed to mean? If this was true, center tapped usual transformers would not exist.

author: wraper
author_rank: Unknown
timestamp: January 10, 2019, 10:49:21 pm
content: Armadillo, don't bother. Read the comment from where you copied it.https://www.electronics-tutorials.ws/transformer/auto-transformer.htmlQuoteAnd then there is the comment by the author about that it was not about lack of load but if transformer fails and winding is interrupted. It just was written in ambiguous language.Quote

author: Armadillo
author_rank: Super Contributor
timestamp: January 11, 2019, 12:18:45 am
content: See attached;V2 = I1 * V1 / I2.Hence when I2 Reduces V2 Increase.[In practical, I1 must include magnetizing current and core losses etc.]Imagine autotransformer is 2000VA for example.Hey....I'm busy now.......

author: wraper
author_rank: Unknown
timestamp: January 11, 2019, 12:26:14 am
content: Quote from: Armadillo on January 11, 2019, 12:18:45 amYeah and you just highlighted transformation ratio, LOL.

author: Armadillo
author_rank: Super Contributor
timestamp: January 11, 2019, 12:47:42 am
content: just rush back to add that;In a dynamic situation is even worse, when I1 and I2 is high and suddenly I2 ceased to flow example heater cut-off. It's like you being run over by a lorry with heavy loads.In vacuum cleaner, hair dryer, I have no qualm with you.In sensitive electronic especially the situation OP is facing now, I will advice against it.OK busy....

author: wraper
author_rank: Unknown
timestamp: January 11, 2019, 12:57:02 am
content: Quote from: Armadillo on January 11, 2019, 12:47:42 amBusy enough to not switch your brain on. In previous post you attached example which shows that it works just like usual transformer but still continue splurting nonsense.QuoteIt will cease to flow as well. Transformation ratio goddammit. Look at what you highlighted.

author: Armadillo
author_rank: Super Contributor
timestamp: January 11, 2019, 01:00:44 am
content: Lousy Loser. Read #51.hahahahahahahaha

author: wraper
author_rank: Unknown
timestamp: January 11, 2019, 01:05:24 am
content: Quote from: Armadillo on January 11, 2019, 01:00:44 amI would just assume you enjoy embarrassing yourself.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 11, 2019, 02:11:01 am
content: Armadillo, consider connecting the primaries of two 110V transformers in series and then connecting the top and the bottom terminals to a 220V outlet. Do you really think you will have 220V in the middle terminal as well?

author: Armadillo
author_rank: Super Contributor
timestamp: January 11, 2019, 03:00:11 am
content: Hey, I am not good at academic type reply but ask you, when you open up electronic equipment, you find isolated transformer inside or wraper Auto-Trans inside?Common Sense question. Auto-trans is cheaper but?You think symetrically but in reality the load is single ended where I2 is part of I1 and the other half is I1-I2, so in practice it is not symetrical static type balance analogy. The induction in one is not the same as the other. The transients are not the same dynamically.The point is isolated transformer is VA limited and Auto-Trans is Grid KVA limited.If you mistaken the point, please read #51. But if you are still not satisfied, please derive your proof of academic formulation and scientific derivations so that others can appreciate your logic.Ok busy, subject ends for me. thanks.busy...bye.Quote from: rsjsouza on January 11, 2019, 02:11:01 am

author: wraper
author_rank: Unknown
timestamp: January 11, 2019, 03:34:15 am
content: Quote from: Armadillo on January 11, 2019, 03:00:11 amDo you connect all your 230V equipment to mains though isolated transformer?QuoteBut what? If you don't need isolation, then why would you pay for it with money, size and 3x weight? You already have isolation transformer within the device.QuoteIsolated transformer can have power of megawatts, it's just larger, more expensive and less efficient than autotransformer.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 11, 2019, 04:05:22 am
content: Hey Armadillo, don't deflect. You are the one doing a bold claim and has the burden of proof. What that statement and you are claiming is not practically verified, unless there is a fault on the transformer windings (and that is what it seems the subject of the further discussion pointed by wraper).You seem to reply a lot for someone that claims to be too busy. Oh well...