My Rigol ds2202 power supply died

[Aido4ever]

Hello everyone.
My Rigol ds2202 power supply fuse was blown, after testing it I've found out that the PEA1522P PWM Driver was blown (Has a hole in it) and that the SM (Flyback) Transformer connected to it is burn-out. On the primary side one Coil has 40mega owms and the other ~2 owms, on the secondary side it has 0 owms.

the marking of the transformer is EF20B and it has an additional wire going out from its top side to the board (Thermal sensor?).

The varistor sitting next to the transformer is OK. I've ordered some ICs from aliexpress but I can't find the transformer anywhere, my guess it's a custom one.

I connected Rigol throw a local supplier and at first they claim that this power supply is obsolete and they only can offer me an upgrade (no thanks) and after some pressure, they claimed the found one but they ask 200 euros for it! 200 euros for simple SMPS, with this price I can buy 1000W high-grade power supply for my computer.

Help will be appreciated

[shakalnokturn]

Depending on how experienced you are it may be worth getting a couple more photos up including the under side of PCB.
That looks like a standby supply transformer.
0Ω (secondary?) and 2Ω (primary side feedback/PWM supply winding?) are probably OK if tested with a DMM.
What's the one measuring open meant to be? Primary winding linked to TEA1522P pin 8?

The floating wire off the top of transformer could be an intermediate tap or more likely a screen between primary and secondary.

If transformer really is dead you can rewind it, all it takes is the right wire and notes on disassembly.
The hardest part is removing the core without breaking it.

[Aido4ever]

Thank you for your kind help.
Here are some pictures of the backside of the board with the measures I took from the SM Transformer.

[shakalnokturn]

The 2Ω winding should lead to +300 or 400V somewhere, that would be the primary.

I assume the 41MΩ is not an actual value but more like what your meter displays when beyond range?

Can you check if floating wire ties to primary ground?Then measure between floating wire and transformer pin that goes to D203?
If that's in the 0-1Ω range transformer probably good...

[Aido4ever]

Correct, the floating wire is grounded.
And the resistance between the floating wire and the transformer pin that connected to D203 is 36M.

I just found out the secondary is outputting power to the fan connector.

[Aido4ever]

A picture that described the tracing from the Transformer secondary output to the FAN pin.

[shakalnokturn]

I think your open winding should be between the floating wire and D203, it would be used for the regulation loop through the opto, maybe to supply PWM, it also syncs the switching for transformer demagnetisation.

In the case of a blown PWM the winding usually fused open would be the primary between +300V and switch drain.
In your case if the AUX winding has fused there should be damage elsewhere. (D203, D204, opto...?)

If there are no signs of damage on these components I reckon that it is the open AUX winding the starting point that caused destructive loss of regulation.
Check closely at the transformer's pin (the one leading to D203) if the pin hasn't been slightly pulled out of the plastic and snapped the wire.
Am I right in assuming that this PSU is mounted sideways in the scope and that the transformer is on the top side?

[Aido4ever]

Thanks again.

D202, D203, D204, and optocoupler are OK.

[bdunham7]

That's disappointing that last year's model is obsolete, but this seems to be the new way.

I doubt you'll ever find the exact transformer for this.  If you can source a new core and maybe a new bobbin, you could take the transformer apart without worrying about damaging anything, and then repair or rewind a new one.  This might be a place to start looking for those parts:

https://xy-elelz.en.made-in-china.com/product/iocQHkGDHyUh/China-Ef20b-Ferrite-Core-for-Transformer.html

[james_s]

The transformer is almost certainly a custom part, you won't find a replacement off the shelf. You might get lucky and find the break though, look very closely at the place where the wire connects to the pin. As a last ditch effort something that I've done a few times is connect a low current source of a few kV between ends of a winding, turn that on in a dark room and look for the spot where it arcs. This is somewhat risky to the transformer though so try to locate the brake through other means first.

[Aido4ever]

That's disappointing that last year's model is obsolete, but this seems to be the new way.

I doubt you'll ever find the exact transformer for this.  If you can source a new core and maybe a new bobbin, you could take the transformer apart without worrying about damaging anything, and then repair or rewind a new one.  This might be a place to start looking for those parts:

https://xy-elelz.en.made-in-china.com/product/iocQHkGDHyUh/China-Ef20b-Ferrite-Core-for-Transformer.html

That's' oscilloscope cost me more than 2400 USD and to think they do not hold spare parts for it makes me think twice about from whom I'm gonna buy my next oscilloscope.

[bdunham7]

That's' oscilloscope cost me more than 2400 USD and to think they do not hold spare parts for it makes me think twice about from whom I'm gonna buy my next oscilloscope.

Unfortunately you may not get any more satisfaction anywhere else.  Where are you located?  There are laws in many jurisdictions mandating both warranties and availability of spare parts for a certain period of time after sale.  Their offer of a new PSU for €200 pretty much satisfies that obligation, I suppose. 

[shakalnokturn]

Thanks again.

D202, D203, D204, and optocoupler are OK.

Have you closely inspected where the wire wraps around that pin before entering the windings to check if it was cut there?

[Aido4ever]

All wires wrapped to their pins, there is just one pin without wire and this is the one I've marked as disconnected and this is the way it supposes to be.
Is that what you mean?

[shakalnokturn]

Yes.
So it looks like you're in for a rewind...
I've had luck unsticking ferrite cores by boiling the transformers in water, use gloves to pull on them while hot.

[Aido4ever]

I've tried yesterday to remove the tape from the transformer and it's very hard since the tape is inside the ferrite core. so you say I need to boil the transformer in water to make the tape come out? but what about the diameter and length of the wire, do I need to measure the diameter and count the loops or measure the length, or there is a better way of doing it?

[bdunham7]

I've tried yesterday to remove the tape from the transformer and it's very hard since the tape is inside the ferrite core. so you say I need to boil the transformer in water to make the tape come out? but what about the diameter and length of the wire, do I need to measure the diameter and count the loops, or there a better way of doing it?

The core is in two pieces shaped like an 'E', look at the link I posted if you haven't already.  If you boil it the glue that holds it all together may soften up so that you can pull the two 'E' parts away and the bobbin, tape and windings will all be accessible to work on.  Recovering the original ferrite core is ideal because even if you match them physically, their composition may vary.  The ones I linked will probably work if you can find them, but keeping your originals would be the easiest and best way.  Good luck. 

[Aido4ever]

Thank you for your reply and the link you posted yesterday. I did look at the website you linked and I saw a different plastic holders for the wire and ferrite core but I don't think any of them is the same as mine and there were no dimensions of them posted on the website.

Yesterday while trying to cut out the tape one of the legs have broken with a piece of the plastic holder.

[bdunham7]

Here's another, with dimensions.  I looked these up because I believe the 'EF20B' on yours refers to the generic core or core/bobbin assembly, not the actual specific transformer.

https://www.elelz.com/Ef20b-Ferrite-Core-for-Transformer-pd78939177.html

There's not much point trying to work on these without splitting the core.  Your bobbin simply looks like a 10-pin version with the outer 4 pins removed.

EDIT:  And here's your bobbin--maybe.

https://www.mycoiltech.com/ef20-vertical-bobbin-for-soft-ferrite-core_p1260.html

[shakalnokturn]

The tape over the ferrite (the one with the part number on) you can cut through of course.
I wouldn't try rewinding without removing the core, it's a lot of bother and if you start cutting at that tape you're likely to do more harm than good.
Removing the ferrite watch out for a plastic spacer between the two E's it has to be there.

Your broken winding may not be the first one accessible. With a bit of luck you may be able to reuse all the original wire.
The most important is to note the direction of the winding, well it's not the most important but it is the easiest to forget and get wrong later....
Of course the number of turns and wire diameter matter also.

[Aido4ever]

Here's another, with dimensions.  I looked these up because I believe the 'EF20B' on yours refers to the generic core or core/bobbin assembly, not the actual specific transformer.

https://www.elelz.com/Ef20b-Ferrite-Core-for-Transformer-pd78939177.html

There's not much point trying to work on these without splitting the core.  Your bobbin simply looks like a 10-pin version with the outer 4 pins removed.

EDIT:  And here's your bobbin--maybe.

https://www.mycoiltech.com/ef20-vertical-bobbin-for-soft-ferrite-core_p1260.html

Thank you very much, I'll look into it.

[Aido4ever]

The tape over the ferrite (the one with the part number on) you can cut through of course.
I wouldn't try rewinding without removing the core, it's a lot of bother and if you start cutting at that tape you're likely to do more harm than good.
Removing the ferrite watch out for a plastic spacer between the two E's it has to be there.

Your broken winding may not be the first one accessible. With a bit of luck you may be able to reuse all the original wire.
The most important is to note the direction of the winding, well it's not the most important but it is the easiest to forget and get wrong later....
Of course the number of turns and wire diameter matter also.

Thank you very much for your kind help.