Enermax EG465AX-VE(G) Thermistor

[olliisit]

I have a Enermax EG465AX-VE(G) // FMA -II Series Power Supply

The Primary MOSFET dies and also destroys the Thermistor.

I am searching for circuit Diagramm ,

or Value of the Primary Thermistor (Postition Number:THR1) / Type: SCK...

The Missing Numbers on the Thermistor are burned Unreadable

Thanks.

[kaboom]

Re: Enermax EG465AX-VE(G) Thermistor

How big is the fuse?

If the MOSFET is shorted, make sure you check the IC that drives its gate.

You may want to use something like a 10 ohm 25 watt resistor in place of the NTC temporarily, to keep from blowing up thermistors. If you can, measure the size of what you have left, and look in the pdf for anything similar sizewise.

Room temp resistance won't be too high though- something like an SCK2R55 (2.5 ohm at 25c, 5A) from another power supply should work.

[momaka]

Re: Enermax EG465AX-VE(G) Thermistor

something like an SCK2R55 (2.5 ohm at 25c, 5A) from another power supply should work.

Agreed. If you have some spare junk power supplies, this would likely work fine.
If not, then look for a NTC (negative temperature coefficient) thermistor with similar specs to what kaboom posted above.

[PCBONEZ]

Re: Enermax EG465AX-VE(G) Thermistor

Enermax had issues with conductive glue not to far back.

https://www.badcaps.net/forum/showth...t=Enermax+glue

[olliisit]

Re: Enermax EG465AX-VE(G) Thermistor

Thank you all for your suggestions.

I will try when I have the Spare Parts.

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

I guess you did not fix this unit

I've already invested some time and components into this one so it would make sense to make it running, plus it is rather decent unit.

Well, I got this one with blown fuse and shorted primary switcher - there is only single FET, 12 A/800 V. Replaced that (with IPW80R360P7XKSA1), stand-by is OK. Turning it on with PWR_On with series light bulb resulted in a click (as it turns on - there is no relay) and bulb going immediatelly to full brightness. Now both the PFC diode and switcher (2SK2698, 15 A/500 V) shorted. Replaced diode and the FET temporarily with 18N50.

Now when I turn it on, the same, only that the components survive and do not go shorted right away, rather than there is a short just each time the main power supply (and PFC section) goes on indicated by the light bulb, but goes off when I remove the clip grounding PWR On.

The PWM driver is a UC3842BN, PFC is a UCC3817A with LM393 on a daughterboard. Which one to check first?

[momaka]

Re: Enermax EG465AX-VE(G) Thermistor

The PWM driver is a UC3842BN, PFC is a UCC3817A with LM393 on a daughterboard. Which one to check first?

Since you have separate APFC and main PWM controllers, I think it might be possible to troubleshoot it by removing the APFC diode and MOSFET first. If you still get the same symptoms, then it's definitely the UC3842b IC and/or the Gate drive circuit of the main switching FET (if there is one). Of course, you should check if the UCC3817A chip also disables the UC3842 when the APFC voltage is low (due to disabling the APFC).

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

I think only replacing the PFC FET with wire jumper should be enough, the diode conducts, the thermistor also does…however question is what will the PFC controller do without it? There may still be some reaction on the PWM fault sensing. But yeah, I guess it's worth testing.

[momaka]

Re: Enermax EG465AX-VE(G) Thermistor

If you put a jumper across the PFC FET, you're going to get a short-circuit between (+) and (-) busses on the primary side after the bridge rectifier. However, I forgot to mention: you should put a jumper across the PFC diode (or you can leave the diode if you like too).

If the APFC controller is unhappy due to removed FET, see if there is a way to mess with the voltage feedback circuit so that it "thinks" the voltage across the primary cap(s) is already boosted and normal. May need to read more into the datasheet for that, of course.

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

Right! I thought, for some reason, that the FET passes the current through. But it pulses in parallel with the cap. So just remove it and leave it be.

[kaboom]

Re: Enermax EG465AX-VE(G) Thermistor

Right! I thought, for some reason, that the FET passes the current through. But it pulses in parallel with the cap. So just remove it and leave it be.

It does not. It pulls the end of the boost inductor to input B-, after the line rectifier.

When the PFC controller turns its MOSFET off, the end of the inductor flies up and the PFC diode dumps this energy into the "boost" electrolytic.

If the PFC MOSFET is jumped out, you'll make that PSU go kaboom.

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

I got the general idea, just never really checked how it was actualyl wired. According to the schematic it is in parallel though (well, in front of the diode which blocks the current from flowing back when the cap is charged higher).

[sadmed]

Re: Enermax EG465AX-VE(G) Thermistor

Hello!

I have a PSU for a medical PC that's a modded Enermax EG651P-VE. Basically someone forgot to switch the transformer setting to 230V and it blew multiple components. The supply is custom and impossible to find a replacement for. If anyone has a schematic for it or a similar PSU, I would be seriously grateful!

Thanks.

Sid

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

Got yur message. I don't have any schematic for any PSU I've ever worked on, but it looks like pretty ordinary ATX PSU, what's custom about it?

If you are in the US, switching to 230V setting should do nothing, the unit should just not start. With such setting it does not double the voltage so it will get 190 V DC or so after rectification. Unless it was trying to run anyway and saturated core or something.

Trouble is with 115V setting on 230V circuit as that results to about 760 V DC.

[sadmed]

Re: Enermax EG465AX-VE(G) Thermistor

Got yur message. I don't have any schematic for any PSU I've ever worked on, but it looks like pretty ordinary ATX PSU, what's custom about it?

If you are in the US, switching to 230V setting should do nothing, the unit should just not start. With such setting it does not double the voltage so it will get 190 V DC or so after rectification. Unless it was trying to run anyway and saturated core or something.

Trouble is with 115V setting on 230V circuit as that results to about 760 V DC.

Yes, exactly. The supply was set to 115V setting and connected to 230V. The partial schematic you posted above resembles the PCB of the PSU I'm working on. Do you by any chance have the full schematic for that model? That would be helpful. Thanks!

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

Where did you get 230 in da US? The drier outlet or what?

Usually it takes the varistors which sometimes protect the rest. If not, than check bridge rectifier, PFC diode (and the return diode), PFC FETs and switchers and PFC/PWM controller driver (may be combo chip).

That drawing is reference circuit from the controller datasheet, nothing specific.

[sadmed]

Re: Enermax EG465AX-VE(G) Thermistor

Where did you get 230 in da US? The drier outlet or what?

Usually it takes the varistors which sometimes protect the rest. If not, than check bridge rectifier, PFC diode (and the return diode), PFC FETs and switchers and PFC/PWM controller driver (may be combo chip).

That drawing is reference circuit from the controller datasheet, nothing specific.

Oh, ok. The system is an international mode and usually takes 230V and to test and work on it on the bench switched the supply to 115V setting. He unfortunately forgot to switch the setting back to 230V on the supply when finished and it was sent to the site like that. The result was that it did take out the varistor, a capacitor and a power resistor. The varistor and capacitor disintegrated beyond recognition and I don't know the exact specs on them. I can infer, given common designs etc but for medical-related equipment, we need it to be an equivalent or exact part.

[Behemot]

Re: Enermax EG465AX-VE(G) Thermistor

IC, kinda a wonderer unit than.

In circuits with voltage doubler, the varistors are usually accross each cap so that'd be about 150 V AC or so nominal. Basically the lower the voltage above nominal for the varistor, the better chance it will act and protect the equipment in case of spike occuring.

But it must not be too low to act under more or less normal conditions. Including tolerance of the wall power voltage etc. So when there is 115 V nominal accoss a cap, they put aprox. 150V MOV there (which acts at about 180 V).

What was the cap? A ceramic, film…?

[sadmed]

Re: Enermax EG465AX-VE(G) Thermistor

IC, kinda a wonderer unit than.

In circuits with voltage doubler, the varistors are usually accross each cap so that'd be about 150 V AC or so nominal. Basically the lower the voltage above nominal for the varistor, the better chance it will act and protect the equipment in case of spike occuring.

But it must not be too low to act under more or less normal conditions. Including tolerance of the wall power voltage etc. So when there is 115 V nominal accoss a cap, they put aprox. 150V MOV there (which acts at about 180 V).

What was the cap? A ceramic, film…?

I really appreciate your responses! Thanks. Sorry, he just gave me the specifics. A capacitor was damaged but did not disintegrate - it was a 1200uF aluminum electrolytic. An MOV and a power resistor disintegrated.

[sadmed]

Re: Enermax EG465AX-VE(G) Thermistor

It's just a tricky situation. Basically we found the supply of the same part number and are getting a couple overnighted. If the PSU is identical except for the mods commissioned by the OEM, we will attempt to repair the old one first. If for any reason we can't do that, we will have to modify one of the new supplies or have a third-party do so. We have been trying to locate an entire PC that it could be harvested from, but to no avail as of yet.

Thanks again for your help!