Altec MX6021

[CapLeaker]

Re: Altec MX6021

The light bulb trick only works with the old incandecent tye light bulb. It doesn't work with CCFL's or LED type bulbs. The lamp is connected in series on the phase. If the bulb is hooked up in parallel like normal, it will not work as intended either. In order to determent if there still is a short on the primary side of the PSU, did you actually test the output on the secondary to see if there is any voltage coming out?
That little IC is the PWM that connects to the gate drive circuit to the FET. IF the FET was shorted to the gate, then you would have to inspect he gate drive circuit closely and probably replace the PWM. All you can do here is to check all components of the gate drive circuit, check the FET itself, do the lamp test, if there is still a problem, replace the PWM. I use a oscilloscope and a isolation transformer to see if the FET is switching or not. You can check with a DMM if the PWM is getting any power. The PWM also has protection built in, so you'd have to download the spec sheet and measure voltages etc.

[zerbino]

Re: Altec MX6021

Series) Lamp with nichrome coil)
Thanks, i will try)

[CapLeaker]

Re: Altec MX6021

Yeah, the old 100W glowing wire type A19 light bulb. Wire it up like in the picture on the phase wire.

[zerbino]

Re: Altec MX6021

as i told at 20 post it give light permanently. Unfortunately my knowledge is not enough except to replace U1.

[CapLeaker]

Re: Altec MX6021

see if there is a short at the main filter cap

[Behemot]

Re: Altec MX6021

Be sure it is discharged first. Altough a meter will indeed show charged cap as shorted, a one without input protection will most likely do that as the last thing ever

[naveenbedre]

Re: Altec MX6021

What is U1 specification number part number

[zerbino]

Re: Altec MX6021

As i understand U1 is NCP1351D https://cdn.badcaps-static.com/pdfs/...f4ba3fa041.pdf may be version D (Latch not connected on board)

[eccerr0r]

Re: Altec MX6021

Does the DBT bulb turn on and stay lit if the transistor isn't in the board?

If so - look into diode or main capacitor shorts.
if not, then suspect feedback, U1, transformer, or output.

If U1 fried, quite possibly it would fry the transistor again...

[Th3_uN1Qu3]

Re: Altec MX6021

If U1 fried, quite possibly it would fry the transistor again...

Indeed. When you have a switching mosfet short circuit, connected to a controller chip with low (under 100 ohm) or no gate resistance, it is recommended to replace both switching transistor and controller chip together. This is valid for all switching power supplies.

I once blew 2 sets of mosfets and 3 charge control chips in an Acer laptop which had a no battery charging fault. The final time i replaced both the mosfets and the charge control chip and everything worked fine then.

[naveenbedre]

Re: Altec MX6021

U1 1351D PATM can i replace with UC3842

[momaka]

Re: Altec MX6021

U1 1351D PATM can i replace with UC3842

No.
They have different pinout and made for different circuit.

[Agent24]

Re: Altec MX6021

Get the NCP1351D from UTSource, that's probably your best option for cheap. https://www.utsource.net/sch/NCP1351D

MOSFET blows up and takes out the controller, usually.

I'd suspect the glue caused the MOSFET failure. Remove all of it. Heating it with hot air makes it easier to get off.

[zerbino]

Re: Altec MX6021

Hello, guys.
I personally could not repair the breakdown, so I gave it to the service center. The specialist told me after the repair that he replaced the "some kind of diode" and it all worked. Although before this I replaced 1 transistor near C3, and 4 resistors 1Ohm and a capacitor. But I did not have enough the mind and knowledge to diagnose and understand that there is also a diode out of order. By the way, it was not necessary to replace U1. It was working, as well as the rest of the resistors.
Thanks to all.

[naveenbedre]

No.
They have different pinout and made for different circuit.

Thank you for reply

[zerbino]

Re: Altec MX6021

Bought NCP1351D at this place.

[naveenbedre]

No.
They have different pinout and made for different circuit.

Thanks

[ant3202]

Re: Altec MX6021

Ahhh finally someone has a decent pictures, seems this power board is failing.....

my infineon mosfet seems to be shorted, all beeps ....

[lincolnkorg]

Re: Altec MX6021

Has anyone had success in repairing the power supply? I am a hobbyist, got a unit from a friend to fix. Someone has already tried working on the board earlier.

So far from what I've tested, the fuse, rectifier diodes, mosfet, the 4 SMD resistors at the bottom, filter cap (bulged on the top) seems to be the problem. Do zener diodes need to be replaced? Does anyone have all the part numbers? What else could have failed along the way.

I also noticed that C25 was mounted in an angel, wondering if this was tampered by the previous person who tried to fix it. The polarity of C25 is reversed (smaller reading on diode test on one side and bigger reading when the probes are reversed, not sure if this is the right way to test) when compared to C24. Does that matter? Should I reverse C25 to match C24?

Any insights would be of great help.

I haven't tried to power the unit yet, the area around the fuse looks a little burnt.

Thanks in advance.

[Agent24]

Re: Altec MX6021

Can you post photos showing these parts especially C25?

You can't test capacitors in diode test mode except for a short so the results are meaningless.