200v 220uF Main Cap Replacement Advice?

[mikay786]

Need to replace a blown main caps on the PSU board on the Focal subwoofer I'm working on.

MHC 200v 220UF (CD293 85c) 22mm x 30mm (10mm Lead Spacing)

http://uk.farnell.com/panasonic-elec...rad/dp/1673462

http://uk.farnell.com/panasonic-elec...-in/dp/2357418

Not replaced main caps before but assuming just like any other. Not sure if I need snap in type like the second link or if the first link with 7.5mm spacing will do. That seems to be better rated @ 105c?

Or any other suggestions?

[ReeceyBurger123]

Re: 200v 220uF Main Cap Replacement Advice?

Either will work buddy

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

ordered the first one as diameter and ratings are better. Hopefully it works.

[ReeceyBurger123]

Re: 200v 220uF Main Cap Replacement Advice?

Hopefully let us know

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

No luck, still blowing fuses.

Just testing stuff around the entry point and have a varistor 14n471k and a thermistor SCK104.

The thermistor SCK104 is beeping on continuity test, is this normal or is it shorted? But is reading 14ohm at room temperature and does drop when heated.

the mov, I have no idea how to test, just doing some googling.

[diif]

Re: 200v 220uF Main Cap Replacement Advice?

Bridge rectifier ok ?

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Yep bridge rectifier testing ok

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Think ive found the problem. 4 x Mur 420 1014 Rectifier Diodes

one of them doesn't read in either direction in diode mode and is shorted.

Should I change all 4 or just the shorted one?

[budm]

Re: 200v 220uF Main Cap Replacement Advice?

Replace all 4 at the same time. It tested bad off the board too, right?

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Yes removed all 4 and tested. They seems to be in parallel?

Is one rectifying diode shorted enough to cause fuse to blow?

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Minimum order quantity was 5 so ill have enough to replace all 4

[eccerr0r]

Re: 200v 220uF Main Cap Replacement Advice?

I'd look for other devices downstream that could be bad like a shorted switching transistor before testing...

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

I'd look for other devices downstream that could be bad like a shorted switching transistor before testing...

You were right, shorted irf730 mosfet too.

Been a bad day, accidently ordered the wrong mosfet (mixed up a good ones with the bad one) so drove to farnells and bought the wrong one. Then checked online and it says they were open till 8pm so went back and they were closed!!

So far

blown main cap
Shorted diode rectifier
shorted mosfet

Quite a few bad parts but hopefully that's the end of it!

[momaka]

Re: 200v 220uF Main Cap Replacement Advice?

No luck, still blowing fuses.

This should help with that:
https://www.badcaps.net/forum/showpo...4&postcount=70

The thermistor SCK104 is beeping on continuity test, is this normal or is it shorted? But is reading 14ohm at room temperature and does drop when heated.

I haven't looked at the datasheet for that, but it is likely okay. If it goes open or high resistance (as in, over 100 Ohms), then it's bad for sure.

the mov, I have no idea how to test, just doing some googling.

MOV should read open-circuit on all multimeter resistance scales. Shorted or low resistance is definitely bad.

You were right, shorted irf730 mosfet too.

In that case, you might also have a blown Source resistor. Usually, that is a low-resistance resistor (under 3 Ohms typically) and connected between ground and Source pin on MOSFET. If it is O/C, it's bad.

Once you replace the diodes, it might be worthwhile to apply power to the PSU without the MOSFET in the circuit. The PSU won't start, but at least you will see if anything else is shorted. And definitely keep using the light bulb trick I pointed to above, until the PSU actually starts working.

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

There are a couple of resister connected to the source pins of the mosfets (pair of irf730's)

But they are 22ohm, I'll check them though. Red, red, black, gold, brown

[momaka]

Re: 200v 220uF Main Cap Replacement Advice?

I think those connect to the Gates. Usually, TO-220 MOSFETs have their pins as Gate, Drain, Source, in that order. Seeing that the MOSFETs are facing the transformer, that means their Gates are the top pins.

Still, if any of those MOSFETs blew, then check those 22 Ohm gate resistors as well.

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Your right seems like the source pins connect to the doughter board which is packed with diodes and resisters, so will have to remove and check that too

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Reverce

[mikay786]

Re: 200v 220uF Main Cap Replacement Advice?

Alright so pulled out the daughter board and pin 2 & 5 are connected to the resister in line with the source pin on the mosfets.

They are both reading 394 Ohm (0.394k Ohm), but having a hard time figuring out the colour bands to see if the readings are correct w ith specification. Asume they are as both read the same.

Looks like, Brown, Black, Brown, Gold, Orange

But there is no orange as the fifth band or if I reverse no gold as the 2nd band?

[momaka]

Re: 200v 220uF Main Cap Replacement Advice?

From the reverse side picture, it looks like there are NO Source resistors. So I guess that is one less thing to worry about now.