245BW, can't find problem. No 24 or 6.3V, standby is good.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

I'm doing a shopping list. What else possibly could blown? I'm ordering some parts from Farnell so I can get everything in one go. I'll get the zeners, 100ohm smd resistor (RT852), mains caps, 22nF cap, 0.22ohm resistor. What else?

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

I checked CX801S, CX802S and CP802S (circled). I only have multimeter with capacitance test. I read CX801S - 312nf, CX802S - 315nF and CP802S - 480nF. That look fine to me.

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Hmmmm.....

Could you have a bad mains cap?

T

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

That was stupid what I've just done. I replaced blue cap with 100nF mkp and power resistor with 1.5R 5W one and powerd up. Resistor blow up loudly and two QM802 and QM802 are dead.

I go to sleep...

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

I will order and replace all four BZX84C22 and two LMBD2838LT1G.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

I lifted the jumper. Still cant see 24V.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

<<Oh yes RT852 shows 168R>> ??
What does that mean? Its marking or the value you read with a meter?




Tough to say. Don't know what its original value was.


T

Sorry I mean read value is 168R
Oryginal value of RM801 is 0.22R 1W.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

I powered it uup with this large resistor I had. Unfortunately nothing changed.
I checked voltage on this large blue cap. Should it fluctuate from 300V to 330V-ish? Up and down all the time.
Same unstable voltage on QM802 as per pic attached.

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Good shot. I didn't find it because it is not in caps category. Thanks.
Hopefully I won't need it and the new RT852 will sort it out.

No. The problem is likely in the Zener's and possibly QT851. Lift that 24v jumper and see if 24v comes back.


<<Oh yes RT852 shows 168R>> ??
What does that mean? Its marking or the value you read with a meter?

Closest value I've at home is 1.4R 5W. Do you think it would be ok just for tests?

Tough to say. Don't know what its original value was.

@Toasty If he needed to replace the Long Blue cap could he use one of these?
http://www.ebay.co.uk/itm/PANASONIC-...=e100084.m1843

Yes, that should be fine.

T

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Good shot. I didn't find it because it is not in caps category. Thanks.
Hopefully I won't need it and the new RT852 will sort it out.

[selldoor]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

@Toasty If he needed to rplace the Long Blue cap could he use one of these?
http://www.ebay.co.uk/itm/PANASONIC-...=e100084.m1843

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Closest value I'got at home is 1.4R 5W. Do you think it would be ok just for tests?

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Oh yes, the power resistor is blown. That was the very first component I checked but I can swear it was good. Strange... ok I'll replace it and I'll report.
Oh yes RT852 shows 168R.

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

<<Both QM802/803 are brand new.>>

I know that. I'm saying check the power resistors right in front of them. Usually they go when one or the other FETs blow. Current limiters (fusible resistors).

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

RT852 looks blown. Same appearance as in my pic above. IIRC it's a 100Ω.

T

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

A picture you asked for

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Both QM802/803 are brand new.
I haven't got correct value to replace 12nF blue cap. Closest value I've got is Wima MKP 100nF 400V. This is almost impossible to buy in the UK. Only Farnel has it but minimum order of £20 apply :/
All SMD transistors and resistors in the section you mentioned seems to be ok. I will attach pic in few minutes.
One more I think important information. The input voltage on the large transformer is 0V.

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Check the long blue cap as in post #46.

Check the power resistors in the drains(?) of QM802/803. One mounted horizontal next to long blue cap and one vertical.

Make sure you are measuring from ground on the correct side for the 5.3v & 24v. Once you cross the fat white line and cuts in the board you are on a different circuit.

On the foil side, check the SMD components on the COLD side between the large transformer and the connector for the 5.3v standby. This would be near the optoisolators. (See attached pic.) I have found SMD resistors burned and a transistor there also. Use some good light and magnification to carefully inspect (jeweler's loupe).

A clear, well lit photo of that area would help.

If you follow the 24v circuit from above the transformer to the connector/area for the 5.3 & SB voltage, there is a wire jumper that you can lift one side of and see if the 24v comes up. ( J830 ? ) If it does, the fault is in the section near the opto's, as I mentioned.

There is a "balance" circuit used here that looks at the 24v & 5.3v. (2 zener's and a dual diode) If either one goes too far out of spec (high or low) it causes one of the opto's to send a signal to the shutdown pin on IC801S.

T

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

No, only 35mV. But when I keep the probes on it's going slowly up to about 47mV.

[selldoor]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

So - if you unplug the inverter board does the 24v come up on the power supply?