How to test 1M0880 FPS?

[budm]

Re: How to test 1M0880 FPS?

IC922 (LEFT) - KIA78R12PI
IC924 (MIDDLE) - KIA378R05PI
IC923 (RIGHT) - KIA78R33PI

IC921 (Metal tab) - KA7912

Thanks, they are Voltage regulators ICs.

[mikay786]

Re: How to test 1M0880 FPS?

alright it seems to be fluctuating between 11v upto 14v jumping around within that range, not constant. Measured from filter cap negative and 3rd pin vcc

when I turn the power off and measure at same place once its below like 10v it declines in an orderly fashion not jumping up and down.

Main filter caps has 347v

Measured the large two caps top right again which are 2200uf 50v and they have nothing going through them just mv

[budm]

Re: How to test 1M0880 FPS?

So it can be bad startup cap C911 which is connected to the VCC pin, or the circuit detects problem so it is in the startup-shutdown mode, or bad SMPS IC.

[mikay786]

Re: How to test 1M0880 FPS?

I replaced that cap with a Panasonic FC or FM of same value

[mikay786]

Re: How to test 1M0880 FPS?

Could the resistors I replaced being of too small wattage cause this error?

Thinking I should wait and replace with the correct size ones before proceeding

[budm]

Re: How to test 1M0880 FPS?

Please check the resistance between the two legs of C921, C928, C932, C924.

[mikay786]

Re: How to test 1M0880 FPS?

C921 - 4.8m ohm or 18k ohm keeps changing everytime I go back and measure!
C924 - 18.5m ohm
C928 - keeps droping. started off at 8m ohm now 4.2m ohm and falling slowly
C932 - 0.44k ohm

[budm]

Re: How to test 1M0880 FPS?

C921 - 4.8m ohm or 18k ohm keeps changing everytime I go back and measure!
C924 - 18.5m ohm
C928 - keeps droping. started off at 8m ohm now 4.2m ohm and falling slowly
C932 - 0.44k ohm

OK, they are OK, no very low resistance reading, so more likely the problem is in the power transformer drive circuit.
Since the startup cap is already changed, next thing will be the SMPS IC itself.

[mikay786]

Re: How to test 1M0880 FPS?

http://www.ebay.co.uk/itm/1M0880-KA1...sAAOSwv0tVcz8Y

is that the correct part?

[budm]

Re: How to test 1M0880 FPS?

http://www.ebay.co.uk/itm/1M0880-KA1...sAAOSwv0tVcz8Y

is that the correct part?

That is the one.

[mikay786]

Re: How to test 1M0880 FPS?

Alright ill get that ordered, seems to be a discontinued part so will have to order one from eBay rather than pick up from farnel.

How come its not blowing fuses? normally when a part is bad something blows

[budm]

Re: How to test 1M0880 FPS?

It will blow the fuse if the internal power MOSFET is shorted out (PIN 1 to pin 2).
The VCC pin has internal 32V Zener for protection, it can be bad.

[mikay786]

Re: How to test 1M0880 FPS?

Alright so when I replace and measure pin 3 we should be getting a constant 15vdc on that pin?

[budm]

Re: How to test 1M0880 FPS?

Alright so when I replace and measure pin 3 we should be getting a constant 15vdc on that pin?

The VCC should rise up to 15VDC then the IC will start driving the transformer which at that point the AC from AUX winding of the transformer is fed to fusible resistor R913, the output side of R913 (verify that it is OK, it is probably low Ohms resistor between 1~10 Ohms range) feeds the rectifier by D911 and filtered by C911 to supply the steady DC to run the IC, probably around 18~20Vdc range (Max VCC is 30V).

[budm]

Re: How to test 1M0880 FPS?

BTW, I am curious as the resistance between the VCC and the GND pin is.

[mikay786]

Re: How to test 1M0880 FPS?

in circuit?

pin 2-3 resistance is fluctuating in the m ohms

0.4m ohms but jumping about

[mikay786]

Re: How to test 1M0880 FPS?

R913 resister was good, measured it earlier and in spec

33 ohms

[mikay786]

Re: How to test 1M0880 FPS?

Changed the 1m0880 with same results. so looks like it isn't the issue.

[budm]

Re: How to test 1M0880 FPS?

So the VCC on the 1M0880 is still low and fluctuating?

[mikay786]

Re: How to test 1M0880 FPS?

from 10v to 14v

That could be just not being able to get prongs on consistent causing fluctuations