How to test 1M0880 FPS?

[mikay786]

Hi guys need some help with this Loewe 525 Indvidual Subwwoofer which doesn't seem to be powering on.

AC is coming through, bridge rectifier is ok and outputting I think was 350v and main filter cap is reading 350v across it. A little further ahead there were a couple of blown 470k Resisters I think which are around 1w (Though not sure)

I replaced these resisters with 470k 0.6w !! which I thought would be ok just to test. I did buy 2w ones but lost them on the way home and they were the last two in store so had to go with 0.6w ones which again I thought would be ok to test until I get 2w ones.

Anyhow this hasn't made a difference, I'm not getting any voltages further down for example of the 2 big caps up top am not getting any DC voltage.

The blown resistors are connected to pin 3 VCC of the 1M0880 FPS so thinking it could possibly be the cause?



How do I test this?

[budm]

Re: How to test 1M0880 FPS?

When you said the two 470K resistors were blown, what do you mean by that? Open circuit? Are they really are 470K Ohms?
Did you check or replace the startup/running cap C911 in the primary side?

[mikay786]

Re: How to test 1M0880 FPS?

The 470k Resistors were covered in that glue stuff which was charred.

Measuring on multimeter the ohms reading just keeps climbing, currently at 17.92M Ohm and climbing. Is that open or short circuit? On transistor tester thing just says unknown / damaged part.

Colour band is Yellow, Violet, Yellow, Gold



I tested C911 capacitor which is a 50v 47uf cap and it tested ok.

Ive tested the diodes too and they seem fine in circuit.

[budm]

Re: How to test 1M0880 FPS?

OK, the glue damaged the resistors.
They look like 1/2W resistors MOX type.
The replacement resistors you put in do not look like they have the correct color code, they are 5-band and the colors do not look right to me.
It looks to have Yellow, Gray, Black, Orange, Brown.
Can you provide straight shot pictures of the top and the bottom side of the board without the red markings?

[mikay786]

Re: How to test 1M0880 FPS?

The guy at the store measured the resistors before handing them over.

The colours are, Yellow, Violet, Black, Orange, Brown. They are 0.6w and are significantly smaller that the old ones.

[budm]

Re: How to test 1M0880 FPS?

OK, the replacement are 1% resistors.
So did you check or replace C911?
BTW, all the rectifier diodes on the cold side tested OK?

[mikay786]

Re: How to test 1M0880 FPS?

Ive tested all the caps and they all measure good aside from one on the secondary side C933 which is slightly low (black small cap below 3 row transistors top right) 1000uf 10v measures 850uf.

Tested row of components where the burnt resistors were and all ok, ceramic caps, and diodes / resister.

[mikay786]

Re: How to test 1M0880 FPS?

Checked C911 and it measures ok, I can replace and try as I should have a suitable replacement?

I have not tested the diodes out of circuit, but in circuit they seem ok. I will though now.

[budm]

Re: How to test 1M0880 FPS?

So D925, 927, 931 are all OK?

[budm]

Re: How to test 1M0880 FPS?

BTW, what DCV are you getting on the VCC pin of the SMPS IC with the new resistors installed? Make sure to use Negative leg of the main filter cap as the GND ref. for the meter.

[mikay786]

Re: How to test 1M0880 FPS?

In circuit they appear fine, directional but I will pull them out now and try.

[mikay786]

Re: How to test 1M0880 FPS?

BTW, what DCV are you getting on the VCC pin of the SMPS IC with the new resistors installed? Make sure to use Negative leg of the main filter cap as the GND ref. for the meter.

Is that the IM0880?

Will do after I get these diodes out and tested. D925, 927, 931

[budm]

Re: How to test 1M0880 FPS?

Is that the IM0880?

Will do after I get these diodes out and tested. D925, 927, 931

Yes, IM0880.

[mikay786]

Re: How to test 1M0880 FPS?

Yea I was playing with it yesterday but didn't know how to measure it properly, I had the black lead going to pin 2 ground and red cable going to pin 3 vcc but readings were all over the place.

So I should use filter cap negative as ground.

[budm]

Re: How to test 1M0880 FPS?

BTW, there are 3 black devices with mounting hole and one with metal tab also with mounting hole, what are the P/N? The designators are IC921~924?
BTW, the top side pictures are not straight shots and not clear enough to read the designator for those 4 devices in question.

[mikay786]

Re: How to test 1M0880 FPS?

D925 and D927 rectifier diodes are ok reading 0.4v

D931 (SFAF1004G)

http://pdf1.alldatasheet.com/datashe...SFAF1004G.html

Which in diode mode is directional and reads 0.415v so good again I assume

[budm]

Re: How to test 1M0880 FPS?

BTW, the Vstart (Voltage at the VCC pin) for the IM is 15VDC.

[mikay786]

Re: How to test 1M0880 FPS?

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

IC921 (Metal tab) - KA7912

[mikay786]

Re: How to test 1M0880 FPS?

Ill get it put back together and measure the IM0880 VCC which should be 15VDC, with ground coming from negative on the filter cap.

[mikay786]

Re: How to test 1M0880 FPS?

Ohh yea before I forget there was some heavily burnt glue underneath the encapsulated resister top right near the two big caps. 470 ohms resister but it measured ok and so did the caps next to it.