SPMS repair, IR21531, please help.

[Rockstar Okan]

Hi guys;

My friend give me his mark bass amp. I checked, 220v fuse and mosfets are blown.

i changed mosfets with irfp460, and power on the amp. fuse blowned again.

There is a driver ic, but numbers on it erased by manifacturer.

Can i use ir21531? Or what is your choice? Please help me.

Schematic attached. Thank you.

[Enzo]

Thank you for drawing it out, but what model Markbass? We may well have the schematic already and it may specify the part.

[Jazz P Bass]

http://music-electronics-forum.com/t28280/

This post was on the Little Mark.

In that particular model, the IR21531DPBF worked fine.

Note: edit IC #

[Rockstar Okan]

Thank you.

Amp is Mark Bass Little Mark 250.

I read other thread, but they are different amps.

[MarkusBass]

Amp is Mark Bass Little Mark 250.
I read other thread, but they are different amps.

It is not important whether the amps are different, or not. It is important whether they have similar power supply, or completely different. In this case it seems that they are similar, or even the same. In the other thread it is clearly explained that IRF5131DPDF will work. What is important is that the IC is with bootstrap diode built-in. And IRF5131DPDF has the diode.

Mark

[diydidi]

Hi Guys.
I can't seem to source the IR21531D around here in South Africa only the IR21531. I was thinking, can't the diode be added externally?

[Jazz P Bass]

Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.

Pick a country that is close.

[MarkusBass]

You can always order it from China: Ir21531d-Ir21531d Manufacturers, Suppliers and Exporters on Alibaba.com

Mark

[Rockstar Okan]

I found IR21531D but i didn't fix it yet.



This is my schematic. I renewed mosfets and power on circuit after cut the red lines. No fuse blowing. Everything looks fine but when i measure A,B and C test points, readings are huge.

I measured between ground and this points.
A: 249V AC
B: 247V AC
C: -9V AC (when my multimeter set to 750V AC)
-126.7 V AC (when my multimeter set to 200V AC)

I don't have a Fluke, but mine is good, too.

Are these readings interesting? Too high? There are 63V caps, if i connect red lines, they can be blow up.

What's going wrong? Is this transformer failure?

Thanks.

[The Dude]

I'm thinking you have a grounding issue or your choice of where to reference ground with your meter is not correct/not working. In your measurement of TP C you say that the reading is different depending on what range your meter is set to. Meter range should have no bearing on voltage measured. Check that the transformer CT is grounded and use the same ground for your meter. You may also want to check continuity from outside windings to center tap of the transformer secondary. Possibly the CT opened up. Also note this is a switching supply. Your meter may not be able to properly read the AC frequency of the supply coupled with the fact that many SMPS supplies don't like to run unloaded.

[MarkusBass]

I don't have a Fluke, but mine is good, too.
Are these readings interesting? Too high? There are 63V caps, if i connect red lines, they can be blow up.
What's going wrong? Is this transformer failure?

I think that you are making two mistakes:
- an average multimeter is not capable of measuring AC voltages at this frequency (about 100kHz),
- most of switch mode power supplies do not work correctly without a load. And you even disconnected diodes and capacitors on the output.
You can check your multimeter with some signal generator.
If you are afraid that the caps may blow, put some resistors instead of the tracks that you cut. Check that the diodes are not shorted and then measure the DC voltage on the output caps. If you are still afraid to do it, send the amp to a service centre.

EDIT: another possibility of making a mistake is that you use the ground on the primary side of the transformer but this is not the same ground as on the secondary side. And you are just measuring mains supply voltage which has nothing to do with the voltages from the power supply. Check if this is the case.

Mark