Iraud 350 problems :(

JazmynFox

Member
2016-05-30 4:08 am
Hi everyone.

I just built my iraud350 amplifiers and I have run into a problem.

One of the amplifiers runs the 95v side at 110v. This makes the caps very unhappy :(. They draw lots of current and get very hot. I didn't notice it at first and one of them got so hot it popped. Poor cap.

Anyways I have lots of replacement caps so it's not a big deal.

Does anyone have a schematic on these amps or have any idea why it would do this?

One of the amps works perfectly with 55v on one side and 95v on the other.

I am running it from a 1000va toroid at 45-0-45v. It is over 100v even if I run the board at 25-0-25v using a variac.

Perhaps I just got a bum board :(

Any ideas?

Thanks
 

JazmynFox

Member
2016-05-30 4:08 am
Ok so heres an update.

Each side should be at 55v.

One of my amps run at 55v on both sides. However one runs at 55v and 110v.

When I remove the load they are both at 55v. :(

I am driving 16ohm electrostatic panels in parallel for 8ohms.

Seems they would be ok with 8 ohms but I know electrostatic speakers are weird loads.

Maybe this is a load problem? Either way... Can it be fixed?

Thanks
 
There is no lower frequency than DC, casually speaking.
DC at the output will definitley lead to bus pumping if the DC current is higher than the idle current from the opposite rail. The very low DC resistance of your step-up transformer doesn't help it either.
For a quick and dirty test I would put a large cap in series of the primary in order to see whether the bus pumping is gone and if you can play music.
If that is the case the cause of the DC offset has to be found. Maybe it is even within limits of that amp. In this case some DC trim has to be amended.

Regards

Charles
 
I calculated the size of the capacitor needed to achieve 20hz to be about 10,000uf.

That might be hard to find in a non polarized capacitor. :(.

Perhaps these speakers just aren't quite right for these amps. Although one amplifier handles it fine :/.

Would a 10,000uf 100v polarized capacitor work? I have a feeling the polarity could be a problem with AC. Many polarized electrolytics are very unhappy with AC.

I might just have to wait for the new module to get here. It's possible I just got a dud.

Another idea is finding a 1/1 output transformer and using that to block DC on the output.

Not really sure.

Thanks everyone.
 
You don't need to reproduce 20 Hz just to try if it works. I didn't mean to use a cap as the final solution. Just to try whether the problem is caused by the DC current and if the amp is working fien otherwise. I would fake a non polarised capacitor by using two electrolytics in anti-series for this purpose.
How large is the DC offset ? Maybe it is even withoin the usual limits of this amp. But with a DC load of 0.3 Ohms it doesn't take a very high offset voltage to cause bus runaway.

If the amp is not defective it might be a good idea to try some kind of offest correction.

An additional 1/1 transformer would block DC between its primary and secondary windings. But its primary winding would still see DC and this is what the class-d amp doesn't like. To be more exact: Class-D amps as such can handle DC current and very low frequencies just fine. It is the PSUs that have a problem with the current that the amp pumps back into the rails. It would of course be possible to build PSUs that can handle this properly.

Regards

Charles
 

JazmynFox

Member
2016-05-30 4:08 am
Hi,

I got the new board today and it has no problems. Works fine with no DC offset even on the 0.3ohm primaries of the Electrostatic step up transformer.

I am guessing the output transistors on the other board were poorly matched? I really don't know.

I have heard that you can replace the transistors with higher quality ones for better 2ohm performance.

Any ideas?

I have also thought about using iraud 200 boards instead. I have heard they are a bit nicer quality. I am looking for amps that can do about 500w - 1000w into 4ohms and 300-500w into 8ohms. Know any alternatives?

Thanks again.
 

ShopFloh

Member
2017-10-23 7:52 pm
You don't need to reproduce 20 Hz just to try if it works. I didn't mean to use a cap as the final solution. Just to try whether the problem is caused by the DC current and if the amp is working fien otherwise. I would fake a non polarised capacitor by using two electrolytics in anti-series for this purpose. ...

Charles

Hello dear community! Sorry for my English, I come complete with Google Translator, understand only German language. Here is my 1st post to you professionals: :)

I have received in Germany 2 plagiaries IRAUD350 via eBay from China.
These modules are equipped with Mosfet B23N20D and both modules were broken immediately within 3 weeks with silent music in the closed PA housing with good fans via flash.

Can I install the IRFB4227PbF 2x without further changes?

On the right was a semiconductor, I would like to buy it in Leipzig tomorrow. But what is the name of the part? The problem is, I find the IRAUD350 no exact circuit diagram in the Internet.

The manufacturer and the seller are probably not really reputable, I have on request no useful answer get.

Can you help me here please?