Dead Channel Issue with SURE IRS2092

neyurt

Member
2016-03-17 10:40 pm
I have bought a few SURE IRS2092 Stereo modules from their site. The 2 x 125W @ 8 ohms version.

I use them with abletec +/-53v 450W power supply.

So both modules has the issue where upon powering up, 1 channel is dead (blue LED off) while the other 1 is on. However the dead channel would turn on IF I TURN ON THE PRE-AMP LOUD ENOUGH (around -10dB level). And it'll remain on till till I power cycle the setup and once it's up, lowering the input volume DOES NOT shut off the LED. I can only assume that this exercise of "jump-starting" the dead channel is required every time. Their spec sheet indicates that the blue LED indicates PWM oscillator is presence.

Although it is working after having to "jump-start" the dead channel on with high volume input, it gets pretty annoying to have to do that every time.

Since this happen on 3 different modules, is this some sort of limitation by the IRS2092 chip? OR I'm that unlucky to get 3 defective modules on the same shipment?
 

bullittstang

Member
Paid Member
2013-05-09 2:14 pm
Ft. Worth, TX
I will give you a few suggestions to try.
1) *That SURE board has under-voltage protection, at 55V, so that board may be extra sensitive. Have you used DMM to see exactly waht voltage you are getting to the board?
2) Do you have a load on the V3/V4 on that SMPS? The SMPS needs a resistor or load on those supplies or it can result in some weird things happening.
3) Have all 3 modules been the same Sure, 125w boards? or has this happened with different boards?
4) If 3 is YES, then you might look on eBay for some IRS2092 boards without the under-voltage protection. I currently use the same setup you have, but with (2)LJM L25D IRS2092 boards (they are mono channel boards) and it works great.

*read the spec sheet closer and UV is at 39V, so that shouldn't be the issue.
 
*read the spec sheet closer and UV is at 39V, so that shouldn't be the issue.

Where do you see 39V?

I see conflicting info on this page...

Sure Electronics' webstore 2 x 125 Watt Class D Audio Amplifier Board - IRS2092

The manuals say 55V...

http://sure-electronics.net/Sure Electronics Audio Amplifier Product Manual.pdf
http://m5.img.dxcdn.com/CDDriver/CD/sku.204110.pdf

So it's either 45V or 55V.

Could be an oscillating frequency problem. They don't say anywhere, but are the trimmers for output offset trim or to adjust the frequency?

EDIT: Ok, so the trimmers are to adjust the oscillating frequency (the board is exactly the same as IRAUAMP7S). You might need to adjust these to different frequencies for each board. So if you were running three boards together you could do 375kHz/400kHz/425kHz. You obviously need a scope or frequency counter to do this.
 
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neyurt

Member
2016-03-17 10:40 pm
Thanks for the quick reply guys. All 3 modules are SURE Stereo 2x125W IRS2092 boards.

I do have two 150 ohm 5W resistor connected to V3 and V4.

So I'm not even running 3 boards at once right now. And I plan to connect 1 Abltec 53+/- PS to each 2x125W module individually. So adjusting the freq for each board to differ wouldn't address this particular issue.

The key thing I see here is the fact that the dead channel can come alive IF enough input comes through. Can anyone characterize this condition??

And yes, it seems that the sure 2x125W is almost the same as IRAUAMP7S reference design. And I don't think this is an UV protection issue.
 
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So I'm not even running 3 boards at once right now. And I plan to connect 1 Abltec 53+/- PS to each 2x125W module individually. So adjusting the freq for each board to differ wouldn't address this particular issue.

The switching frequency for each channel either needs to be EXACTLY the same or at least 25kHz apart. This would be easy enough to try if you had a way to measure it.
 

neyurt

Member
2016-03-17 10:40 pm
Unfortunately I don't have the equipment to probe the switching freq.

I just assume that as a product, it would ship in a working condition without having to adjust the switching frequency. It's just also strange that all 3 have the same issues.

Sent from my Nexus 6P using Tapatalk
 

bullittstang

Member
Paid Member
2013-05-09 2:14 pm
Ft. Worth, TX

neyurt

Member
2016-03-17 10:40 pm
uploadfromtaptalk1460675670191.jpg

Actually I do have one on my phone.

But in here, both LED are lid up so this is after already "jump starting" the dead channel to turn it on.


Pretty simple setup. Just abletec PS --> amp module --> speakers
 
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bullittstang

Member
Paid Member
2013-05-09 2:14 pm
Ft. Worth, TX
If it is always the same channel that has issue starting up. I would try flipping the RCA's and see if the problem follows the RCA or stays on the same channel.
If it stays on the same channel, then try Rob's suggestion on that hard-starting channel.

EDIT - does it do the same with a "hotter" pre-amp, like an iPhone?
 
Rob, since this is a stereo module. Which output exactly do I need to try this?

And does it matter that only 1 side of the module starts up normally and the other doesn't?

Thanks!

Add the resistor for the channel that is not working properly.

Yes, if one channel works and one not, that's a sign that something is wrong with the design or they mounted the wrong component.
 

neyurt

Member
2016-03-17 10:40 pm
So according to the language by the reference design http://www.irf.com/technical-info/refdesigns/iraudamp7s.pdf

"With an oscilloscope, monitor switching waveform at test points VS1 & VS2 Adjust P1A &
P1B to change self oscillating frequency to 400kHz ± 25kHz.
Note: To change self-oscillating switching frequency, Adjust the potentiometer
resistances of P11A and P11B for CH1 and CH2 respectively. "


Here's the sure spec sheet:
http://www.parts-express.com/pedocs/specs/320-313s.pdf


Assuming I can find VS1 , using a multimeter in AC probe mode, I can point + to VS1 and - to any GND? Will I be able to monitor switching freq this way? I hear it's this board can be sensitive to probing so I don't want to accidentally blow it up! Any idea where this VS1/2 point might be on the board?

Im just hoping that changing the pot resistor to tune the switching frequency to 400hz will resolve this issue.
 

bullittstang

Member
Paid Member
2013-05-09 2:14 pm
Ft. Worth, TX
That is what I linked you to at Parts Express forum, assuming the 125w and 250w boards are labelled the same.
Turn the board over and look for R11B and R11A, which are the trim pots. There is a pic in the forum thread I linked.
According to their advice, adjusting these pots to 265-ohms, you will have adjusted your oscillation to ~400khz, or very close to it.