Rcf art 415a protected

[Amingpx]

HI
rcf art 415a protected.
The green and red lights are bright together. Gate pin in Mosfets ate not enabled through IRS20955s...There is 12 volts in irs . It's a problem with the IRS or ADAU1701?

[Amingpx]

Even I changed a new adau1701..unfortunately the problem didn't not ok

[x-pro]

what supply voltages are available?

[izzzzzz6]

Hi. I think i have this same issue on an RCF 715-A mk4
Voltage seems too high on amplifier mosfets gate and opposite output pin have around 3-4v on bad amp but opposite output pin on good amp mosfet has between 0.2v or 0.7v (might be a bad bias voltage?) on the opposite side of the gate, not sure why the voltage difference. thought it might be a shorted drive chip but i think they are ok. did you have any luck with the repair, i could do with a schematic and i might throw it on the scope later to look for a gate waveform. Thought it was power supply to begin with but that part seems ok. green led's on board are lit, all 3 led's on the rear panel are lit.
Just noticed that on the bad amp there is no 10V on IRS20955s pin 2 (CSD) but on good amp there is. also, small transistors next to these ic's read differently, on good amp roughly -2v and +2v and on bad amp they read only close to 2V on one side only.
Need schematic really, pin 2 of those ic's go to TP6 and TP7 (test points between these IC's) and to Q2 and Q3 a bit further back.
where i seem to be missing the 10V These IC's are the mosfet drivers, perhaps they could be damaged I'm not sure if the 10V is feeding into the IC or supposed to be coming out from the ic. Those pins are to do with the PWM i think the op amps drive some small transistors that then feed the IRS20955s. something along this path may be damaged.
Typical. I now lost part of the good amp, must have shorted something while checking voltages, i've now lost the 10V on one side of the good amp and gate voltage is replicating itself on the speaker output pin.
Not sure where to go now, i'll check the pwm on pin 3 PWM inputs and order some 20955s, for some reason the gate is driving the mosfet just enough to equal it's own voltage on the mosfet output.

The voltages i was quoting were measured from a ground same as speaker ground, however if you measure from the COM pin 9 to VDD and CSD it's a different story. the IC can be fed with up to 200V (between ~90v and ~100v in this case depending on your board). I'm taking another look at those voltages, on my last good side i get around 90V between COM and VDD and CSD shows a very tiny difference, on the side i just damaged it does not seem to be the same as the amp i was trying to repair, but it almost got as bad but the difference in the voltage between VDD and CSD on the most recent bad side has a bigger voltage difference.
If i use the same common as earlier (speaker -) i see about 1.6V on the latest damaged side on CSD but on the amp that came in for repair i'm seeing closer to 0v here. where it shows closer to the VDD voltage on the last remaining good side. These are pretty pricy at €8 each and i don't know if this is where the fault is, i might need 3 of these now or i may not need any, i guess i will order one for now to see if it fixes the issue on my amp that just became damaged.

This thing is like it's booby trapped. I removed the 2x IRS20955s and went to check voltages on the pads, after a min or so the power supply died and now it just whines, no power at the 2nd rectifier array. nothing or very low at the opto isolator.

https://pdf1.alldatasheet.com/datash...20955SPBF.html

[izzzzzz6]

Here is some more info on a very similar device, i used subtitles and then auto translate to try to follow along.
youtube video:
https://www.youtube.com/watch?v=3UVMQYsF2LQ
Irs20957s нюансы.

[x-pro]

Take a picture of your module from the printed side. A high quality one, please. This is important.

[izzzzzz6]

Hi x-pro. It is the same as the one pictured by the OP. What exactly do you want to see in the photo?

[izzzzzz6]

I could not find a service manual for the RCF 715 but i found a similar circuit on the mackie site. This uses a very similar IRS driver so it's almost the exact same layout. If i measure from the speaker negative as common the good amp had 10V on pin 2 of the IRS driver but the damaged board had lost this voltage. The gate voltage on the mosfet was being replicated on the output pin on the bad board.
On the good board i had around 4v gate voltage on one side of the mosfet and only around 0.2v on the opposite pin.

[x-pro]

Hi x-pro. It is the same as the one pictured by the OP. What exactly do you want to see in the photo?

I know what all RCF art series modules look like.
I am interested in the presence of silicone or glue on the board.

[izzzzzz6]

Right. On the module i was trying to fix it is pretty clean. That one is a Mk4 it looks like they stopped the glue from dripping through the holes to the tracked side of the board the open through holes seem to have been plugged before the glue was applied.
However on one of my personal modules it is a little older perhaps Mk2 (it looks identical) but there is brown glue that has made it to the under side of the board. This module was working 100% but while i was probing around taking voltages to make comparisons i must have damaged something as now i have a similar problem on my module one side has lost the voltage on pin 2 at least it is much too low compared to before, not as low as on the 1st module i was trying to repair but i think it was 1.6V when before pin 2 had around 10V.
So far it seems that either i have damaged the IRS IC or some of the network of transistors diodes and resistors that balance everything out on either side of the IRS IC.
I have ordered one of the more expensive IC's from ali ex. I will go through all of the transistors ect. in that zone then i will refit the ic and see if i get my voltage back. If this works i will try the same with the 1st module.
The problem with the 1st module is that it did not like having the IRS chips removed. After a few mins the psu died.
First i will replace the IRS chipset then i will start to problem solve the power supply, perhaps there is a protection that kicked in but i don't think so because it took a few mins to die on me.

[x-pro]

Clean off all the brown glue until the board is clean.
Then check all the transition holes.
The probability of the IRS20957 malfunctioning is small, if the output transistors are functioning properly.

[izzzzzz6]

There is no glue on track side of the mk4. Only on my amp (a Mk 2) which was fully working till i started probing it for comparisons. There is between 70V and 100V across IRS if you measure from the common pin 8 to VDD pin 1 so if you short pin 1 to pin 2 by mistake! Anyway. I will clean off as much glue as i can from my amp but i have not put any time into it for a few days. I have been repairing some crappy behringer speaker for a climbing gym and doing some other projects of my own. I will have another look soon. Either way i will post any progress here eventually, if i manage to make any progress.
Thanks for the advice.

[izzzzzz6]

I removed the glue and went over a few things and it appears my amp has come back to life, at least the voltage on that pin went back to normal. I'll soon get around to fitting the irs ic's back on, at least, i have one new one for now to try.

[izzzzzz6]

Still looking at the RCF-715A I put both IRS chips back and replaced all 4x IRFB4229 the problem is the same as before. Red protect light is on as well as normal power up led sequence.
Seems like one IRS chip is not firing correctly.

Could this be a capacitor near the IRS chip? Could it be a power supply problem?

x-pro mentioned glue but on the mk4 there is no glue on the underside. I assume that this semi conductive glue causes gates to fail on the tiny transistors near to the IRS chip.

This leaves me wondering if glue on the component side could be causing the irs chip (or small transistors close to it) to fail, stopping it switch on correctly, breaking down or going into some sort of latching feedback loop. Removing components and glue from the component side could be tricky. Perhaps the glue is shorting a capacitor. I need to spend some more time looking and perhaps with the scope to compare against a good amp. Did anyone find a more precise solution?

[x-pro]

When the module is plugged in, what is the 3-LED indication? How many times does the red LED blink?
The amplifier power supply should be +80V, -80V, +9 or 10V,- 9 or 8V, +12V relative to minus 80V and the PIC16xxxx, 24LC124(256), ADAU1701 power supply should be +3.3V