Good day all,
I have a pair of Prime 1200.1D’s in for repair, the first one here had a blown power supply and 2 of 6 outputs shorted. Removed all the bad FETs and checked PS drive, looked good despite the burned look of the PNP drivers, but when loaded it was obvious the drivers were bad. Sloppy looking falling edge on the drive wave, so the PNP’s got replaced and it now builds good rail voltage.
The output section doesn’t seem to be doing anything, and I have a blue power LED with red flashing along with it (bicolor LED). This uses the IRS2092S self oscillating output IC, and this is my first experience with it. My question is: will the IC create drive for the output section right away, or does it need a kick to get it going? I tried feeding it an input signal, no change.
It’s possible the chip was damaged by the shorted outputs, but is there a way to confirm it’s bad before replacing it?
I have a pair of Prime 1200.1D’s in for repair, the first one here had a blown power supply and 2 of 6 outputs shorted. Removed all the bad FETs and checked PS drive, looked good despite the burned look of the PNP drivers, but when loaded it was obvious the drivers were bad. Sloppy looking falling edge on the drive wave, so the PNP’s got replaced and it now builds good rail voltage.
The output section doesn’t seem to be doing anything, and I have a blue power LED with red flashing along with it (bicolor LED). This uses the IRS2092S self oscillating output IC, and this is my first experience with it. My question is: will the IC create drive for the output section right away, or does it need a kick to get it going? I tried feeding it an input signal, no change.
It’s possible the chip was damaged by the shorted outputs, but is there a way to confirm it’s bad before replacing it?
Digested the datasheet on it, seems to be cycling in and out of overcurrent protection. Pin 5 of the IC rises and falls at a predictable rate, in step with the red LED illuminating. Not sure why OCP is being triggered with no outputs installed, need to do more poking around to see if it’s the high side or the low side triggering it.
The IC uses the dynamic VDS when the transistor is switched on to determine if the FET is passing too much current. Without the FETs, the IC thinks the current is virtually infinite.
It 'may' be possible to fool the low-side by shorting the low OCset to the Vref.
The ICs are typically damaged when the outputs fail, depending on how they fail.
It 'may' be possible to fool the low-side by shorting the low OCset to the Vref.
The ICs are typically damaged when the outputs fail, depending on how they fail.
It cycles the same way with the remaining 4 good FETs in circuit, but I agree it could just be a bad chip. I would have thought the driver transistors between the chip and the outputs would have failed though and protected the chip, in the same manner as it usually goes with the power supply, but the drivers all check good in this case.
The data sheet actually says to short OCSET to VCC to disable it, as the circuit stands right now VREF goes through a 0 ohm SMD resistor to OCSET. This should mean the sensed D-S voltage has to exceed VREF (5.3v) to trigger a low side OC situation. I think I’m gonna try removing that 0 ohm resistor and bridging OCSET to VCC and see if that allows it to boot up. If not it’s sensing a high side OC, and I’m not sure how to test for that.
The data sheet actually says to short OCSET to VCC to disable it, as the circuit stands right now VREF goes through a 0 ohm SMD resistor to OCSET. This should mean the sensed D-S voltage has to exceed VREF (5.3v) to trigger a low side OC situation. I think I’m gonna try removing that 0 ohm resistor and bridging OCSET to VCC and see if that allows it to boot up. If not it’s sensing a high side OC, and I’m not sure how to test for that.
Well that didn’t work, and I think the 2092S has died as a result. My order of new chips came in though so I soldered a new one in but that one does nothing at all so now I’m sorta stuck lol.
In my experience if the outputs had gone they often took the 2092 with them.
Its a cheap IC so worth changing anyway.
It needs feedback to work so no outputs will stop it working.
Yes, we already established that. It’s currently doing nothing after IC replacement and outputs installed.
It can get stuck in reset mode if it thinks there is a problem.
Is the reset pin going up and down ?
It has a protect mode for over current etc and if it thinks there is OC it keeps resetting itself.
Is the VCC voltage correct and stable ? I think it resets if that is wrong.
Is the reset pin going up and down ?
It has a protect mode for over current etc and if it thinks there is OC it keeps resetting itself.
Is the VCC voltage correct and stable ? I think it resets if that is wrong.
Doesn’t seem to have any Vaa, that might be a problem. Vss seems to be 5v, references from PS secondary ground.
Sorry, got them wrong way around.
Vaa is 5 volts and Vss is -5 volts.
If either missing 2092 wont start up.
Come on its been about 3 years since I worked on mine !
Vaa is 5 volts and Vss is -5 volts.
If either missing 2092 wont start up.
Come on its been about 3 years since I worked on mine !
Ok just checking, assuming there’s gonna be a 5v regulator somewhere so I’ll see if I can locate that and determine why the voltage is missing.
Not sure how, but the chip was bad. Vaa was shorted to pin 2 (ground) internally. Not sure if I caused it or if it went bad on power application, but this is why I always order IC’s in pairs. Gonna look for shorts in the drivers on the output side real fast, then solder another one in and try again.
Now Vaa is being dragged down to .7v at pin 1 of the chip, while on the other side of the resistor feeding it I have a solid 5v. But the chip isn’t shorted this time, so I have no idea what’s going on this time.
Have you studied (not skimmed) the datasheet for this IC?
What about the iraudamp5, 7 and 9 reference design PDFs?
What about the iraudamp5, 7 and 9 reference design PDFs?