This amp came in with blown PS and outputs. Insulated STP60NF06FP in the PS. Gate resistors are 68 ohm 0603. Pulldowns are 4.7k. Drivers are MLZ transistors from a TL494.
Was wondering if IRFIZ48GPBF would be suitable to STP60NF06FP since those are not in stock anywhere. Need the be encased. Has anyone tried these or other combination? I also need to replace the 68 ohm gate resistors. Maybe go to about 33 ohm?
Outputs are IRFP250N pairs on each side, one of them blown on each side.
I clipped all bad parts and put two IRFZ44 temporarily in place in the PS. Amp is working.
Was wondering if IRFIZ48GPBF would be suitable to STP60NF06FP since those are not in stock anywhere. Need the be encased. Has anyone tried these or other combination? I also need to replace the 68 ohm gate resistors. Maybe go to about 33 ohm?
Outputs are IRFP250N pairs on each side, one of them blown on each side.
I clipped all bad parts and put two IRFZ44 temporarily in place in the PS. Amp is working.
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I rebuilt the PS with IRFIZ48GPBF and new gate resistors. Also replaced all 4x output transistors with brand new IRFP250N and put the amp back into the sync.
Now under load, the amp will only get to about half output (40A draw from bench, about 35vAC across speaker terminals), before acting up. The bottom waveform gets very distorted after that and the amp struggles to output anything higher.
Problem seems to get way worse at 2ohm load vs 4 ohm load where the amp will falter and output a similar screenshot but at 18A draw instead of 40A @ 4 ohms. Rail voltage is +-87vDC the whole time and the amp is not starving for bench power which is staying above 13.5vDC the whole time.
Any clues? Service manual?
Scope set to 20v/div. Inputting about a 75hz sine wave.
Now under load, the amp will only get to about half output (40A draw from bench, about 35vAC across speaker terminals), before acting up. The bottom waveform gets very distorted after that and the amp struggles to output anything higher.
Problem seems to get way worse at 2ohm load vs 4 ohm load where the amp will falter and output a similar screenshot but at 18A draw instead of 40A @ 4 ohms. Rail voltage is +-87vDC the whole time and the amp is not starving for bench power which is staying above 13.5vDC the whole time.
Any clues? Service manual?
Scope set to 20v/div. Inputting about a 75hz sine wave.
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Maybe the over-current circuit? Maybe something wrong with the low-side FETs/drive.
The last page of the attached service manual has a nice diagram. It may be the same as yours.
The last page of the attached service manual has a nice diagram. It may be the same as yours.
Its worth noting that with NO load, the output is absolutely fine looking out to clipping.
I reviewed the 9105D SM. It would definitely need translation on my part. I tried removing Q40 which is in the over-current section but that didn't help. Also not totally sure if I located Q40 on this amp by translation. I tried pulling three different transistors actually.
I reviewed the 9105D SM. It would definitely need translation on my part. I tried removing Q40 which is in the over-current section but that didn't help. Also not totally sure if I located Q40 on this amp by translation. I tried pulling three different transistors actually.
On the schematic, Q40 is a 2sa1163: https://www.mouser.com/datasheet/2/408/2SA1163_datasheet_en_20140301-1916313.pdf
CG on the top. My 9106D has only 3 of these transistors on the board.
Q371/Q372 on this amp are CG, connected to output fets, and actually have 10k resistors on legs as well. These are also extremely close to the speaker terminals. Pulling both did not help.
Q402 is the 3rd CG. Not connected to the output FETs and may be for something else entirely. No change removing.
CG on the top. My 9106D has only 3 of these transistors on the board.
Q371/Q372 on this amp are CG, connected to output fets, and actually have 10k resistors on legs as well. These are also extremely close to the speaker terminals. Pulling both did not help.
Q402 is the 3rd CG. Not connected to the output FETs and may be for something else entirely. No change removing.
What about Q49.
The over-current circuit has a positive and a negative half. They are sensing across the shunt resistors.
The over-current circuit has a positive and a negative half. They are sensing across the shunt resistors.
Hmm. Im going to try and locate the 9106D SM. I am not able to translate what Q49 is on this pcb.
Looks like I was right about Q371/Q372. I had already tried at the amp with those two removed and didn't help. I'm going to pop off Q376 next.
Found something interesting. If I put my scope probe set to 1X on the base or collector of Q304/Q306 OR Q303, the amp will pull out to 90A at 2-ohm clean. My probe is loading the circuit slightly. Also looks like the drive signal off of IC241 pin 3 and 11 is OK, but the signal on the base of Q304/Q306 and Q303 is rounded. Photo.
Q304/Q306 & Q303 are measuring OK in circuit. I'm actually wondering if reducing the 4.7k resistors at R301 and R302 may help? Seems drive may be weak here for some reason.
Or it could be IC241 is going? Is that even an audio device?
Q304/Q306 & Q303 are measuring OK in circuit. I'm actually wondering if reducing the 4.7k resistors at R301 and R302 may help? Seems drive may be weak here for some reason.
Or it could be IC241 is going? Is that even an audio device?
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I've seen a lot of transistors that looked OK on a meter but their high-frequency performance was not good enough.
Do any of the transistors in that area appear to have run hot?
In my opinion, the circuit is likely fine (no redesign needed, Japanese, not chinese) but without seeing multiple of these, it's hard to be definitive.
There are a lot of high-speed logic ICs being used in class D amps. At that point in the circuit, it's not audio.
Do any of the transistors in that area appear to have run hot?
In my opinion, the circuit is likely fine (no redesign needed, Japanese, not chinese) but without seeing multiple of these, it's hard to be definitive.
There are a lot of high-speed logic ICs being used in class D amps. At that point in the circuit, it's not audio.