I have a JL 500/1 that was gifted to me to fix. When I got it, Q505 was shorted on the output section, and Q600-607 was burnt to a crisp, the same as R600-607. I replaced the power section fets and gate resistors. Its working power section seems to work. I have D600(rectifier) removed. I have the fets in the output section removed. I have the drain/source of Q505 and Q506 jumpered. I suspected U500 was the gate driver; however, there was no change after replacing it. I am not injecting a signal.
Attached are the gate drives. It's a single trigger for applying power/remote simultaneously. CH1 is the input power, and CH2 is the gate drive. If a look at 40uS would be useful, I can grab that.
It looks like the PWM is trying to come up, and then something latches it. I am not sure. I am not an amplifier expert, and I have only seen the inside of JL once before this. I might be overlooking something simple to you guys.
Can y'all look at these gate drives and give me an idea of where to look next? Does anyone have a schematic?
Attached are the gate drives. It's a single trigger for applying power/remote simultaneously. CH1 is the input power, and CH2 is the gate drive. If a look at 40uS would be useful, I can grab that.
It looks like the PWM is trying to come up, and then something latches it. I am not sure. I am not an amplifier expert, and I have only seen the inside of JL once before this. I might be overlooking something simple to you guys.
Can y'all look at these gate drives and give me an idea of where to look next? Does anyone have a schematic?
Power B+ constantly and pulse the remote. After the pulse (and release), you have 15 seconds to view the gate drive.
The timebase will need to be at about 5us, not ms.
U500 is the gate driver.
Do you have the my tutorial?
The timebase will need to be at about 5us, not ms.
U500 is the gate driver.
Do you have the my tutorial?
Yes, I wasn't in the uS at the moment because I was trying to show the behavior. By the way, the stand-by current is 27ma before the remote pulse and 105ma for about 15 seconds at 12V.
If I do what you describe, I get the same results: a little bit of pulsing for 100ms and then stuck high or low, as shown above. Here is the Q505 Gate at 10uS so you can see what it's doing while it does work in the 100ms window.
I don't have the paid version I did read the demo back in 2019 during my first dive into amplifiers. Im so glad to see you are still at it! give me a minute to get back into my paypal and I will order it now.
If I do what you describe, I get the same results: a little bit of pulsing for 100ms and then stuck high or low, as shown above. Here is the Q505 Gate at 10uS so you can see what it's doing while it does work in the 100ms window.
I don't have the paid version I did read the demo back in 2019 during my first dive into amplifiers. Im so glad to see you are still at it! give me a minute to get back into my paypal and I will order it now.
With or without U513 having pin 1/2 bridged? I assume I need to solder some flying leads on and put the preamp back on to look at it.
CH1 is pin 4 CH2 is pin 5.
Edit: so is the duty cycle set on this comparator? rising and lowering the voltage on pin 4?
Edit: so is the duty cycle set on this comparator? rising and lowering the voltage on pin 4?
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That op-amp appears to be defective. With pins 1 and 2 bridged, they should follow pin 3. I doubt that anything is pulling the voltage of that output high since there is a series resistor feeding the circuit it drives.
Yes that makes sense. I will get a new OPA 2134 on its way here. I will report back in a few days when the part gets here, but looking at the datasheet and board, that makes sense.
Thank you, Perry!
Thank you, Perry!
Has that op-amp been replaced? I have it as an NJM2068. For testing, it's not critical if you want to drop something else in until you get a replacement.
Looking at the solder job it's looks right from wave solder or other automated process. It doesn't look to have been replaced. It's a JRC 2134B. Unfortunately I haven't done amplifiers since at least 2019 and looking through my old project bags I'm not seeing any dual channel op amps other than some THT stuff.
Are any of the op amps in the preamp section non critical? Looks like there a number of the 2134 up there.
Are any of the op amps in the preamp section non critical? Looks like there a number of the 2134 up there.
I found an OPA 2172 tucked away, so I tried it even though it's just a GP. It acts the about same.
I get 1.2V on 1/2 and 2MV on pin 3.
I removed the bridge solder bridge and pin 1 is 2.3V and pin 2 is 281mv
It looks like something downstream of pin 1 is the problem. where else does it go other than the comparator through the 2 1K resistors?
I get 1.2V on 1/2 and 2MV on pin 3.
I removed the bridge solder bridge and pin 1 is 2.3V and pin 2 is 281mv
It looks like something downstream of pin 1 is the problem. where else does it go other than the comparator through the 2 1K resistors?
What's the DC voltage on the power supply terminals of that op-amp?
I don't think that the op-amp's output could be driven that way through the 1k resistor that it has on its outputs.
I think there may be LEDs connected to the output of that op-amp.
I don't think that the op-amp's output could be driven that way through the 1k resistor that it has on its outputs.
I think there may be LEDs connected to the output of that op-amp.