Hello, good morning, someone has repaired one of these amplifiers, it turns off that when I turn up the volume it goes off, someone has an idea where I should start, I know I have a long way to go and learn to read the schematic diagrams and learn the operation of these amplifiers I understand the op amps but these amplifiers drive me crazy, well anyway if someone could help me I would appreciate greetings and good day
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When you turn up the volume, the currents at the outputs and correspondingly the supply input increase rapidly. The higher (dynamic) current levels may make the input voltage swing (vary). This voltage swing may cause an under-voltage or over-voltage protection to be invoked.
If you have an oscilloscope, try to look at the voltage swings at the power supply terminals.
Check the voltage supply on the amplifier itself. If it goes low, due to incorrect wiring, that will make it shut down.
I have already made the measurements and apparently it is okay sometimes, even if it is in low volume, it sounds like it wants to turn off and the fans do not work
"....the fans do not work" could indicate that it relies on the fans for cooling and as they do not work the temperature protection kicks in.
That's right, I'm looking for that part and verify and voltage does not reach any of the fans I'm not sure that's what feeds them
I have already checked the components that refer to the power supply of the fan and apparently they are fine and I try to excite the thermistors (attached photos) to see if the cooling system is activated and it is not activated, and take measurements of the thermistors in the 931 and 932 of first gives me a resistance of 1.3khoms and in the 881 that is the one that is next to the mosfets of exit only has 431ohms without giving it heat and with heat I see that it increases is normal in the first 2 decreases?
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Does it shut down with any speaker load or only when driven into its normal load (generally the lowest possible)?
with any load and I checked the output mosfets and are the originals are well, another amplifier of which I made a thread also towards the same and the last I think it would breack more And there I have paperweight, I do not want to happen what I take it easy because I'm still learning
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'Learning' using these or JL amplifiers is doing it the hard way. I understand if it's all you have to work on but they can be challenging.
You need to completely reassemble it and see if you can see which part of the power supply is being shut down. You can generally start with monitoring the voltage on the pins of the power supply driver IC to see which ones change as the amp shuts down.
You need to completely reassemble it and see if you can see which part of the power supply is being shut down. You can generally start with monitoring the voltage on the pins of the power supply driver IC to see which ones change as the amp shuts down.
I already tried it assembled mr. Perry Babin and I can not see what is going off first, the side where all the components go is inside yes I can measure the pulses of the upc494 and turn off is what I can see
If you want to repair it, you may have to make a set of temporary heatsinks out of aluminum stock. 1" x 3/8" works well for short tests or low power. Something more substantial may be needed if you have to drive it to high power for longer periods to make it shut down.
I already did tests outside and could not see what is going off first and I noticed that the output mosfets were of different batch, and replace them and I saw a few potentiometers near the connection of the subwoofer. What adjusts with these potentiometers?
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That's the balance for the output of the op-amp so it's likely used for the DC offset adjustment.
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