Are there schematics available for this amp, my guess is no.
The one I am working on is stuck in protect mode now. Originally it wouldn't output anything. I found a bunch of fractured solder joints. After repairing them it worked for 5 minutes then went into protect.
The outputs seem to measure ok, maybe I will pull them to make sure.
Any thoughts?
cory
The one I am working on is stuck in protect mode now. Originally it wouldn't output anything. I found a bunch of fractured solder joints. After repairing them it worked for 5 minutes then went into protect.
The outputs seem to measure ok, maybe I will pull them to make sure.
Any thoughts?
cory
Find which pin on the 494 is causing it to shut down and follow it back until you find the protection circuit that's causing the problem. If you disable the protection circuit, that would allow it to power up so you could determine if there is a fault in the audio circuit or if the protection circuit has the fault.
I wonder if my supply is to high, I had this problem before on a RF amp.
Here are my readings:
1) .3
2) 5
3) 4.8
4) .084
5) sawtooth
6) 3.43
7) 0
8) 15.6
9) 0
10) 0
11) 15.6
12) 14.8
13) 5
14) 5
15) 5
16) 12.5
Here are my readings:
1) .3
2) 5
3) 4.8
4) .084
5) sawtooth
6) 3.43
7) 0
8) 15.6
9) 0
10) 0
11) 15.6
12) 14.8
13) 5
14) 5
15) 5
16) 12.5
The supply voltage was part of the problem.
CH1 and CH2 still have an issue when I change the switch from Full/HPF/LPF. The amp will go into protect mode, my guess the switch is dirty.
CH3 and CH4 actually produce an output, but it looks sawtooth. This might have something to do with my backup supply, only capable of 600mA.
I will have to look for a couple of diodes to place in line with my supply, atleast drop the voltage some.
Either way this amp may end up in the scrap yard for parts, not worth putting a bunch of money into it.
CH1 and CH2 still have an issue when I change the switch from Full/HPF/LPF. The amp will go into protect mode, my guess the switch is dirty.
CH3 and CH4 actually produce an output, but it looks sawtooth. This might have something to do with my backup supply, only capable of 600mA.
I will have to look for a couple of diodes to place in line with my supply, atleast drop the voltage some.
Either way this amp may end up in the scrap yard for parts, not worth putting a bunch of money into it.
These budget amps rarely have over-voltage protection. The protection signal was coming into the IC on pin 16. You could follow that back to see what drives it.
Pin 16 leads to a 2904 op-amp. Running the supply at 13.5V, pin 7 of the op amp is low, running at 15.6V it drives pin 7 to 10.5V and the protect light comes on.
It must have over-voltage protection. Either way I need to modify my other supply to drop the voltage.
It must have over-voltage protection. Either way I need to modify my other supply to drop the voltage.
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