So the 74hc74 came in today. I changed it and the protection remains.
Pins 494
1.) 4.887
2.) 3.025
3.) 4.827
New u1, u5, u2, q9-q18
Are both Q100, and Q110 D669A?
Class D card is still removed.
Pins 494
1.) 4.887
2.) 3.025
3.) 4.827
New u1, u5, u2, q9-q18
Are both Q100, and Q110 D669A?
Class D card is still removed.
Not sure what else to change.
I have changed everything out of desperation now. Voltage regulators all 3, all ic's q2,q100,q102,q101,q111, on and on. I've checked i believe every resistor on the board.
Next suggestion would be octocouplers?
I have changed everything out of desperation now. Voltage regulators all 3, all ic's q2,q100,q102,q101,q111, on and on. I've checked i believe every resistor on the board.
Next suggestion would be octocouplers?
Still no output from the 594c. If I lift pin 2 pin 3 goes low, protection light stays on. Which pin powers the drive of the ic? Pin 8, 11, only has .412vdc on them.
Have u tried reflowing the buss bars? I've seen multiple of that series of amps that needed them reflowed.
Okay, so it appears the soft start circuit is not supplying voltage to Pin 8 and Pin 11 of U2-TL594. Without this voltage, the drive is dead. I'm not sure how but your jumper between Q3 and Q6 caused Q5 to conduct and pass the B+ to the relay and U2, effectively bypassing the soft start circuit.
Remove the jumper and left Q15-2N4403 and power up if the amp has drive and the relay clicks Q15-2N4403.Q14,Q28-2N4401 or D30-1N5237 may have failed.
If still no Drive the suspects are Q3,Q6-2N4401,Q4-MPSA14 or Q5-2N4403
When the soft start circuit is restored, with a voltmeter, black probe on power ground, monitor the voltage at C1+ side while the amp powers up. You will see the voltage ramp up and latch(~12v) after a short delay and hear the relay click. This will tell you that the soft start are working properly.
Although I don't think this is the problem, it's common for the buss bar needing to have the solder reflowed and should be done if needed.
So I lifted Q15 We are in the right area the first time the protection light has been off. The relay engadged, NO DRIVE.
Replaced all the transistors Q3,Q6, Q4 i do not have MPSA14 New, so I switched with one from a parts board (Used) both test good.
The red protection light is finally off. If I place the Q15 back into curcuit. Back Into protection.
Replaced all the transistors Q3,Q6, Q4 i do not have MPSA14 New, so I switched with one from a parts board (Used) both test good.
The red protection light is finally off. If I place the Q15 back into curcuit. Back Into protection.
So after lefting Q15 you still don't have drive?
Try replacing U2-TL594 if you haven't already and left Q15.
I know you have your thumb on it, and just one or two parts away. Sorry if I've repeated something I don't have my laptop and working with my cell phone.
I replaced U2, and all the small transitors mention in post #34. With Q15 lifted
Pin 1 ) 4.779
Pin 2) 3.221
Pin 3) 4.842
No drive
Red led for protection is on
Lift q15
Red protection led is off
Pin 1) 4.777
Pin 2) 3.222
Pin 3) 4.836
No drive.
Pin 1 ) 4.779
Pin 2) 3.221
Pin 3) 4.842
No drive
Red led for protection is on
Lift q15
Red protection led is off
Pin 1) 4.777
Pin 2) 3.222
Pin 3) 4.836
No drive.
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I reflowed all the solder in the busbars for good measure. When I changed out Q3 to a different test transistor, a mje200. The amplifier then clicked very fast in and out of protection. The class d card was in curcuit along with the output transistors.
So I changed the the mspa14 with a closer transistor mspa06, the amplifier responded the same. Fast switching.