This amp had a pretty major power supply failure. It came to me from what appears to be a tech that gave up on it. Has new PS drivers and transistors, new output transistors and the output driver card appears to have had u1 and u2 replaced.
I am at a loss and hope to get direction. Currently I have the rectifiers removed and the amp powers up in protect. Here are the voltages I have on the TL494. Am I correct in believing pin 16 is high?
1. 0.015
2. 4.870
3. 4.697
4. 4.929
5. 1.481
6. 3.652
7. 0.011
8. 13.17
9. 0.011
10. 0.011
11. 13.17
12. 13.17
13. 4.961
14. 4.961
15. 4.961
16. 6.82
I am at a loss and hope to get direction. Currently I have the rectifiers removed and the amp powers up in protect. Here are the voltages I have on the TL494. Am I correct in believing pin 16 is high?
1. 0.015
2. 4.870
3. 4.697
4. 4.929
5. 1.481
6. 3.652
7. 0.011
8. 13.17
9. 0.011
10. 0.011
11. 13.17
12. 13.17
13. 4.961
14. 4.961
15. 4.961
16. 6.82
Post a good quality photo of the component side of the entire main board and the component side of any driver boards if no one can help.
If I’m able to get this working, I will rebuild the burnt area and repair the traces properly. This is how the amp came to me, I did find one of the wires reconnecting the gate resistors was in the wrong place. Fixing that did not seem to help though. What’s left of the burnt area doesn’t seem to be conductive.
No shorts on the output fets.
No change in behavior or tl494 voltage
Additionally, I have no significant voltages on u1, u4, u6, u8, u9 voltage regulators.
No change in behavior or tl494 voltage
Additionally, I have no significant voltages on u1, u4, u6, u8, u9 voltage regulators.
Pin 16 of the 494 has 88k ohms to ground.
Just noticed the protection light is on with or without power to the remote input.
Just noticed the protection light is on with or without power to the remote input.
From the information I have from a similar amp, pin 16 should be grounded. You may need to pull the socket to see if there is an open trace on the top of the board. Simply grounding pin 16 may not work if the trace is open on the top of the board and the trace leads to other points that need to be grounded.
Removed the header under the tl494 and the tl494 and there does not appear to be any traces or signs of any pads not connecting including pin 16. Reinstalled the 494 without header and all the voltages are still the same.
Also the protection light illuminates with power and ground only, and the the voltages on the 494 are the same with or without power applied to the remote.
Also the protection light illuminates with power and ground only, and the the voltages on the 494 are the same with or without power applied to the remote.
Sorry my hand writing isn’t the best, it it appears pin 16 is connected indirectly to pins 11/12 and 13/14/15 of the 494
additionally makes its way to the thermistor for the output fets, as well as, pins 5, 6 and 8 of the LM293 by the output driver card.
additionally makes its way to the thermistor for the output fets, as well as, pins 5, 6 and 8 of the LM293 by the output driver card.
OK. It's slightly different but I know what it is now.
What's the DC voltage on the pins of U5, near the audio driver board? Copy and paste the following list and fill in the blanks.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
What's the DC voltage on the pins of U5, near the audio driver board? Copy and paste the following list and fill in the blanks.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
This is taken at 13.27v dc limited to 3 amps and 0.05a current draw.
u5 is the LM293 shown in my drawing.
Pin 1: 11.39
Pin 2: 2.49
Pin 3: 10.64
Pin 4: 0.00
Pin 5: 1.65
Pin 6: 4.35
Pin 7: 0.12
Pin 8: 13.25
u5 is the LM293 shown in my drawing.
Pin 1: 11.39
Pin 2: 2.49
Pin 3: 10.64
Pin 4: 0.00
Pin 5: 1.65
Pin 6: 4.35
Pin 7: 0.12
Pin 8: 13.25
It does but it also maxes out my 5 amp supply and the ps fets start getting hot even with no power applied to the remote.
No, there are 16 ps fets total what seems to be 4 per bank. Each bank of 4 is driven by a 2sa1023(may or may not be original)
2 banks on opposite sides of the board are heating up.
I have identified the driver transistor they are connected to.
2 banks on opposite sides of the board are heating up.
I have identified the driver transistor they are connected to.