I'm working on an Old-school autotek and have rebuilt the PS new fets and gate resistors. The trouble I am having is, if i apply the remote the amp draws massive current and the tl494 does not generate pwm. But if I pulse the remote on and off a few times I get pwm and and the amp functions perfectly. I can even turn it off and on normally. But if I wait a few minutes, I have to pulse the remote again the same way. I have already changed the tl494. I have never run into this issue. Any ideas?
Are the PS FETs heating up when the current draw is excessive?
The TLx94 will switch modes (like it would if pin 13 was connected to ground) if pin 3 or 4 is pulled below the voltage on pin 7 (ground). This can sometimes happen when there is a problem with a soft-start circuit is used on pin 4.
The TLx94 will switch modes (like it would if pin 13 was connected to ground) if pin 3 or 4 is pulled below the voltage on pin 7 (ground). This can sometimes happen when there is a problem with a soft-start circuit is used on pin 4.
Yes the irfz44n's are getting hot and would definitely blow if left on. Also when it's drawing current like that the vcc on the 494 gets drawn down to around 5v.
Power up through a current limiter. Does it behave the same way?
Are all 4 banks of FETs heating up equally?
Are all 4 banks of FETs heating up equally?
So I set my dc power supply to 1a and same thing it just sits there drawing max current and will not cycle on.
1A may not be enough. What you need to do is limit the current to something where the amp will power up enough to check the functioning of the 494 IC. If you have the FETs clamped down, they can easily take 15 amps of current.
494 pinout with 12v input during excessive current draw.
1: 0.916v
2: 1.229v
3:0.130v
4:0.027v
5:1.184v
6:1.404v
7:0.027v
8:4.357v
9:2.960v
10:2.960v
11:4.357v
12:3.700v
13:2.777v
14:2.777v
15:2.777v
16:0.028v
1: 0.916v
2: 1.229v
3:0.130v
4:0.027v
5:1.184v
6:1.404v
7:0.027v
8:4.357v
9:2.960v
10:2.960v
11:4.357v
12:3.700v
13:2.777v
14:2.777v
15:2.777v
16:0.028v
The voltage is far lower than it should be. The 5v regulator (pin 14) is far too low for the IC to function correctly.
Do you have a TL594? The TL594 has undervoltage lockout that may help prevent it from powering up in this situation. Don't completely disassemble the amp to replace it if the amp is fully assembled.
The attached diagram may be similar to your amp.
Do you have a TL594? The TL594 has undervoltage lockout that may help prevent it from powering up in this situation. Don't completely disassemble the amp to replace it if the amp is fully assembled.
The attached diagram may be similar to your amp.