Amp PS working only under 13v

rrae

Member
2011-03-17 5:14 pm
Got this amp with blown PS.

Installed new PS fets - replaced to irf3205, new drivers BD140 and gate 47r resistors, and 494.

The problem is that when power supply voltage is under 13V, the power supply is working correctly, have good square drive signal. After increasing voltage, the drive signal gone bad (attached screenshot).
I tried to change KIA4558S to 4558L by leaving first leg unused, as the L version is 9pin, amp is going straight in protection - which is interesting, because as far as i remember, i have replaced S with L in that way and its worked.

Could it be that drive stage cant drive 3205?

494 when drive signal isOK
1 2.24
2 2.35
3 0.04
4 0.38
5 1.63
6 3.41
7 0.00
8 12.4
9 4.2
10 4.2
11 12.43
12 11.7
13 4.88
14 4.88
15 4.88
16 0.89


And the voltages when signal is bad
1 2.28
2 2.29
3 3.56
4 0.38
5 1.63
6 3.40
7 0.00
8 13.6
9 0.42
10 0.42
11 13.67
12 12.9
13 4.88
14 4.88
15 4.88
16 0.89

Only difference what i can see, that only pin number 3. is driving high.
 

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