Boston Acoustics GTA 800m

[outoftheblue]

Ok. I installed a 2n6491 (reversed from the original transistor).

I still get the red led for protection mode as soon as I turn on the remote.

Here are the voltages at the 2n6491 pins.

Remote On:
B - 12.05
C - 11.08
E - 12.71

Remote Off:
B - 12.68
C - 0.08
E - 13.06

 

[outoftheblue]

Voltages on TL494 pins:
1 - 2.69v
2 - 0.14v
3 - 0.09v
4 - 0.04v
5 - 1.46v
6 - 3.62v
7 - 0v
8 - 1.47v
9 - 0.36v
10 - 0.36v
11 - 1.46v
12 - 11.03v
13 - 4.95v
14 - 4.95v
15 - 7.21v
16 - 4.95v

 

[Perry Babin]

You need to determine why you don't have 12v on pins 8 and 11. I'm assuming that pins 9 and 10 are used to drive the FETs.

In the future, avoid using hyphens as separators. They can be mistaken for a negative sign.

 

[outoftheblue]

I found that my replacement parts for the 2sa1266 drivers were not pin compatible as I had thought. So I pulled the transistors and fired it up without the two driver transistors. The status Led is now switching back and forth quickly between blue and red.

Here are the DC voltages on the TL494 pins:
pin 1: 2.69v
pin 2: 0.14v
pin 3: 0.15v
pin 4: 0.04v
pin 5: 1.46v
pin 6: 3.64v
pin 7: 0v
pin 8: 5.34v
pin 9: 2.05v
pin 10: 2.05v
pin 11: 5.34v
pin 12: 8.17-12.25v (jumping)
pin 13: 4.95v
pin 14: 4.95v
pin 15: 6.74v
pin 16: 4.95v
(all measurements except for 0v and 4.95v are jumping around)

I am currently powering the amp through a very small battery charger.

 

[Perry Babin]

Without the PNP drivers, the amp is likely drawing excessive current.

 

[outoftheblue]

I replaced the PNP drivers using the correct pin orientation (base and collector were switched) and it works now.

I'm guessing that mistake caused Q1 (the PNP that provides the TL494 with 12v) to fail by drawing too much current.

Thank you very much for your help Perry.