Directed 1100 D

[mike49504]

I have this amp in for repair. When i was looking over the amp i noticed the LM361 was in backwards so i switched it around.

Amp powers up fine but has no audio and the caps circled get red hot within a min.

Lm361 voltages
1:6.77
2:.02
3:3.58
4:-3.13
5:0
6:-4.42
7:0
8:-2.35
9:.04
10:-4.14
11:-2.54
12:0
13:-2.35
14:-2.35

Wondering does this appear to be defective??

[Perry Babin]

What is the DC voltage on all of the legs of the two regulators (L781x/791x -- black probe on the secondary center tap)?

The LM361 is likely defective if it was installed backwards.

The LM361 appears to be the be the original IC, are you sure it was installed backwards?

What's the DC voltage with the black probe on pin 10 and the red probe on pin 14?

[mike49504]

781
1:25.54
2:5.26
3:6.71

791
1:5.26
2:-40.4
3:-17.42

The IC marked F16 was in backwards not sure if thats the lm361 or something different but the ic marked F16 reads

1:0.2
2:0.77
3:0.85
4:-5.27
5:0.56
6:0.56
7:0.56
8:6.40
9:0.55
10:0.54
11:0.54
12:0.56
13:0.43
14:0.56
15:0.59
16:-5.26

The other IC marked B52 from pin 10 to pin 14 reads 1.78 volts

[Perry Babin]

On the ICs are you looking at the notch or at the label orientation?

Does the notch in the IC match the notch in the silkscreen for the IC?

The F16 isn't the LM361. It's an MC14060.


There is a problem with the regulator voltages. The pins reading ~5v should read 0v. Is there an open to the secondary ground?

The 781x also appears to be defective (assuming that there isn't something drawing excessive current).

[mike49504]

The b52 Lm361 is the 16 pin Ic that was in backwards the notch was not lined up with the silk screen on the board.

Im looking at the notches on the chip.

Ill look for open traces not sure if it matters but the board is out of the sink