Sundown SAZ3000

[mike49504]

I got another one of theese amps in for repair. The problem im having with the amp is when i power it up i can hear the relay click on but no power light . also the amp has no output.

Here the voltages i have.

LM393
1:.11
2:2.56
3:.04
4:0
5:1.69
7:0.11
8:13.62


7815
1:0
2:0
3:-.08

7915
1:0
2:-24.7
3:-14.8

7805
1:-0.8
2:0
3:-.03

7905
1:0
2:-14.8
3:-4.8

KA78T12
1:-87.4
2:-119.7
3:-119.8

Any ideas on what to check?

 

[Perry Babin]

Do you have positive rail voltage? Defective rectifier?

 

[mike49504]

I have both + - rail voltages 119 volts

I have + 15 volts but -.04 for the negative regualted voltages

 

[Perry Babin]

There isn't any positive DC on either of the positive regulators. Follow the circuit back from leg 1 to see if there's a broken leg on a diode or some other break in the circuit.

 

[mike49504]

I found a broken capacitor The color bands on it are Yellow Black Brown
Is that the same thing as a 0.1 uf mylar cap? (104)

 

[Perry Babin]

It could be.

 

[mike49504]

The 7815 is also defective.

The one thats in the amp is marked Kia 7815A And the package style is where you dont need mica insulators behind it But the regulator is standing straight up in the middle of the board.

I have the following parts 7815act and a LM7815AC both T0 220 package will either of thoose work?

 

[Perry Babin]

I don't know what the 't' signifies but I'd suspect that either would work.

 

[mike49504]

Replaced the 7815 and still no + voltage on the regualtor so i tracked it back to the output driver board . Is there anything you know of on thoose boards that goes bad and makes it so theres no = voltage on the regulators?

 

[Perry Babin]

Do you have input voltage on the regulator but no output voltage?

Are you measuring the voltage with the black probe on the center leg of the regulator?

 

[mike49504]

I placed the black probe on the middle leg of the 7815

Leg1:-0.62

Leg3:-0.77

 

[Perry Babin]

There's no supply voltage. Follow the circuit back from pin 1 to see why you have no input voltage.

 

[mike49504]

If i place the black meter probe on ground I get the following

Leg1:-14.48
leg2:-13.86
leg3:-14.64

And on the op-amps i get

PIN4:-28.75

AND all other legs read -14.64

 

[Perry Babin]

It looks like you may have lost a ground somewhere.

Does this amp have 2 or 4 driver ICs on the driver board?

What's the circuit board designation of the regulator that you have no voltage on?

 

[mike49504]

Locatio of the 7815 is U4

 

[Perry Babin]

Which op-amp has -28 on pin 4?

 

[mike49504]

I replaced another cap in front of the regulator and now i have the following voltages on the 7815

1:23.64
3:14.78

Black probe on middle leg.

Now the 7915 has issues which i will replace the same cap and let you know what i come up with

 

[mike49504]

Ok heres what i have Now

7815
Leg1:23.72
Leg3:14.78

7915
Leg1:23.58
Leg3:8.71


ALL OP-AMPS TL072

1: -13.78
2:-13.78
3:-13.78
4:-23.84
5:-13.78
6:-13.78
7:-13.84
8:0.92

 

[Perry Babin]

I think the 7915 is right now. The ground pin on the 7915 is pin 1, not pin 2.

When you measured the voltage on the op-amps, where did you place the black probe?

 

[mike49504]

Ground terminal of amp