Volfenhag ZX 7180

[S Merlington]

I replaced the outputs and output drivers Also replaced all power supply fets...

Amp is producing Rail voltages but not regualted voltages


I replaced the regulators but still nothing...

Heres what i get on the 494 are theese correct or is the amp in protection?


Pin 1:3.92
Pin 2:4.96
Pin 3:0.06
Pin 4:0.10
Pin 5:1.52
Pin 6:3.45
Pin 7:0.00
Pin 8:13.85
Pin 9:4.80
Pin 10:4.80
Pin 11:13.85
Pin 12:13.09
Pin 13:4.96
Pin 14:4.96
Pin 15:4.96
Pin 16:0.92

 

[Perry Babin]

This IC only controls rail voltage. Regulators sometimes have dedicated power supplies but most take power from the rails or from windings on the main power transformers.

If you have any more questions, post a photo of the board.

 

[S Merlington]

I will be posting pics up within the next 5 mins since i still cant get the amp to produce regulated voltages

 

[S Merlington]

Heres a couple of pics of the board

 

[Perry Babin]

The regulators are likely the two devices on the heatsinks near the fan. Do you have voltage on the large green resistors?

 

[S Merlington]

If i use the ground termianl as reference ..

On 1 side of the resistors I get 49 volts of rail

On the other side of them i get 0.8 volts

And on 1 measured directly across it i get 49 volts

Other 1 i get -49 volts

 

[Perry Babin]

Are they out of tolerance or open?

If not, I'd expect them to be VERY hot.

 

[S Merlington]

They both get very hot..

They measure 0.558K ohms


I believe they are 560 ohms color bands are Green ,Blue,Brown,Gold

 

[ultra]

It also seems that these two rail caps are swollen. You may need to replace them.

 

[Perry Babin]

Do the emitters of those two transistors go to the power supply pins of the op-amps?

Can you post a tighter shot of both sides (front/back) of one of the transistors?

 

[S Merlington]

I will charge my camera and get better pics..

The Rail caps are fine its just the plastic dome on top that makes them appear swollen

 

[S Merlington]

Yes they go to a D1302 transistor the to the supply pins

 

[Perry Babin]

Check the Zener diodes near those standing transistors.

 

[S Merlington]

both diodes check fine out of the board

 

[Perry Babin]

With the zeners back in the circuit, what is the DC voltage on all 3 legs of each of the regulator transistors?

 

[S Merlington]

TIP42C

Leg 1:-1.53
Leg 2:-0.88
Leg 3:-0.85

TIP41C
Leg 1:-0.13
Leg 2:-0.77
Leg 3:-0.83

 

[Perry Babin]

Remove the transistors and post the voltage on the pads.

 

[S Merlington]

After reoving the transistors heres what i get..

TIP42C

Pad 1:-16.06
Pad 2:-49.9
Pad 3:-0.8

TIP41C

Pad 1:14.25
Pad 2:48.4
Pad 3:-0.8

 

[Perry Babin]

Those are about what I'd expect. Are the transistors leaky/shorted?

 

[S Merlington]

They both test good..

I can replace them and see what i come up with..