Team Cactus 7kw

[Perry Babin]

The 7815 appears to be installed backwards. If so, it's likely been damaged.

 

[mike49504]

Replaced it

Leg1:21.38

Leg3: 14.97

7805

Leg1:14.95

Leg3:5.02

 

[Perry Babin]

That looks better.

 

[mike49504]

So the problem is likely on the Output driver board? On the middle row of pins at 1 end the pin connects to an ic (U4) and at the other end the pin connects to a diode

 

[Perry Babin]

There was a problem with the regulator. There may be no other problem.

 

[mike49504]

Powerd up the amp and now it has 93 volts of dc on the outputs any ideas?

 

[mike49504]

Ok took care of the Dc on the outputs issue. Amp power up and plays audio but it has distorted audio and and hear a squeal through the test speaker. Any ideas?

 

[mike49504]

Ok found a problem In the power supply section Resistor R166 is very badly burnt anyone know the value of this?

 

[Perry Babin]

1K

It connects between the secondary ground and the heatsink (when the board is screwed down). There shouldn't be any voltage (AC or DC) on either end of it.

 

[mike49504]

Ok reinstalled A1381 and C1027 amp powers up and
produces audio but has squealing through test sub Any ideas?

 

[mike49504]

Would an output inductor cause squeal on the outputs? I noticed when i recieved this amp in for repair that 1 of the output inductors was loose and had been removed from the board at one point when i get the squealing that same inductor also squeals . Or could it possibly be something else?

 

[Perry Babin]

If the inductor is intermittently shorted, it may cause it to do strange things.

Is there anything that you can push on or move that makes it squeal.

 

[mike49504]

Only thing i can see is that inductor when i tap it it makes it worse and i can hear the inductor squealing and it sounds like its popping .
If i remove it from the board amp will still produce audio but the output still squeals is that because its removed or because there is another problem?

 

[Perry Babin]

Is it possible that there's an intermittent connection on that inductor and when the connection is open, the amp squeals? The vias may have been ripped from the amp when it was initially removed.

 

[mike49504]

I reflowed the solder on it didnt make it better But if i twist or pull on it it does make the squealing worse. Si if the vias was ripped from the amp when it was removed does that make the amp unrepairable?

 

[Perry Babin]

Does it always squeal when the inductor is out of the amp?

 

[mike49504]

The squealing is still present with it out of the amp but not as bad

 

[Perry Babin]

Can you see the squealing on the output (with the scope)?

 

[mike49504]

Yes . I also noticed there are 4 22uf 250v caps near the output inductors that are popping when i increase the input signal

 

[Perry Babin]

I had an amp with 'success' brand caps that were shorting intermittently and when it happened, they popped.