Crossfire TEK 150.2

[S Merlington]

Amp has no regulated voltages on op-amps..


As you can see someone has attempted to repair this already..

Both 1N4744A's test fine..

Does anyone know the value of the resistors that belong here??

Since someone has been in it before im not sure if theese resistors are the correct value..

I pulled R100 to check to see if it was in tolorance that was also replaced at some point with a 2.2k ohm..

Q101 and 201 were also pulled to check when photo was taken..

So im wondering if anyone know the correct values of the 2 resistors with arrows pointing to them and if the 2.2K in R100 spot is correct?

 

[Perry Babin]

I don't have anything on that amp but the CFA602 appears to be similar (attached). The two resistors with the arrows are 1.2k. R100 is in a different location here but you can see that the connection to the circuit appears to be the same. It's a 2.2k.

 

[S Merlington]

Thanks for the info..

On the 2.2K resistor i get 40 volts on 1 side of it but 0 volts on the other side that connects to the 1N4744's ..

So is there something else in theese amps that control the regulated voltages?

 

[Perry Babin]

From what I can see, the circuit is s simple shunt regulator. One end of each Zener will connect to a resistor that has its other terminal connected to the power supply rails. Those terminals of the Zeners/resistors will connect to the power supply pins of the op-amps.

The other legs of the Zeners will connect to the secondary ground.

One end of R100 appears to be connected to the rail. Is the other leg connected to the ground side of the Zener or to the op-amp side of the Zener?

 

[S Merlington]

The other leg is connected to the ground side of the zeners..

I dont get any voltage on the Zeners at all

 

[Perry Babin]

Are the 1.2k resistors within tolerance?

Are they getting hot?

 

[S Merlington]

The only value i had close to that was a 1k i stuck thoose in and they are brand new and within tolorance..

They remain cold to the touch..

The 2.2K gets hot

 

[Perry Babin]

Follow the traces back (for the legs not connected to the zeners) and see where they go. It's likely that they connect to the rectifiers. There may be a bad connection. On the 602, they appear to connect to 4 small rectifier diodes.

 

[S Merlington]

Theese also connect to 4 small rectifier diodes in the amp..

I reflowed solder to them and still no voltage..

I tested all 4 of theese diodes and all check good but they have no voltage on either side of them

 

[Perry Babin]

Do they connect to the transformer?

 

[S Merlington]

Ok i found the problem..

There was a bad solder connection on 1 of the fuse holders and somehow the controls 1 of the power supplys that feed the circuit