Calibra DIGI 1600

[chrisg4]

I found it in a working amplifier... had the 22uf in my stock.

 

[chrisg4]

Hi Perry,

How would I fix the high side drive? I used the cap as u asked did not change the drive wave.

 

[Perry Babin]

Is the cap connected between the gate and source pads?

Are you probing the gate pad?

 

[chrisg4]

yes between gate and source

probe is on gate pads

 

[Perry Babin]

What value is the capacitor?

 

[chrisg4]

0.1uf

 

[Perry Babin]

Post a photo of the board showing the gate resistors, the FET pads, the loading capacitor and the probe placement.

 

[chrisg4]

Hi Perry,

think I have sorted the issue... I increased the value of the resistor connected to the high side pull down resistors.

 

[Perry Babin]

That looks better but without more details, I'm not sure what you did. You shouldn't have to modify from the original values unless there is another problem.

 

[chrisg4]

I agree but I was unable to find the original driver transistors, so I had to use substitutes. I used the JBL BP1200.1 circuit as a reference. My amp had R202 as 510 ohms. i changed to 910 ohm as per the JBL diagram.

 

[Perry Babin]

Were the original drivers blown?

What did you use as a sub?

 

[chrisg4]

I assume they did blow, as there was BD140's in the circuit.

I used below:

KSE340/KSE350
2SA1220A/2SC2690A

 

[Perry Babin]

Which one did you use?

In which locations (use BP1200 diagram designations)?

 

[chrisg4]

Q201 - KSE340
Q231 - KSE350
Q202 - 2SA1220A
Q203 - 2SA1220A
Q204 - 2SC2690A
Q205 - 2SC2690A

 

[Perry Babin]

I think the problem is that the 340/350 are too slow. I'd expect that, even with the resistor change, that they would run very hot.

What's the rail voltage in the amp?

 

[chrisg4]

Yes they are heating up... where do I measure the rails on this amp?

 

[Perry Babin]

Center legs of the rectifiers if they use center-tapped rectifiers.

 

[chrisg4]

I measured across the centre legs, I get 72v DC.

 

[Perry Babin]

72v across the positive and negative rectifiers or 72v from one rectifier to ground?

 

[chrisg4]

Across the positive and negative rectifiers. From ground to the center leg of the rectifiers i get no voltage reading but on the outer legs there is 35v present.