Hartke HA1200 main board removal

[bassliner50]

My beloved Hartke Kickback 10 (120 RMS Watts) was in an accident and the mid control knob in the EQ section has been sheered off. The schematic shows It is a 50K (linear taper) potentiometer ( VR104 ). I have had training and experience with soldering, schematics and circuits in general. I use this little amp all the time and want to replace that pot. Looking at the amp assembly leads me to think removal of the main board where that pot is mounted will be very difficult to remove because the power transistors are mounted to a heatsink and there is no obvious clearance to remove the circuit board from the steel housing assembly. Has anyone removed this board in order to perform service? Any advice would be greatly appreciated. I do not want to pull it apart, only to cause more damage....thanks..Roy

 

[Tom Schupbach]

Yes, and I have one in my shop right now with a bad volume pot.

1) Remove all the knobs, and jack nuts.
2 Remove the two Philips screws hold in the Direct Out jack.
3) Turn the amp around and remove the four Phillips screws from the middle of the heatsink. Leave the ones on the corners alone for a minute..
4) Remove the now loose transistor clamp rails (sliver U-channel)
5) Remove the four Phillip screws from the corners of the heatsink and pull it loose. Be carful, there is a red wire connected to the sink (it's a thermistor, don't break it!) that you need to remove.
6) Slide the chassis out from the rear where the heatsink was mounted.

Reassembly is the reverse of the above. Be sure to apply a new heatsink compound on the transistors prior to reattaching the heat sink.

Tom
HutchAmpMan.com

 

[Tom Schupbach]

Forgot something on the disassembly proceedure. So, step 5.1 would be to remove the four screws from the chassis. Two are on the corners and the other two are more in the center of the board. One of these is a chassis ground and will have a washer on it.

Tom