Musical Concepts or Qua-Co for DH 200

[z-adamson]

Before holding the board down to the heatsink it would be wise to solder in the 10 inch black wire to solder pad number 4. If you do this later it will be difficult. Had I soldered in the 10 inch black wire to number 4 prior to soldering the board to the heatsink wiring, it would have been difficult to solder numbers 8 and 9 to the heatsink wiring....so, now is the best time to do this.

New caps also soldered to the heatsink.

 

[z-adamson]

Now the board is bolted down and ready the whole module is ready to be installed to the chassis. After a little more cleanup of flux on the board.

 

[z-adamson]

To mount the module to the chassis and finish wiring the module to the chassis set it into position like so (see pic). Some I already wired in.....1 black and 1 red wire, so there are only 4 more wires to go.

 

[z-adamson]

Modules bolted to the chassis and fully wired in.

Next up: install filter caps.

 

[z-adamson]

Filter caps installed and loosely bolted to the chassis so that they can slide back and forth to allow for installation of the ground bar.

 

[z-adamson]

Pay special attention to this cap. It must be bent up to allow for clearance of the filter cap. I once did not pay attention to it and smashed it with the filter cap, damaging the leads, and had to replace it.

 

[z-adamson]

Now to solder everything to the star ground bar.

It's important to strip a good amount of insulation off of each wire going to star ground so that you get a good amount of wrap-around at the bar. This helps keep wires from moving around as you solder.

I found that wooden spacers at each end of the bar is good to keep heat from getting to the caps.

Lastly, It takes a LOT of heat to get solder to flow here. I found that a butane torch iron cranked up to full blast works best.

 

[z-adamson]

Soldered up. I'll let it cool, bolt the bar down then tighten the filter caps down to the chassis. Right now that are just finger-tight.

 

[z-adamson]

I find that a flat washer works much better than a serrated washer on the terminals for the ground bar because the serrated washer cause the bar to twist some as I torque the bolts down. A flat washer prevents that.

 

[z-adamson]

Fully assembled and ready to fire up on the bulb. I find that during it up with no fuses installed with a 25watt bulb first is good. This way I test only the power supply, not the driver boards. Then install fuses, one driver board at a time, setting bias as I go using a 60 watt bulb.

 

[z-adamson]

So here the amp is using without the fuses for the driver boards with the 25watt bulb. 47vdc at the filter caps.

 

[jwjarch]

Thanks for the great tutorial z-adamson!

 

[z-adamson]

Been running this amp with a 150watt bulb and bias set close to spec all week, off and on for hours at a time. Looking at brightness of the bulb and heatsink temps. All has been well.

 

[z-adamson]

Just for kicks, I will test other bulbs and check voltage at the filter caps.

Here is a 100watt bulb.

 

[z-adamson]

Here is what a 60watt bulb will do.

 

[z-adamson]

Here we have a 40watt bulb

 

[z-adamson]

And lastly, a 25watt bulb

 

[z-adamson]

And voltage on full 120v well power

 

[z-adamson]

So now you know which bulb to use, depending how much you want to choke down power supply voltage.

 

[z-adamson]

Now that I am done burning the amp in slowly in the bulb, time to idle it in 120v wall power and fine tune the adjustments. While doing this, I will monitor bias and offset in real-time with Simpson analog meters. I welded aluminum display cases for these gauges.

The spec for a hafler dh-2xx with a qua co kit is 225ma. Offset, spec is as close to zero as possible.