Monday, March 25, 2013

Bandmaster part 2: Wiring The Backside Of The Board

Once I had the components dry mounted on the front of the board it was time to do the back side wiring. For the uninitiated this is the wiring that  is sandwiched between the insulation board and the back side of the component board, and there are more than a few wires. They've got to be installed and soldered to the eyelets unless you want to take it all apart again.

But what to do? The Mojotone manual has a picture of what it should look like more or less but I was not really satisfied with it. Then the solution came to me. The Weber layout diagram image was acquired on my computer and reversed so it showed the hatched lines for the back side wiring as if I was looking down on it from above.

Here you can see what I used to run the back side wiring.

Once the wiring was run I finished soldering up the components and the flying leads. At this point I did not know how long they'd have to be so all of them were 12 inches long. It required an order for some more Stewart Macdonald yellow waxed pushback wiring.

Taking the layout diagram and schematic I then made a map of every termination point on the assembled board and checked every lead for continuity and arrival at the proper destination. Some of the wiring came out from under the board but I moved it to the top for ease of maintenance should it ever need repair. Here's one fellow's assembled board which I used as a model.

And here's mine, installed in the chassis. It's not quite as pretty but taking the time to validate every connection for continuity and proper hookup paid dividends because  it worked as advertised when I powered it up. One thing i did not want were screwups that required a disassembly.

Once the board was in place all it required was stitching up the connections that I had tagged according to the map I made. As I had already wired up the controls and power supply previously, once I wired up the inputs and speaker jacks it fired right up.  With a 5R4 rectifier and a pair of 6L6GCs from the House of Ruby, I got a measured 430 plate volts and set the bias at 40 ma.

The next adventure will be when the weather gets warm enough to coat and seal the tweed covering and final install the chassis.

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