Wiring, Part 1: Preliminary Stuff

Pix here:

http://www.diycustomamps.com/images/...te/wiring_pt1/

This morning I did some preliminary work on the chassis to get it ready so that I can wire the circuit.

The Edcor output transformer has quick-disconnect tabs rather than flying leads so the first order of business was to make and attach flying leads to the OT. I found some quick disconnect connectors at McMaster-Carr when I was investigating using Edcor's transformers. I also bought some 600v, 20 ga. stranded wire in three colors: blue, brown and red. These are "standard" colors for plate and center tap leads on push pull transformers. The black and yellow wire is 300v, 18 ga. for the speaker leads. The quick disconnects use a dual crimping connection to hold the wire onto the lead.

The Edcor OT is slightly underrated for this application at 15w. The circuit puts out 18 watts, as indicated by the name of the circuit. Another thing I don't like about the Edcor OT is the lack of insulated flying leads. Using quick disconnects is inherently unsafe as there at least 300v on the plate and center tap leads. In one of the photos you'll notice that there is some red heat shrink covering two of the unused tabs. These tabs are ultralinear connections which are usually used in hifi amps. However, a few guitar amps have used UL taps most notably some Fender amps from the early 70s and some modern Dr. Z amps. There is also high voltage on these leads as well hence the heat shrink.

Once the leads are connected to the OT, it is a matter of twisting the black and yellow speaker jack leads and threading them through the grommet in the chassis. Then braiding the blue and brown plate and red center tap leads and threading them through the chassis. The wires are put into their proper places on the inside of the chassis as they they will be covered by the eyelet board and will be hard to get to.

The next step is to install the eyelet board. First I put the threaded hex standoffs in the chassis with lock washers to keep the board from vibrating loose. Next the board is put onto the standoffs and bolted down with machine screws and lock washers. I keep most of the machine screws loose until I line up the board to make sure it is positioned correctly.

Now that the board is installed, I can proceed to soldering all the flying leads into the circuit to finish up the amp. At this point I would estimate that the amp is about 50% done.

Stay tuned for more wiring.

tung