Saturday, December 26, 2009

Fender "Champ" 5E1 is finished!

Well...mostly. Earlier this month I completed the assembly and began testing. Since then I added a switch for the feedback loop which runs from the output transformer back to the cathode of the 6V6GT. Since the power transformer does not have a center tap for the HV secondary winding, I wired a diode to each leg of HV windings and then tied the other end of the diodes to ground. The HV windings were then wired to the 5Y3 as per the schematic. It is my understanding that these diodes working with the 5Y3 provide full-wave rectification. I will post a revised schematic soon, but for now will include these photos. Don't forget to click on the photo to see a larger version. The first photo above shows the external components and where they came from.The Second photo shows the inside of the amp from the bottom. The wiring looks cluttered, and is, but I do have star or central ground and all grounded components are tied to this via the dark green wires. The other noise reduction effort involved using a cordless drill to wind the 6.3VAC heater wires which are light green. Since all of the components are pulled from scrap (except the output transformer, filter caps and cathode bias caps), I had to approximate values by combining parts. There are several resisters tied in series to achieve the proper resistance, and you can see two caps tied in parallel (yellow at bottom left) for the coupling from the 12AX7 plate to the 6V6GT grid.

The third picture shows the cabinet that I am using for now. This cabinet was given to me about 25 years ago by Frank Hilvert. THANK YOU FRANK! I believe it was built by a friend of his family. This unit was built with an outer screen which the amp is sitting on, while the actual speaker cabinet is lying on it's back in this photo.

It turns out that this was a folded horn design by Klipsch, which I located in a loudspeaker desing book from the '50s. This is visible in the forth picture.