The AA8V 6AG7 Amplifier
by Greg Latta, AA8V

Construction Photos

Parts
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6AG7 Amplifier Pages:
  6AG7 Amplifier - Main Page and Exterior Photos  Tank Coil Construction Details
 Interior Photos of the Finished Amplifier  Schematic Diagrams and Circuit Descriptions
 Construction Photos  Testing And Preliminary Work
 Typical Operating Conditions  Why Use A 6AG7?

Construction Photos of the 6AG7 Amplifier:
Overall View Of The Parts Used In The Amplifier:
After the amplifier was tested and debugged on the original pie pan chassis, it was totally disassembled into individual parts in preparation for reassembly on a new chassis.

In this photo, the new chassis is in the back on the left and the power transformer is in the back on the right. The tubes are near the front on the right and the variable capacitors are near the middle of the photo.

Parts
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Chassis:
Since the original transmitter from which most of the parts came was built on a pie pan, I decided to do the same with the amplifier. However, I found a square cake pan with the same size as the original pie pan, and this gave me more room to mount parts. I paid about four dollars for the cake pan at a local surplus outlet. It is made of steel with a very tough cooking finish on it. It turned out to be the perfect chassis.

Chassis
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Restored Transformer:
The power transformer was rather rusted so it was cleaned and then airbrushed with Rustoleum gloss black paint. The wires were wrapped in masking tape during the process to keep paint from getting on them.

The transformer is a Stancor P-8010 universal type which has three secondaries rated as follows:
650V center tapped at 40mA (red)
5V center tapped at 2A (yellow)
6.3V center tapped at 2A (green)

The primary (black) is rated at 117V. Back in 1950 the transformer cost $5.75.

Transformer
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Punched And Drilled Chassis:
The first process in construction was to punch and drill the mounting holes in the chassis. Round holes up to 1/2" in diameter were made with a conventional power drill. Round holes larger than 1/2" were made using Greenlee chassis punches. Greenlee punches are expensive but they are well worth the money if you do a lot of construction.

Lacking a set of Greenlee punches, you can use an Adel nibbling tool to make the larger round holes. The Adel nibbling tool allows you to make any size or shape of hole once a 7/16" starter hole has been drilled. The rectangular cut-out for the power transformer in the back on the left was made using an Adel nibbling tool. I have used one of these tools for years and will swear by it!

The large round hole in the front of the photo is for the coil socket. The hole near the center is for the 6AG7, and the hole in the back at the right is for the 5Y3.

Punched Chassis - Top View
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Paint Stripped From Mounting Holes:
To ensure a good electrical connection, all of the paint must be removed from the mounting holes. This is most easily done with a small steel wire brush on a Dremel rotary tool. The Dremel tool is another indispensable tool for the hobbyist and I highly recommend one. Don't try to use a brass brush, it isn't hard enough. Use a steel or stainless steel brush. If you don't have a Dremel tool, then you can use a pocket knife to scrape the paint off of the mounting holes.

Punched Chassis - Bottom View
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Switches, Sockets, and Choke Mounted - Bottom View:
In this picture the front of the amplifier is at the top.

On the front panel, from left to right, the key jack, power switch, bandswitch, and pilot light have been mounted. The power supply filter choke has been mounted on the left side of the chassis, and the tube and coil sockets have also been mounted. 6-32 screws, lockwashers, and nuts were used to mount the choke and sockets.

On the back panel, at the bottom of the photo, the fuse holder, RCA input jack, and SO-239 output jack have been mounted. 4-40 hardware was used to mount the SO-239 output jack.

Switches and Sockets Mounted - Bottom View
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Switches, Sockets, and Choke Mounted - Top View:
This picture shows the amplifier at the same stage of construction as in the previous photo. All of the parts have been mounted on the chassis at this point except for the power transformer. The plate tuning capacitor is on the left and the loading capacitor is on the right. Connections to these capacitors will be through grommeted holes in the chassis.
Chassis and Variable Capacitors
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Power Supply Wired And Tested:
Once all of the switches, sockets, and variable capacitors were mounted on the chassis, the power transformer was mounted and the power supply was wired and tested. In this picture the power supply is completed and is functional. All other wiring is yet to be done.

Chassis With Power Supply Wired
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Power Supply Close-Up:
This is a close-up of the completed power supply. The high voltage output of the power supply is at the three lug terminal strip on the left in the photo. The 6AG7 socket is at the lower left and the 5Y3 socket is at the upper left. The green wire with a piece of heat shrink tuning on it is the 6.3V filament center tap, which is not used. The filter choke is at the lower right. Additional components are labeled in the picture below.

Wired Power Supply
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Power Supply Close Up With Notation:
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Power Supply Notated
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