EICO 720 Restoration

Description

The following copied from the web...

The Eico 720 transmitter was introduced in 1958. According to the Eico ad in the 1959 Radio Amateur's Handbook, it was sold as a kit for $79.95 or wired at $119.95. It is designed for the 80 to 10 meter ham bands (including 11 meters). It uses a 6CL6 as an electron coupled Colpitts crystal oscillator, a 6AQ5 as a Class A buffer multiplier, a 6AQ5 as clamp tube and a GZ34 / 5AR4 rectifier. Its final RF amplifier is a 6146 for 90 watts plate power input on CW. It featured a heavy copper-plated chassis and a nice low-profile design. A switch on the rear panel selects either a phono jack connection for an external VFO or a front-panel crystal. An accessory octal power socket is provided on the rear panel for powering a VFO, connecting an antenna relay, and/or an external plate modulator. Eico sold a matching plate modulator, the 730 for $49.95 as a kit or $79.95 wired. The modulator cover, model E-5, was optional at $4.50.

Restoration

I bought my EICO 720 on Ebay several years ago and unfortunately it was not in great shape. Inside it looked good but the front panel was worn, there was one non-matching knob replacement and the meter bezel was scratched. I stripped it down taking off the front aluminum panel and it set on a shelf in the basement for those years waiting for me to have time or ambition to clean it up and put it back together. Meanwhile I restored a Johnson Ranger, a Heath SB200, and several other pieces. So this winter having finished those major restoration jobs and before I started another I decided to finish the EICO 720.

The restoration was ver straight forward and there is not a lot to say that can't be shown in the following photos. This is a nice rig and it works well. I replaced few parts and it performs excellently with full power output. Most of the tubes are original EICO. I seldom find problems with tubes in my restorations. I don't even bother checking them. The best check is the performance of the equipment and in the end this EICO 720 performed as good as new.

(Click any photo in this article to see a larger view)

The filter capacitors were replaced and a grounded 3 wire power cord was installed. Keeping things stock is nice but the one thing that should always be replaced in any restoration is the old non-grounded power cord

The original 50K 10W PA screen resistor was open and was replaced with two 25K 10W resistors and a new standoff.

The front panel jewels for the power and transmit lights were missing. I removed the incandescent bayonet bulbs and wired in a red and green LED with a diode and 330 ohm resistor in series. The photo above shows the wiring to the old sockets and below the leds through the front panel secured with silicone. The holes had to be drilled very slightly for the LED's to fit through.

The original plate RF choke was damaged and had to be replaced. I used a standard 2.5 mh leaded choke and added a new standoff for mounting.

The finished EICO 720 mounted in its case.

The front panel was removed and cleaned as best possible. There is some wear around the knobs. The meter face is scratched but certainly usable. I believe it is a standard size and a replacement cover could be found but I did not bother to do that. The copper plated chassis was in fairly good shape but around the front where it is exposed the copper plating was worn off in several areas and generally did not look good. I used several coats of copper leaf paint that I bought at a craft store and finished with a clear coat spray. The knobs were cleaned and polished. The white marker lines, which were almost completely gone, were repainted with titanium white acrylic paint also available at any craft store.

Manuals

I would be glad to answer any questions on my restoration. My email is good at QRZ. 73, Doug, WA3DSP

This page last updated 2/10/2014