Okay, so it's somewhat different than most of my other sets, but when I found this Zenith receiver with its original manual in August 2003. The price was right and I didn't have any communications receivers in my collection. Besides, it's a Zenith and it's the only communications receiver of its type manufactured by Zenith, excluding the famous Trans-Oceanic portable line manufactured from 1941 until 1982.
This set is an AC powered, 5 tube receiver. It covers shortwave (SW) frequencies from 1.7 mc to 30 MC, broadcast (AM) frequencies from 500 KC to 1700 KC, and longwave (LW) frequencies from 150 KC to 400KC. When I got this set, it was all there and in fairly good condition. Before testing the set's functionality, I replaced the electrolytic capacitors to protect the power transformer. I also replaced a few of the molded paper capacitors underneath the chassis. Even if they weren't bad, these paper capacitors are notorious for being leaky so replacing them now would only prevent problems in the future. I left the original ceramic capacitors in place since they are usually reliable. I tested the tubes, all of which were the original Zenith tubes. They were all good, so none needed replacing. Next came contact cleaner inside the tube sockets, tuner, and all the switches. One dial lamp needed replacing and the set was ready for power. I applied power and switched the set over to the broadcast band. I was able to tune in several local stations, so that was an encouraging sign. I attached a 15 foot length of wire to the antenna terminal and switched over to the first shortwave band. Several stations from all over the world came in as I turned the dial. This was a positive sign, so I did the same on the other bands all with positive results. I decided the set was performing really well and switched over to cleaning the cabinet.
This set is enclosed in an all metal cabinet. The top, sides, and bottom all have a woodgrain texture. All the cabinet needed was a good cleaning. The chrome on the front were polished using chrome wheel polish and the results were good. I put the chassis back in the cabinet and now I listen to foreign broadcasts on this set some evenings. This was a relatively easy restoration.
The Zenith model M660A was introduced in mid 1964 as a competitor to other communications receiver manufacturers such as Hallicrafters. The set was not a big seller and was discontinued early in the 1967 model year. My M660A is stamped "APR 21 1965" inside the cabinet.