Replacing A Tuning Indicator Tube (EM 85) With An EM 80
By Bill Werzner

A few weeks ago I finished restoring a Grundig model 7085 AM FM stereo console that was manufactured in 1956/57. This radio required a good cleaning inside following my air compressor blasting away the heavy build up of dust. The switches and controls were oxidized due to age and a good spray down with DeoxIT got them working again. The tubes tested good, but a few capacitors had to be replaced – no surprise here! One remaining problem was the tuning indicator tube would not light up with that beautiful green color. A good EM 85 was almost impossible to find, and one that I did manage to locate on E Bay was way too expensive. A similar configured tube almost identical in size and appearance is the much more common and less expensive EM 80. I
had a couple of new EM 80 tubes in stock and found a number of them were available in Russia from a supplier on E Bay. The Russians also supply a 6E5 C tuning indicator that has a bright green target and is said to be good for ten thousand hours. It requires an eight pin tube socket for mounting and I have installed several in Zenith radios replacing 6E5s with great success. If they can make a beautiful 6E5 C maybe their EM 80s are equally good, so I placed an order for a half dozen. When they arrive I will evaluate them and report back!

I rewired the EM 85’s socket as shown below in a configuration to match the internal wiring of the EM 80. The tube lit up and responded beautifully when the radio was turned on.

  
  Should you encounter one of the foreign radios with a bad EM 85, simply rewire the nine pin base as shown for the EM 80, and that beautiful green glow will once again brighten up the dial.