Eico667 troubleshooting

Posted on Feb 6, 2014

Here is the schematic from the Eico 667 tube tester. It is very similar to the 666, except now there are a pair of extra levers, and a few test sockets are missing. But the meat and potatoes are identical. If you are planning to restore your 667 to peak operating condition, here are a few pointers. Replace the selenium diodes CR1 and CR2. I rivet

Eico667 troubleshooting
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in a small terminal strip, using the mounting hole from the `old` diodes. It is now easy enough to install 1N4007 diodes across the terminal strip. While you are at it, replace filter capacitors C1 and C2. Since modern-day capacitors are much smaller than their ancestors, I replace C1 with a 22uF/150VDC or possibly a 47uF/150VDC capacitor, while C2 is now a 22uF/25VDC capacitor. Typically I use whatever I happen to have on hand. Carefully check the calibration potentiometers R7 and R18. If you are having any difficulties calibrating your tester, change these potentiometers! Replace them with any quality 100K linear-taper potentiometer. I make sure I use a control with a nylon shaft, and avoid those with split and/or splined shafts. If necessary, I also cut a notch in the top of the shaft, to facilitate using a small screwdriver for any adjustments. Eico used very poor quality controls here, and they are prone to failure. When doing the calibrating for the Line Adjust, I will set it so `High Noon` gives me a reading of 6. 3VAC with a 6L6 inserted in the socket! This may seem obvious, but I sometimes carefully calibrate the Line Adjust exactly as the manual describes, and I end up testing a 6L6 with barely 6VAC on the filaments. I choose a 6L6 as opposed to a 6V6 because the filament draw is higher, and I want to be sure this procedure is done under a decent sized load! You can measure the filament voltage while testing say a...

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