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EICO 667 Tube and Transistor Tester

  Les Satterfield   USA Flag

EICO 667 Dynamic Conductance Tube and Transistor Tester

"The EICO Model 667 Dynamic Conductance Tube and Transistor Tester is one of the first thoroughly practical service instruments able to test both tubes and transistors. Among its advantages are rapid and simple operation, close simulation of actual tube operating conditions, and unexcelled thoroughness and accuracy of test. The outstanding mechanical design and layout, coupled with components carefully selected for ruggedness, makes the Model 667 extremely well-suited for hard usage of daily work service."
    - From the instructions manual for EICO Model 667.

EICO 667 Dynamic Conductance Tube and Transistor Tester

Photograph 1: EICO 667 Dynamic Conductance Tube and Transistor Tester

Tube testers were a part of most every TV and radio service person's tool kit. These were extremely useful for identifying a bad or weak tube and was a better option than simply swapping tubes over and over; which required switching off the set, replacing a tube, switching the set back on to see if that fixed it. This can really be tedious if there are a lot of tubes involved. Tube testers gave the technician the ability to go through each tube individually and identify the weak or bad tubes, or if none showed bad then he knew to look deeper. Because these were to be used in the field they were built rugged, usually having good solid metal casing made from heavy gauge steel. The controls had to be robust to stand up to daily use. The weak points were necessarily the sockets. Most units were designed so the sockets could be somewhat easily replaced.

Now days, tube testers have become collector's items, though a few do still buy them for their intended purposes, namely the DIYers. Because of their "collectable" value, some sellers are set on making money from cleaning these up and selling them, mostly on auction sites. Some units have been completely rebuilt and put up for auction. You often see these selling for several hundred dollars (US) up to a few thousand dollars (US). You do not need to put out that kind of money. Don't get fooled in to believing these "restored" units are any better than one that is simply being sold in good working condition. That's all you really need to look for. The one pictured here I obtained for around $200US. It is in excellent condition and has not had any restoration done at all.

EICO 667 Tube and Transistor Tester - Inside View

Photograph 2: Inside View - EICO 667 Tube and Transistor Tester

The EICO 667 is basically the same as the 666 Model, so the information here generally applies equally. These testers are, unlike say the EICO 625 and EICO 628 tube testers, capable of true dynamic conductance testing rather than simple emission testing. Emission testing will tell you that the various elements will pass current or detect shorting, however the tester is not simulating typical biasing. Dynamic testing is closer to actual operation in a typical circuit. The EICO 666 and 667 do allow you to at least do rudimentary tube matching. The differences between the EICO 666 and 667 are in the tube types they were designed to handle. The 667 is a newer model that incorporates the ability to test the 12 pin compactrons . Unlike the EICO 666, the 667 can not natively test older 4, 5, and 6 pin septal tubes with out an adapter (model 615 adapter). Additionally, the 667 can test nuvistors, pilot lamps and miniature "Christmas" lights. Both models test sub-miniature tubes up to 8 pins, transistors, regulators, ballast lamps, electron ray (magic eye) tubes and, with an adapter, color and B/W CRTs.

Using the tester is a relatively simple process. First, setup the line voltage. For the tester to be accurate, you do need to "tune" the tester to your line voltage. Simple; press the line push button and at the same time rotate the "line" control until the needle is resting squarely on the vertical center line on the line adjust scale. From that point, just follow the tube chart. In this picture, I am testing a 6T9 compactron's pentode section. The slider switches select the particular type of element per pin. Set the grid and plate adjustment accordingly with the 2 VRs, left and right respectively. (The 0-100 reference is not voltage but rather a % of fine adjustment for the setting of the "V" and "S" selectors. Actual voltages for Plate and Grid are set-up with the "V" selector. The "Grid" adjustment works in tandem with the "V" selector to fine adjust grid voltage. The "Plate" adjustment works in tandem with the "S" selector, which sets a shunt that is applied across the meter.) Then, referring to the chart, switch through the appropriate pins using the push latch buttons above the sliders, this checks for shorts. One of the buttons is the cathode (which button depends on the particular tube and is indicated by an underline in the chart). You can check H-K shorts. Then with the button indicated for the merit test pressed, you can actuate the "Merit" lever to see how good your tube is. A desirable reading is anywhere in the green "GOOD" marker. The percent value can read higher than 100% due to manufacturing tolerances of the tube under test, and you can generally use that reading for "matching". One important note: testers are not to be considered the "end-all" test for operability. This tester will simply tell you the quality of a tube (or transistor) under specific circuit parameters. As a general rule, tubes that test well in to the "Good" range should perform very well where as tubes the read in the "?" (weak) or even high in the "Replace" margin could perform relatively well. The best test is always in the actual circuit.

EICO 667 Dynamic Conductance Tube and Transistor Tester

Photograph 3: EICO 667 Dynamic Conductance Tube and Transistor Tester

Caring for your tester is easy. You want to keep it clean and store it in a nice dry location. Humid locations will cause corrosion of the switch contacts and of the variable adjusters. Do not use wool or cotton to clean the meter face (or any other material that can cause static build up on the plastic cover). The meter is extremely sensitive to static build up and can give you erroneous readings. Avoid using harsh chemicals to clean the meter face. Simple water and mild detergent on a damp lint free, static free towel will suffice. I recommend a soft paper towel. Occasionally clean the contacts of the switches and sockets with a good quality contact cleaner, avoiding those that could be damaging to plastic - read the label! With proper care, these units can last a good long time. Please post your questions, comments and additional information on the EICO Model 666 and 667 tube testers thread on the forum.

Instructions Manual and Tube Data Chart - EICO 667 Tube Tester

The instructions manual and tube data roll chart are from the BAMA web site. Check out their archives for more hard to find tube manuals.