Posted: Sep Sat 29, am. I've downloaded the instruction manual for this piece of equipment, but I can't seem to make it work right. Can someone tell me generally how to use the thing? In testing the value of a capacitor, what should the voltage selector be set at? How about the range factor pot?

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It also can check a capacitor under its actual operating voltage, a feature that makes it very handy for restoring vintage tube radios and TVs. After cleaning the controls and replacing a few capacitors, it works like a champ. Below is a photo of the device in action.

In the previous photo, I'm measuring a capacitor's value. The "orange drop" type cap is mounted in test terminals at the right. The Range selector is set to the appropriate capacitance range. The green "magic eye" indicator is seen at the upper right.

As you turn the big middle pointer back and forth, the magic eye will be closed for most incorrect values in the chosen range. When you reach the cap's actual value, the dark crescent in the eye opens up, as shown here. In this case, the value on the B's scale matches the value marked on the cap.

At lower left is the Voltage control. When checking a capacitor for leakage, you begin with this at zero and then increase it to the capacitor's rated working voltage. As the capacitor charges up, you will see the crescent close momentarily and then reopen when the cap reaches full charge. If the crescent remains closed all the way when you reach the rated voltage, the cap is too leaky to use. Testing a capacitor under voltage is what makes this bridge so valuable.

A modern multimeter may test capacitance, but the voltage that it applies is miniscule compared to what the capacitor will experience in a tube radio or TV. Old caps might look fine using a modern multimeter, yet leak badly at operating voltage.

Only a checker of this type can provide a meaningful real-world test. Before testing a capacitor in a radio or TV, you must disconnect one of its leads. Otherwise, you are testing that capacitor plus everything else that it's connected to, a meaningless exercise. The left side of the panel has a second set of terminals labeled Comparator. When you turn the Range control to Comparator, you can connect a component of known value to these terminals and then compare the value of a component connected to the right terminals.

This is an alternative to using the B's internal circuitry for comparison. One case where you might do this is where precision is important. In the left terminals you would connect a component with exactly the right value. In the right terminals you would test all of the replacements in your parts bin and select the one whose value is closest.

The B can do various other things, but since the manual is available at the BAMA archive, I won't describe its other features in detail. Like any s tube device, the B should be restored before use. This typically means cleaning its controls with DeOxit and replacing its paper and electrolytic capacitors. Here's a rear view of the chassis showing its two tubes, a 6X5 power rectifier and the magic eye.

EICO products were available either as a kit or pre-assembled from the factory. In the previous photo, I had already replaced some of the old paper capacitors with new yellow ones. The next photo shows two old electrolytics that will also need replacement.

The big tan one 8 mfd has an unusually high voltage rating: volts. As you can learn in my capacitor replacement article, wiring two identical capacitors in series results in half the capacitance and double the voltage rating. To equalize the voltage in the pair, I'll wire a K resistor in parallel with each one. This creates an mfd cap with a volt rating, more than adequate. In the next photo, I have removed both electrolytics for replacement.

Obscured behind the potentiometer was the last paper capacitor, which I'm just about to replace. One end has been snipped free, and I stretched out the cap to reach the other end. The big pointer is held to its shaft with a setscrew.

If, after recapping, your pointer appears to be off by the same amount across the scale, just loosen the screw and adjust it.

That's the only calibration possible with this rather simple device. Apart from tube failure, not much else can go wrong with this simple device. The B is a "service grade" tester, meaning that it's accurate enough for everyday radio and TV repair, but it's less accurate than a laboratory-grade instrument. That's quite a bit of latitude.

If higher precision is desired, you can try the Comparator function as noted earlier. If you need very high precision, then you should not be using a service-grade tester in the first place. The failure rate for old paper and electrolytic capacitors is so high that testing them is a waste of time. If they haven't already failed, they'll croak before long, and you'll find yourself hauling your "restored" radio or TV back onto the workbench.

As the saying goes, I generally test old papers and electrolytics by listening for that satisfying Clang! This "kill 'em all" rule is not applicable to old mica or ceramic caps, whose reliability is generally much better. Furthermore, micas and ceramics are often found in tuned circuits where precision is crucial. If you "shotgun" all of them, you may be forced to realign a radio or TV that otherwise wouldn't have needed that exacting operation.

My recapping article has much more to say about identifying and replacing old caps. Even mica caps can fail, however, and as time goes by, I seem to be finding more and more of them that need replacement.

With the EICO or a comparable tester, I can check suspect micas individually, under their rated operating voltage. Like other vintage test equipment, the B was not manufactured to modern safety standards.

To avoid shocks when testing components in an old radio or TV, you should use an isolation transformer and take other common-sense precautions. Phil's Old Radios:. Refurbishing the B Like any s tube device, the B should be restored before use.


Eico 950b Construction Manual

Recently I have begun what might be the start of a nostalgic journey in vacuum tubes. I credit this addiction to Paul of Mr. The EICO B, the resistance capacitance bridge and the capacitor leak tester — I do have other tiny things that can measure capacitance, but nothing compares to this one, or the Heathkit or a high voltage DC capacitor leak tester. It is a vacuum tube scope and I need a leak tester to check the caps in it. But I digress. I was looking for a decent heathkit or the EICO to help me restore it when I stumbled upon this little treasure. Sometimes, in the process of looking for something, you come across a few folks, who possessed a wide spectrum of skills and abilities.


EICO 950B – Repair/Restoration

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