Almost unused W19 tube tester.

Description

 

 

Series Number 31332

I am not a fan of "stories" with equipment, but this one has a story, and it's good story. It was sold new, by the Funke company, to a Norwegian Engineering company, called MORGENSTIERNE, in OSLO. Where it was just stored ever since, and almost never used, until the owner died in 1986. His son inherited all items, including the house, and he never did anything with the equipment. As his son retired 30 years later, he sold the house and the whole rest. This is how I got the tester.

 

 

I am very reluctant about these kind of stories, but it appeared all as the person told me, and besides I had the right to give it back in case of a problem. When I received it, Indeed the tester was unused for what I could see.

This card was with it, it has the original series number on it.

This is the delivery note. That little card was item 3. It is a pity there is no date on it, so we don't really know how old this tester is. However the blue book which is along with it, carries the tester's series number, and the latest adding in this book are dated 1962. So the tester is from 1962 or later.

Here you can see the only repair I needed to do. The resistor of 1000+95 Ohms has seen some heat. So I took it out, and the resistance values were perfect. I have repainted it with heat resistant grey paint, and put it back in.

Before switching on, I reformatted the capacitor, because I prefer to let the original parts in, when still good. However simply "switch on" such an old capacitor will damage it. At first it will resist no higher voltage than 50V, and draw several mA if you try. Then it works the same as charging a battery. So voltage goes up very slowly, as long as you give it charge current. Yet with capacitors this should be in the 50uA range. Then at 500V it more or less stopped "charging" and began to need more time. Yet when waiting long enough and at very little current, it would charge up to 550V and I stopped at that point.

Exactly 8.2uF as it should be

Capacitor leakage at 500V

Capacitor leakage at 550V (final result), with only 44uA (so little!) leakage current. Such a capacitor is of excellent quality. No need to replace.

As you can see from the side, this book was almost never used to look up a tube. It is clean as new.

The book is nicely up to date, even the higher ECC Numbers like ECC180...ECC962 are in there.

This is how I stored the cards, so to prevent sagging, and keep them clean. Sometimes when you see the absolute mess on Ebay, here you see how unused cards look like

The “finger switch” as you can see on the inside, is the heart of the W19, and the only part which will wear out. Though it is very robust, this is something which can still happen. The plastic wheels will scrape off some material, and when the axis will get some play also, contact problems will be the result, and inevitably, people start to bend the contact fingers, and in the end make only a mess. So such a switch needs to be completely removed and overhauled. Lifetime of this switch, as said is very high, but if used in a shop, like 25x per day for 25 years, there comes an end to it. Not to speak about army used W19, which sometimes were used 8 hours per day to re-test large safety stock on a yearly base. In such a case, also the pin contacts in the deck will need re adjustment. Which is very tedious work. With this tester all of this was not needed. The whole tester is almost never used. Really this was a wonderful find.

The mains transformer and it's voltage settings.

This is the stabilizer tube.

This tube serves also as on/off indicator via a hole in the panel meter, and it is a safety indicator for the total current draw of the whole circuit under test. Though this works in reverse, because it's a parallel stabilized circuit. So the brighter you see the "lamp" burn through the round hole in the panel meter, the less current draw there is. It is well dimensioned, because indeed above maximum allowed current draw, the lamp begins to burn so dim, you will not trust it any more.

Close up of the stabilizer tube. This tube, when heavily used will become somewhat silvery or grey on the glass inside. Though such a tune will normally deliver it's 150V, it's internal resistance is higher, meaning the load characteristic is not as intended any more. Some tubes react quite strong to that, and that would give a wrong reading. These original (Funke qualified GR150, not just any GR150) have a fully flat load characteristic when new. At end of life, the burning color gets darker, and the internal resistance goes up. Needless to day, this this is new condition.

Here is a test with the GR150DA

 

Please note, the lid is slightly offset to one side. It closes very good for the rest of it.