Arrival, teardown and function test of the Rohde & Schwarz counter FER BN 4721
Today, the FER BN 4721 counter arrived! It was well packed.
I'd asked the seller to pack it well because of the tubes and he kept his promise.
What a beauty! And the inside is so clean, nearly no rust! That is a dust puppy on the lower right.
One of the previous owner was obviously Telefunken.
Below one can see the electromechanical counter. And it has a chicken head knob!
So, what's on the inside?
Overview and the back of the electromechanical counter.
The mains fuse, by setting it into a different holder one can select the mains voltage.
And we have a datecode. I think the last digits are 58 or 59 because I've found on an
electrolytic capacitor a datecode from 1958.
Next to the fuse we have a rectifier from AEG.
Some electrolytic capacitors from Bosch, all are "tropenfest", so one can use them in the jungle.
This is an overview of the backside.
Overview of the bottom side. With detailed views to the parts.
Aren't they beautiful?
Look! The Andrew-Sisters! And their manager, Mr. Selenium Rectifier!
Does it work? Yes, except for a sometimes hanging electromechanical counter. It is probably worn out.
The sensitivity of this counter is big enough, that it was sufficent to attach a cable to a metal part
of my LED lamp and then it is picking up the 50Hz hum and count it.
Please see also the attached video below. If you are listening carefully,
you can hear the clicking noise from the electromechanical counter.
This counter is really a fine piece of art. I do like it very much and given its age,
it is in a very good condition. It has a remarkable amount of electrolytic caps in it,
which were very expensive back in the days. Also the amount of tubes used in it
is very impressive. The counting tubes used (they are ET1) saved a lot of additional tubes.
For example, they do not need an additional vacuum tube flip-flop for storage, otherwise
the amount of tubes used could be easily doubled.
I will clean it but I'm not sure, if I should replace the caps. Since I've bought it
mainly to prevent tube vultures from getting it in their dirty finges¹, I think, I'll give
it to a friend of mine which is running a museum for old and rare devices.
I hope, you've enjoyed this little teardown.
Thank you for watching.
¹And it is a very cool counter!
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