Of course. I have put some schematics on radiomuseum.org. Per digit they made four flip-flops out of two germanium transistors each. Four of those flip-flops go on a single pcb. They count to 10 and the overflow is carried on to the next digit. The outputs of the 4 flip-flops are sent to a simple digital-to-analog-converter (just a bunch of resistors) and the analog signal is fed to one of the moving coil meters. Special about the flip-flops is the way they count. With our present day knowledge, we would let the flip-flops represent a binary number, so the weights of the bits would be 1, 2, 4 and 8. That's called bcd-code. But that's not what they did. In this machine the weights of the bits are 1, 2, 4 and 2. Enough to count to 10, but it's a bit weird. I don't know why they did it this way, there must have been some sort of advantage. Another peculiar thing is that the stages are coupled through a capacitor, in other words, it's ac-coupled like in an audio amplifier and not dc-coupled as in modern day digital stuff. This must have been a left-over from the tube area. With a vacuum tube you must bridge the cap between an anode voltage of a couple of hundred volts to a grid voltage which is a few volt negative. The easiest way to do that is with a capacitor. The people who designed this machine in the 1950's were brilliant engineers, but they still thought like vacuum tube designers! Next to the flip-flops that are connected to the digits, there is another set of boards containing flip-flops for counting the time. A frequency count takes 0.1 second (or 1s or 10s) and they have to time that measurement. There is an ovenized crystal oscillator at 1MHz. That frequency is divided by 100 000 or by 1000 000 or by 10 000 000, so that takes another 7 boards with flip-flops.
Links:
www.radiomuseum.org/r/erres_electronic_counter_9908_03.html
www.vanderheem.info/meetentestapparatuur.html
www.vanderheem.info/foto.html second photo, front row "assortment 1958-1959"
vanderheem.com/
www.vanderheem.com/oud/product_images/prod_overige/prof_counter_9907_en_9908.pdf
I love esoteric test gear! this is a very interesting piece, can you shed light on its principle of operation?
Of course. I have put some schematics on radiomuseum.org.
Per digit they made four flip-flops out of two germanium transistors each. Four of those flip-flops go on a single pcb. They count to 10 and the overflow is carried on to the next digit. The outputs of the 4 flip-flops are sent to a simple digital-to-analog-converter (just a bunch of resistors) and the analog signal is fed to one of the moving coil meters. Special about the flip-flops is the way they count. With our present day knowledge, we would let the flip-flops represent a binary number, so the weights of the bits would be 1, 2, 4 and 8. That's called bcd-code. But that's not what they did. In this machine the weights of the bits are 1, 2, 4 and 2. Enough to count to 10, but it's a bit weird. I don't know why they did it this way, there must have been some sort of advantage.
Another peculiar thing is that the stages are coupled through a capacitor, in other words, it's ac-coupled like in an audio amplifier and not dc-coupled as in modern day digital stuff. This must have been a left-over from the tube area. With a vacuum tube you must bridge the cap between an anode voltage of a couple of hundred volts to a grid voltage which is a few volt negative. The easiest way to do that is with a capacitor. The people who designed this machine in the 1950's were brilliant engineers, but they still thought like vacuum tube designers!
Next to the flip-flops that are connected to the digits, there is another set of boards containing flip-flops for counting the time. A frequency count takes 0.1 second (or 1s or 10s) and they have to time that measurement. There is an ovenized crystal oscillator at 1MHz. That frequency is divided by 100 000 or by 1000 000 or by 10 000 000, so that takes another 7 boards with flip-flops.