EMG 12563 pulse generator tear down

[dzseki]

I figured this may be interesting for you, as you will not see such thing popping up on international auction sites.

Factory background: EMG stands for „Elektronikus Mérőműszerek Gyára” in english it would be like „Electronic Test Equipment Factory”, was a hungarian producer of test equipment. The company had its roots back to the 1920’s, after WWII it was reorganized and expanded. The production portfolio was rather broad and the factory served the eastern-block markets, in Hungary this was the biggest TE factory and also the most regarded. Most of the products were functional copies of western instruments, functional by means they wanted to keep up with them. As time went by this was harder and harder of course. To be fair they had to work from components mostly those could be sourced/manufactured in the eastern block, so where HP or Tektronix could have custom ASICS, engineers at EMG had to solve the problem only by using generic discrete components. After the eastern block dissolved in ~1990 the company went bankrupt in short way, no surprise, because by that time the technological lag was 15-20 years behind state of the art. Nevertheless they had some quite usable equipments. Because of the relatively low used price and the (mostly) discrete construction they are very popular hobby instruments.

Here you can find a shortform brochure about instrument lineup from 1982.
Brochure

I scored this instrument years ago for only 35USD on a local auction site, it was meant to be completely dead but it came with original service manual, so I figured why not? "Unfortunately" it was misdiagnosed as it is working fine since the first time I powered it up. All the knobs were broken/missing though.

It is an ECL pulse generator with repetition frequency between 10kHz-300MHz, minimum pulse width is 4ns, maximum output voltage is 2.5Vpp terminated. The rise time of the output is supposed to be less than 1ns. I also have/had several other instruments (oscilloscopes, function generator etc.) from them, and to be honest they are medicore performers, the specifications are not outstanding, and they are just able to meet them. With this unit my experience was quite the opposite however, because I found out that not only all specifications are easily met, but the rise time of the output is about 400ps, which makes this instrument comparable even to western counterparts.

This particular unit is a rather lately produced one, there are several components dated to 1989 november or even newer. The design however dates back to late 70’s.

The case is a standard 19” rack size 2U height, with nice diecast aluminium sideframe with integrated handles. For the case size, inside it is not very crowded.


 
The PCBs are double sided without solder mask but with silkscreen, there are three PCBs inside
- Power supply
- Timing board (clock generation, delay, trigger generation etc.)
- Output amplifier

The power supply is a combination of general LM78xx (compatible) regulators and LM723. The rectifier diodes are sitting in ceramic strips, and no, they did not buy these from Tektronix...



The Timing board consist of a nice mixture of components: soviet and hungarian TH resistors, SOT23 and TO92 transistors, variety of caps. Precision caps were sourced from EFCO in this unit. TH resistors mounted on both sides. The circuit layout is rather straightforward.





The frequency switch consist of 6 ceramic discs, the discs have gold plated contacts.


 
Delay switch and pulse width switch are mounted on the PCB while a cogwheel work translates the 90°angle between the front panel and the switch.


The output board follows basically the same layout as the timing board, the output transistors are BFR96. The timing board and output amplifier board is interconnected with thin coax cables ending with LEMO connectors, I have to emphasize here that in those days it was very-very hard to source those connectors.


 

 

 

[coromonadalix]

nice puppy    thks for the photos