rim: DIY: Signal tracer according to Radio RIM schema

as a pupil I "devoured" the Heinz Richter books in which many schematics of Radio RIM¹ kits were discussed among other things. I was fascinated of e.g. the "signal tracer", probably because of the strange term and the two figures shown in the book which I added on the equipment sheet.
I could not afford or did not want to buy the kit, could also be that it was not offered any longer at the beginning of the seventies (of the last century). However, I had already collected many component parts during my life as hobbyist, and now I got a cannibalized casing and the power and the output transformer from a small EMUD reverberation amplifier. This should be sufficient to build such a signal tracer with parts of my own, I thought for me and started the realization.
"Printed circuit boards" (PCBs) were a MUST HAVE at that time if you did not want to be classified old fashioned by the "dear" colleagues who only worked with solid states / semiconductors and did not understand my "tube maniac" behaviour. A little bit more self-confidence or with today's state of experience one would qualify such approach as nonsense: Laying-out the board, exposing to light, chemical etching, washing, drilling the holes, such a lot of work for only one single apparatus!
The casing was provided with a new front panel made of aluminium. After drilling it was labelled with rub-on-letters ("Letraset") and sealed with "Plastic spray 70". The front panel also serves as a "rack" (chassis) for the component parts including the PCB and with the exception of the transformers and the loudspeaker.
For this part half a million of small holes were drilled into the rear side of the casing. After that they were covered by a special type of cloth. I changed the original design regarding the tube equipment, instead of ECL 82 the "more modern" ECL 86 was used . And my apparatus was not provided with the optical indicator tube EM 80 (magic eye) because this was not necessary in my opinion.
In 1978 an important change was carried out. The PCB-part with the first and second amplifier stage (ECC 83) was cutted and replaced by a sticked-on new two-layer PCB. The top layer serves as an additional screen. I cannot remember exactly why but I guess because of radiated mains hum from the power transformer.



Today, the performance seems still very well, but for a satisfying sound it is necessary to use an external, proper speaker. The built-in one sounds "metallic" and acts as a makeshift.