elukam wrote: By replacing the resistor with a smaller one, you also destroyed the concept.
Actually, I hadn't thought of that; I destroyed the concept, for which I should be serving a life sentence
However, because I knew the concept I was able to destroy it; after analysing the schematic to find the cause of the problem and remove it easily.
I would add that the M531S has a large overdrive margin. The only trouble with this tape recorder is/was the short (40 mm) potentiometers in the adjustment of all parameters, so also the recording.
In the case I described there was an impact of the long connection cable, so I should either recommend the use of a 0.5m cable or the use of suitable DI-Boxes (read what these are), but in "those days" we only used them in sound systems (bought for foreign exchange)
Home appliances were simply "upgraded" on a massive scale on their own, for example: replacing universal heads with ALPS heads, phono cartridges with Shure, amplifiers in Radmor by replacing the power amplifier board with TIM-less ones (a company from Gdansk or Gdynia sold these amplifiers, but mainly Secam-Pal transcoders).
This was not an aldiowódó, it was replacing what the manufacturer could not use because, for example, the 'foreign exchange input' exceeded the permissible limits.
On the subject of gilding;
gold plating of the feet in Polish BCAPs (used e.g. in industrial automation modules, telephony) was still in use, although plastic technology and whitened feet of everything was already coming from the West. This cheapened their production "a thousandfold", and thus the price of the equipment. Continuous miniaturisation entailed the large-scale integration of integrated circuits, and thus the digitisation of everything, which was fashionable, so that completely new gadgets, unthinkable a dozen years earlier, could be put on the market.
Gold is still there where you can't get rid of it; on the pins of processors, expansion cards, modules.
Oh, and on the contacts of the fuses in the aldiode.
