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Bang & Olufsen Beomaster 3000-2 receiver. A wonder of aesthetics, winner of the "IF Award" in 1972, designed by Jacob Jensen, and a model featured in the Museum of Modern Art in New York.
I purchased this unit as functional... somewhat.
It had many issues, and some are still not fully resolved, but I don’t want to take any more risks with it. First of all, the audio amplification was completely off. Someone before me had attempted to replace the output transistors on one channel and then probably gave up. After much struggle and more swearing (being a compact construction, everything is crammed in), I disassembled it and measured all the output transistors-they were fine. Four wasted hours of my life. Then I checked the drivers. I compared the two channels, checked the diodes, resistors, and electrolytic capacitors-all replaced (including the tantalum ones). In the end, the issue was a troublesome BC242 way before the outputs. After that, the horrible channel returned to a somewhat normal state. I say "somewhat" because, surprise, a couple of power resistors on the power side were also out of spec. I adjusted the idle current; everything was okay, and the heatsink was just warm during normal operation... normal but not quite, because about six months later, I discovered that the audio amplifier developed another issue-transistor noise. It’s hard to describe, manifesting as a sort of crackling/rain, with volume fluctuating up and down, regardless of the volume and tone adjustments on the potentiometers. Anyone who has encountered this will recognize it immediately. Having dealt with similar issues in other amplifiers, I began my investigation quite confidently. I quickly found the culprit-a BC184 in the preamp, after the tone corrections. It measured with a beta/hfe of 10, plus a diode in parallel with it... I replaced it with a BC547 and then also swapped its neighbor, a BC149, which was still okay but a bit suspect, as a precaution. Although only one channel was affected by this problem, for the sake of symmetry, I replaced both transistors there as well. Everything returned to normal after that; the background noise disappeared.
The other MAJOR issue with it, and the reason I do NOT recommend anyone buy similar Bang & Olufsen products from that era- the keys, ALL of them, are terrible. The contacts are oxidized, but to access them properly, you need to disassemble almost the entire receiver. Given how cramped it is, I’m really afraid I won’t be able to put it back together correctly. It would have been somewhat feasible if the damned keyboard hadn’t been glued to a plastic sheet with copper traces on it. It’s the first time I’ve seen such a mess in a product that claims to be of quality. It feels like a slap in the face to anyone trying to repair it. If I wanted to peel off the keyboard, I risk melting the damned plastic where the copper traces are... pff... so it’s better to leave it. I flooded the whole keyboard with contact spray; the situation improved a bit, at least now the receiver executes all functions. However, the keys are still difficult to press and noisy... giving the feeling of “it’s going to break” with every press.
The markings on the sliding scale and the potentiometer buttons were worn off, so I repainted them as best I could. I also tried to clean and reduce the yellowing of the transparent plastic parts; I left them for a whole day with hydrogen peroxide, exposed to the sun... but to no avail. Oh well, that’s life. Most of them on the internet are unfortunately yellowed.
I've also put some woodgrain sticker over the original wood veneer case which was badly scratched.
Another issue-the transformer-is placed in a metal box, encased in epoxy resin, but after heating up, it starts to hum after about 20 minutes. Annoying, as it could be heard even with the casing on the receiver. I have about 30 receivers from the 60s to 80s, and none of them have a noisy transformer, except for this one. And no, it’s not just my unit; the entire internet complains about the transformer in this model.I put a lot of hot glue around the transformer; now it’s somewhat acceptable, and it’s possible to listen to music on it without the buzzing at 50 hertz.
As for FM, I extended it to 108 quite easily, changed the Zener diode for the varicap voltage, and then adjusted the voltages. As a radio, it works properly with good sensitivity. The audio amplifier is also good to excellent (very good tone corrections) nothing to complain about... once repaired.
For devices from that period, I recommend staying away from this model and instead getting something solid and durable from Grundig, Braun, Nordmende, Telefunken, Saba, or Blaupunkt. All of them are far superior in terms of ease of repair, and most of their Hi-Fi products are at least equal in performance, some even surpassing the Beomaster.