Hacker Sovereign III RP72MB Portable.
Having a soft spot for Roberts and Hackers, when this little lady came into the shop, I tossed away all money earning repairs and sat her on my lap.
She seemed to be dead. Applying 12v to the battery connections gave no results, but about 10 mA being drawn from the supply. A quick check over the amplifier PCB showed that with an injected signal, there was life at one end of the loudspeaker coupling capdensor, but nothing at the other end. It was open circuit. Thinking that was it, I replaced it and now the amplifier board worked but popped and cracked when moved. This board is connected by 2 plugs. They always fail, so snipped off and hardwired them. My expectation of joy and happiness was doomed. More testing showed that the headphone socket was duff, so hardwired that out. Then, found that the spade terminals on the loudspeaker were badly crimped.
I now had all sorts of pops and whistles, nothing seemed to changed when selecting different bands. I didn’t have a circuit to hand, so testing was all a bit shaky. A squirt of cleaning jollop on the pots and wave-change switches seemed to help. Injecting RF signals, FM and AM, to see what was happening started to give me some help, then, lots of crackles and the audio vanished at almost nothing. Loads of cold testing showed that a couple of blue Philips electrolytic capdensors were leaker, so they were changed. Now I had very low audio, but AM and FM seemed to be working.
These sets are so nice. The volume and treble, base controls are on a separate PCB. Good audio was getting to this board, but nothing coming out. There appears to be a buffer transistor in the tone circuit. Ah, another Philips decoupling capdensor was short circuit. With this replaced, we now had a fully working set. Sounding fantastic via the big loudspeaker. Loads of bass, sounding like a 1960 radiogram. Annoying and fiddly, but worth the end result.
It’s a shame that the FM only goes up to 101 Mhz which limits a certain amount of listening. Having said that, this part of the spectrum is allocated to music to mug by, so who cares.