Always like it when you get something in to repair that is a nice piece of kit and the owner appreciates what he or she has. Am I allowed to use gender these days? We have a lovely Hacker RP18 portable radio. Have had several Hackers in over the last few weeks. Mrs Hacker gave birth to this chap in 1965 and was one of the early adopters of VHF-FM. If you wanted to buy one, it would have set you back a week’s wages.
Popped him on the bench and fed him with 18V from the bench supply. Normally you get a good crackle when you switch on and if you are lucky, some stations. Ummm. Absolutely nothing, nada, zip. Speaker connections were okay and power was getting to the amplifier board. After a bit of poking around with the ‘scope there was no audio input from the RF sections. Inject a signal, but still nothing. Looked at the electrolytic capdensor which couples the speaker to the push pull amplifier stage. Total open circuit, robbing the speaker of any musical pixies. Replacing that and fixing the bias slider pot, the amp was working.
Still nothing around the RF sections. In these sets, the VHF and AM sections are quite separate so as we had nothing from either, we were looking at 2 or more faults. Starting with the AM section, the DC conditions around the RF amp and detector stages were off, but we did have a local oscillator running, leading me to glare at the AF115 transistors. As per usual, a snip at the screen leads and now we had LW and MW working well.
The VHF section, I feared was going to be a bit more painful. Hoping the faults were not going to be in the VHF module, a signal at the I.F. frequency was injected, which could vanished at one of the AF114 transistors. Thinking my leg snipping would work wonders again was short lived. I had to actually change one of them. Shock horror. With that done, VHF worked really well.
These sets are so well made and must have been very man-hour intensive. But the end result speaks for itself. Audio quality is fantastic, bass and treble controls and a Goodmans speaker the size of a dinner plate.