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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 17th May 2019, 9:15 am   #1
'LIVEWIRE?'
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Exclamation Quiescent Current of a Yacht Boy 300 Radio

Having just replaced a partially s/c transistor (T4) in one of the above, the radio now works fine, and, measuring the current when the set is powered from a stabilised PSU set to 7.5v, the minimum, with volume at zero is 20mA, and the maximum about 250mA with the o/p on speech peaking at around 1.4 watts into 4 ohms. Having mislaid my Yacht Boy 300 service sheets, I'm not sure if these are acceptable figures, so, can anyone tell me what the quiescent Current should be. The radio is only ever run from a 'wall-wart', but over the years the audio amplifier has failed twice. The last time I replaced all the transistors in the audio amp. with the types originally used, and, IIRC, one of the electrolytics, so I want to ensure, as far as possible that it's not likely to fail again.
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Old 17th May 2019, 10:11 am   #2
simpsons
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Default Re: Quiescent Current of a Yacht Boy 300 Radio

Attached is the schematic which whilst it doesn't show current, the expected voltages are shown. Hope this helps.
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Old 17th May 2019, 10:26 am   #3
paulsherwin
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Default Re: Quiescent Current of a Yacht Boy 300 Radio

20mA quiescent sounds plausible for this sort of design, though I don't have the actual figure.
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Old 17th May 2019, 10:59 am   #4
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Default Re: Quiescent Current of a Yacht Boy 300 Radio

Thanks, simpsons & Paul for your replies. There is a pre-set pot. on the PCB, but I may leave well alone as the radio works OK as it is. I don't recall from where I got the yacht Boy 200 & 300 diagrams. Those models aren't in the 'Instant Downloads' list.
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