This one is a 139 tube SW receiver I purchased from eBay. The previous owner could never get it working,
and I was pretty confidence that I could get it fixed since I have all the spare
tubes, parts and manual. The reason I
want to have it is that it has Chairman Mao’s quotation on it, it is a highly sought-after item in China. It would normally sell around 3000 Yuan (about $450).
After received it, I connected the power and turned it on,
no sound at all. It was expected. I opened it up, the first thing popped into my
eyes was the fuse. I took it off and
found the wire inside was broken. I
found a spare fuse, put it on, turned on the receiver again, sound immediately
came out from my headset. I was
pleased. This receiver was made in 1968,
and it has been 50 years since.
One question I have on this receiver is that it is all-tube radio,
I expect a delay after turn the power on since it takes time to heat up the
filament inside tubes. But this receiver
does not have any delay once the power is turned on. why is that?
(The standard power source for this radio is a 1.5V / 90V unit battery. The one I use is a DIY power convertor I brought in China many years ago.)
Posts
"One question I have on this receiver is that it is all-tube radio, I expect a delay after turn the power on since it takes time to heat up the filament inside tubes. But this receiver does not have any delay once the power is turned on. why is that?"
ReplyDeleteI have one of these receivers. When I first fired mine up, I waited for the tubes to glow. And waited, and waited... Anyway, I put on the headphones, and it was working great! The tubes employed are small and low power and use the filaments as cathodes, so they start emitting electrons almost immediately. This type of tube was common in battery-powered tube radios.