Quote:
Originally Posted by wa2ise
I remember those hot chassis SS sets, usually a hogh voltage audio output stage, with an output transformer quite similar (if not the same, usually smaller) to those in tube sets. The rest of the set ran on the more usual 10V or so found in transistor radios.
 typical schematic.
GE used to get that by using the output audio transistor's emitter. They biased this transistor so it would yield about the before mentioned 10V, after the emitter follower audio was filtered out. Mostly an emitter resistor bypass cap. Other designs just dropped the high voltage B+ thru a power resistor to get the 10V, along with some additional filtering caps. I'd estimate that these sets were made from around 1965 to 1973 or so, then digital clock radios came out that used small power transformers for the clock circuit, and might as well use that to run the radio part as well. By then, it all came from Asia...  |
I remember seeing a small GE red LED clock radio with a transformerless "hot chassis" power supply. I know this radio wasn't older than the '80's and it could have been from the early '90's. I was shocked to see such a new radio using this type of power supply. The early '70's Zenith Korean set I mentioned also has this type of power supply.