UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Chinese 1A2 Super Regenerative FM radio kit

Philips210 · 30th Dec 2018, 5:05 pm

Hi.

I have made some progress with this kit and can report actually getting it to work after a fashion.
First off, the tuning cap as supplied needed its trimmers set to near minimum. As previously mentioned, there is an error on the PCB regarding connections to the tuning cap. The rest of the circuit was built as per the circuit diagram. The two 33uH RF chokes were replaced with some better ones that I had to hand.
The 100pF capacitor was changed for a silver mica type that I had available and fits the board without reshaping the leads.

On testing, all that I could get was a faint whistle and little else.
I changed the 1A2 valve for a new Pinnacle DK91 and it started to work. The setting of the 20k pot is critical as it starts to oscillate if advanced too far and could cause a nuisance to other radio users as the super regen circuit behaves like a transmitter. The tuning cap adjustment is also quite critical and hand capacitance effects are a problem. The audio is somewhat distorted but at least the circuit can work so I'm pleased that I have got this far.

Regards
Symon.

30th Dec 2018, 5:05 pm	#71
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Chinese 1A2 Super Regenerative FM radio kit Hi. I have made some progress with this kit and can report actually getting it to work after a fashion. First off, the tuning cap as supplied needed its trimmers set to near minimum. As previously mentioned, there is an error on the PCB regarding connections to the tuning cap. The rest of the circuit was built as per the circuit diagram. The two 33uH RF chokes were replaced with some better ones that I had to hand. The 100pF capacitor was changed for a silver mica type that I had available and fits the board without reshaping the leads. On testing, all that I could get was a faint whistle and little else. I changed the 1A2 valve for a new Pinnacle DK91 and it started to work. The setting of the 20k pot is critical as it starts to oscillate if advanced too far and could cause a nuisance to other radio users as the super regen circuit behaves like a transmitter. The tuning cap adjustment is also quite critical and hand capacitance effects are a problem. The audio is somewhat distorted but at least the circuit can work so I'm pleased that I have got this far. Regards Symon.