Yesterday, I disassembled my Redsun RF1210 to find out if I could correct its sloppy tuning problem. I mentioned this issue in my redsun rf-1210 first look article.
The radio was easy to get apart. Here are observations and issues I encountered on the inside:
* There were several strands of dried glue coming off the circuit board.
* I confirmed that the tuning needle is not attached on the right side, which causes the annoying ticking noise when the radio is shaken.
* I couldn't figure out how to get the tuning faceplate off the circuit board, and that is where the problem likely exists, so I couldn't even diagnose it.
* It appears that removing the tuning faceplate would disconnect the tuning string, which would make things more difficult.
* The speaker did not have any markings to indicate wattage, ohms, or frequency response.
* During reassembly, the trickiest part was reattaching the band slider with its switch. I used a piece of plastic to push the switch all the way to the left, and from there it was easy.
I was disappointed that I couldn't poke at the tuning problem, because when the radio was back together, I rediscovered my fondness for the radio's speaker. I also got good results on shortwave frequencies when I clipped the RF1210's antenna to my DE31 active loop antenna. If the tuner was more reliable, I would use this radio more often.
Next, I decided to try its built-in battery charger even though I don't have any instructions for this radio. The power switch has an "off/charge" position, so I just plugged in the radio and turned it off. The charge light blinked faintly for a few hours. When the blinking stopped, I incorrectly decided to pull the plug and use the radio. In an email reply from Redsun that came later, they advised me to let the batteries charge for 12 hours.
When I measured the batteries with my multimeter, three of them were around the 0.8 volt level, and one was almost fully depleted. I decided to finish the recharging job with my external charger. Next time I have some depleted batteries, I will try charging them for 12 hours in the RF1210.