Two years ago, my father and I both received a Tecsun PL-660 radio as a Christmas gift. We both have had good experiences with our radios and generally enjoyed them until they recently both stopped working. I should mention my radio has been at my house in Arizona for the last 2 years, while my Dad's radio has been in Pennsylvania. So they have been in completely different/isolated environments.
My Dad's radio died first and seemed to be completely bricked. There was no on-screen display at all, and no combination of batteries or wall warts was going to get that radio to do anything. It was a doorstop.
About a month later, my radio starting flashing the display and blinking a "Lo battery" message. Changing the batteries and/or using the wall adapter did not improve the situation at all. The radio simply will not turn on.
Now, some cursory googling has shown a lot of people have had problems with this model of radio, and for the price they generally give up and get a new one. However, we generally take good care of our gear and the radios were gifts so we decided to see if we could do anything...
After taking apart my Dad's radio, I noticed there is a small button battery welded to the main board. Reading the battery in place showed it to be completely flat. So we did some surgery and 'popped' the battery off the board. We did some guessing as to the correct voltage, but putting 4.5v from an external set of AA's was enough to bring my Dad's previously dead radio back to life. Almost.
The display (computer?) has come back to life, we can turn on the radio and selecting different bands works. The radio will tune and looks like it should be working. However, we still have NO audio at the speaker or the headphone jack. The on-screen signal strength meter is completely flat, and the internal display 'backlight' will not illuminate.
I could theorize we had two separate issues, and we only fixed one of them by repairing the flat battery - or maybe we flexed/broke something when removing the original button battery from the board.
So the crux of my question is for some input of what else we might check? I don't have access to the second radio at the moment, so there is no way to find out if the battery repair is enough to bring the second radio back to life. Until I can do that test, I figure we can continue to tinker with the radio we do have. But what should we chase? Obviously we aren't going to get into replacing surface mount IC's etc. So I'm fishing. Any ideas?
I have not pursued trying to fix this radio any further than I described in my original post. However, I did do some research on the net and found some additional resources I thought might aid anyone else trying to repair their radio.
First, I found this blog post regarding ESD repair to a Tecsun 600, which might be similar in design to the 660:
I was also able to locate schematics for the PL-600 and PL-660 radios - both printed in (what I am guessing is) Chinese. I no longer can locate the URLs for those, but they can hopefully be found with some Googling...
Finally, I remember reading someplace that there is a 3.5v (I think?) voltage regulator on the radio mainboard, that frequently goes bad. I think it was a surface mount component, and that is beyond my skill level to replace - so I never pursued it further. I've never even looked for the component to see if I could locate it. I'm mainly mentioning it because there was renewed interest in my original question, and if someone does manage to repair their radio, it would be interesting to know if that is indeed the culprit or if it's something completely different going on.
I still have hope of eventually fixing these radios, but it is far down on my list of projects.