Radio Shack 2000629 Tech Page

A multi-band LW, AM, SW, FM, FM Stereo radio for $31? Who could resist! Even if performance isn't very good, it is still a good casual radio. Plus, I could really use a SW radio that can tune the frequencies I use when I design downhole drilling tools - to quickly sniff out transmitter activation and relative signal strength. I placed my order, and waited for the radio to ship to a local store.

The radio out of the box is as advertised. There are a lot of options on the radio - which leads me to believe it was originally a much more expensive radio. It does appear to be a re-branded Sangean ATS-505. But after many years of analyzing Radio Shack products, I am well aware of Radio Shack cost reduction design. A quick web search on the ATS-505 reveals that the Radio Shack is 2000629 is almost identical in appearance except for being black instead of silver. The operating instructions of the ATS-505 alse describe identical functionality. So the chances are good that this is a re-branding and not a re-design. Until I can examine an ATS-505, that will be my theory.

AM performance was lackluster - distant stations come in about as well as on an average low cost radio. FM selectivity and sensitivity is not bad out of the box, a pretty decent portable FM. Shortwave and longwiave appear to work properly and have a good degree of sensitivity. As I am not a big shortwave fan, I am not really equipped to comment on relative SW performance. However, the digital tuning, inclusion of all SW bands - the ability to tune off of SW bands and have general coverage is nice. I was disappointed that I cannot tune between the longwave and AM bands to have continuous coverage from 153 kHz to 30 MHz.

Like my other radio pages, this is a work in progress. I will start with the procedure to safely get to the circuitry inside.

1. Begin by removing the battery compartment cover and batteries, which are arranged in a group of three with a single battery underneath.
   
2. Next, rotate the antenna slightly up to reveal a short screw underneath. For longer screws are located in the circled locations.
   
   
   
3. As with other Radio Shack portables, the case is also securely attached by a series of tabs. It is really easy to damage the case by using a screwdriver to pry it open, so I like to find a place where I can start to pry without the damage being visible when I am done. Turning to the side of the radio:
   
4. It is easy to pry off the tuning knob and a clear plastic washer underneath:
   
5. This proves to be a very convenient place, and the case begins to separate easily:
   
6. The radio separates into two halves very easily:
   

   I recommend de-soldering the fragile speaker leads to avoid breaking them. The size of the speaker is a bit of a disappointment, but most people are probably buying this radio for shortwave, which seems to be mostly talk.
   
   

7. The back basically falls off. The whip antenna connection to the PC board is made through a pressure spring, so it doesn't have to be desoldered. Once the back is off, we can get our first view of the back of the PC board:
   

   There is one screw on the left hand side of the board, and several clips holding the board to the plastic chassis. I did not remove the board from the plastic chassis, though, because access to the top side of the board would prove to be very good even with the chassis attached. When you look at this PC board, you see numerous SOT-23 resistors and small surface mount passives. It will not be easy for the average user to work on this radio!
   
   

8. Now you can see the reason for the poor AM sensitivity - a relatively short ferrite bar antenna, which is also smaller in diameter than normal:
   

   Is it possible to upgrade this ferrite bar? It appears that the case is big enough for a 200 mm bar:

   

   Unfotunately appearances are deceiving. There is a "clarify" pot that is partially in the way. Also, you cannot use the existing AM and LW coils. They will not fit the larger diameter ferrite bar shown here. I had the good luck of having an extra longwave coil, and several extra AM coils.
   
   

9. To remove the existing ferrite bar, you start on the right hand side.
   
   
   
10. The ferrite bar can then be carefully pulled out of the left hand support. But be careful - there is some glue used to secure the bar, not just wax. You do NOT want to break the 8 wires coming from the antenna coils, because they are delicate and criss-cross in a non-intuitive fashion:
    

    I dd some experimentation, but didn't actually change out the antenna. To do that, I would have had to re-wind both the AM and LW coils - something I didn't want to do. I did take some close-ups of the connections in case you want to do it:

    
    
    
    
11. Getting back to my radio tear down, once the radio back and front have been separated, you get a good view of the display PC board:
    

    The display board is secured to the chassis by two screws and several clamps. But it is also secured on the side by a nut around the tuning pot and a clamp from a switch:

    
12. Once free of the chassis, rotate the board silightly to reveal a connector that needs to be unplugged:
    
    
    
13. The display board can then be flipped away, revealing a second connector that needs to be unplugged:
    

    This also gives us our first view of the top side of the circuit board. As I said - the access to the top of the board is really good. So I didn't think it necessary to remove the board from the chassis.
    
    

14. There are two ceramic filters for FM. This view shows them after I had already changed them out for 150's. The radio comes stock with 280's.