Post subject: Radio Shack Science Fair Kit- Need schematic
Posted: Mar Mon 12, 2012 5:55 pm
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Joined: Apr Wed 21, 2010 12:01 am Posts: 209
I managed to pick up an assembled Science Fair 8 transistor radio from a kit. Need to do some troubleshooting. The part number is 28-222. Does anyone have a manual or schematic for this radio? Ken
Post subject: Re: Radio Shack Science Fair Kit- Need schematic
Posted: Mar Tue 20, 2012 1:22 am
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Joined: Apr Wed 21, 2010 12:01 am Posts: 209
Wiscojim- Thank you! This is very helpful to me. Being an assembled kit already, the first obvious thing I got to do is check that the person assembled it right. By checking with the schematic, this will help tremendously. Once that is done, I can start troubleshooting, or maybe that's all that was needed and some parts were in the wrong spot or a wiring mistake. So far the only thing I found was a couple of poor solder joints and even some without solder. The radio is in good shape, cabinet is new, scratch free. I saw it in a box of several non working radios at a flea market. My guess the owner assembled it and when he couldn't get it working, just gave up on it and set it aside. I'll let you know how I make out with it. BTW, do you have one too? Thanks again. Ken
I found an uncompleted kit (all parts present) a while back. Looks like if they had completed it, it wouldn't have worked anyway. Very sloppy soldering!
Post subject: Re: Radio Shack Science Fair Kit- Need schematic
Posted: Mar Tue 20, 2012 12:34 pm
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Joined: Apr Wed 21, 2010 12:01 am Posts: 209
Wiscojim- I see what you mean. Good pictures. Mine is not too bad, only some poor solder joints. Yours is at a point where you can "rescue" and complete it the right way. Thanks again for the schematic. Ken
Post subject: Re: Radio Shack Science Fair Kit- Need schematic
Posted: Mar Tue 20, 2012 9:08 pm
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Joined: Jun Tue 21, 2011 8:27 pm Posts: 2064 Location: Virginia
Been wanting to buy the same kit for the past year now. Unfortunately, I keep getting outbid.
Anyway... would like to know the performance of this radio as it has a rather long ferrite antenna. Let us know when you get either of them up and singing!
Post subject: Re: Radio Shack Science Fair Kit- Need schematic
Posted: Mar Wed 21, 2012 2:25 pm
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Joined: Apr Wed 21, 2010 12:01 am Posts: 209
Success! After reviewing the schematic with the built board, there were no conflicts. So after touching up some solder joints, I got some background hiss. I then found the coils totally out of adjustment. After an alignment and resetting the antenna placement on the ferrite bar, it came to life. After a final alignment with a signal generator, it works fairly well. The sensitivity is good (not like a TRF) but pretty good. This kit was way out of alignment after it was built. This would be a big problem for a beginning kit builder with no signal generator. Ken
