MK118 FM Radio Kit- no sound?

I just completed the FM radio kit and can’t seem to get anything from the speaker. I believe I’ve assembled it correctly. I suspect the two wires I used to connect the speaker- perhaps they are too thick a gauge? When i turn it on, the LED lights, but there’s absolutely no sound- I’ve connected it to a 12V DC power supply that has a 300mA maximum rating. . .

Check your assembly, every step is important.
Try to determine if the problem is situated in the receiver part or in the amplifier part. Remove IC1 from its socket and touch any lead of R9. You should hear a loud hum from the speaker (turn up volume). If not, problem is in amplifier part (check all components around IC2.
If the humming noise is present, examine receiver part. Make sure all legs of FM front-end are soldered. Have a friend take a look at your circuit.

I removed IC1 and touched both leads of R9 and did not hear a hum from the speaker, so I suspect the amplifier circuit. All other componenets have been correctly installed and soldered (with proper polarity). I might get a new LM 386N chip to see if that is the problem. After installing the chips in the sockets, I added some additional solder to one leg of the LM 386N socket- I’m not sure if these are extremely heat sensitive, but that may have killed the chip? Also, I am using a 12V DC 300mA power supply, but the kit calls for a 12V DC 100mA power supply- would this matter?

A defective IC is unlikely but possible.
I’m sorry, but the nature of your questions gives me the impression that you are a novice, which is fine, but slightly enhances the possibility that an assembly error or soldering error is causing this problem. It might be wise to ask for local help in order to check out your project.
The power supply is fine.

I purchased a new LM386N-1 chip (IC2) from Maplin for about £1.28, and that solved the problem! I turned the radio on, the speaker popped and static came through. I pulled up the specs for the LM386N chip online, and the maximum solder temperature for the chip is 500 degrees Farenheit for 10 seconds- when I went to re-solder the IC socket (with the chip still in it) my solder station was set at 550 degrees Farenheit. I probably fried the chip by using too high a soldering temperature. I should have removed the chip from the socket, but I was being lazy. . . I’ve been repairing solid-state pinball games for about 6 years, and my soldering technique is pretty good. I think these kits are great for perfecting technique and learning more about electronics. I just need to work on my patience and remove the chip the next time the socket needs to be re-soldered :wink:

I forgot to say thank-you for your assistance- thanks so much!


ive had the same problem, where theres no sound to the circuit board, but when u turn the circuit board on there is a little boom but then doesnt work again, ive tried what you said to the other person but the nothing happened, is there anything else i can do or is it the same thing with the chip?

If you do not hear any hum when performing the tests mention above, there is definitely a problem in the amp part of the circuit. Check if the IC receives the supply voltage. Check all parts surrounding the IC for orientation, values and soldering. Also check continuity of tracks and solder pads between these parts. If any doubt, replace the IC.