FM Wireless Transmitter

[Bigears]

Hi just wondering if anyone has purchased a FM Wireless Transmitter DIY Kit TFM009 FM Radio DC 1.5V-9.0V on ebay, although I am just a beginner, this kit came with just the circuit board and components and no diagram or instructions. Has anyone got any information on this that would help.
It's the small Caps the Mic and the Transistors I am worried about.
Regards Ken

[Boater Sam]

Its all conventional components, no surface mount, so a miniature iron and a good fast soldering technique should see you OK.
Get some soldering practice first with scrap bits on an old pcb?

[Techman]

Originally Posted by Bigears

this kit came with just the circuit board and components and no diagram or instructions. Has anyone got any information on this that would help.

I've just looked this up and all the instructions with circuit diagram, component list and values are all on the sellers advert, so no need to add a load of unnecessary paperwork which would mean that it would no longer qualify for the free postage. Just save the images and print it all off.

[Bigears]

OK Techman thanks for that

[Bigears]

ut the small caps are all different values with no indication where they should go, also how do you tell which is negative or positive on the small Mic and no real instructions.

[Steve G4WCS]

theres a parts listing giving component numbers and values and the PCB is silk screened with the component idents

[ms660]

The mic connection pins are offset, just fit to line up with the mic footprint that's printed on the board.

Lawrence.

[Bigears]

Ok thanks Steve

[Bigears]

OK thanks Lawrence

[Al (astral highway)]

Originally Posted by Bigears

ut the small caps are all different values with no indication where they should go....

Hello, the caps all appear from your photo to be small ceramics. They will have a number on them, like 102, 103, 104...

Look these up on a commonly available (online) chart of capacitor standard values, expressed as picofarads, nanofarads and fractions of a microfarad . For example ... https://synthrotek.com/wp-content/up...itor-Codes.pdfThey translate into a value: most will be between less than 100pF and 100nF (0.1uF) They can go in either way.

I can’t spot any electrolytics from the photo, there should be at least one small radial one (leads come out at one end ) however, of about 33-100uF, for decoupling the power supply (a battery?) if so it may have the -ve marked with a black line or bar.

Be methodical: perhaps start with the jack, mic and variable resistors , then the fixed value resistors , then the capacitors, then the inductors ( the coils ) then the transistors, being careful of orientation.

Remember, you’ll need to account for the board being upside-down when you’re soldering so double check your transistor orientation and maybe hold them in place with some tape before you make the soldered joint .

[Bigears]

Thanks a lot Al, I asked the Guy who sold me the kit and he sent what I was looking for.

The only problem is the mic, on the SB looks fine, but on the mic the two wire are centred, not "off centre" so it's hard to tell which is - or +
I will Crack on and see how it goes.

regards Ken

[SiriusHardware]

If you look at the underside of the microphone, one of the leads will be connected to the overall metal body of the microphone by several fine tracks. That lead is your 0V, the other lead is 'signal'. If you are handy with a meter, you can also do this check with your meter on continuity or a low ohms range - whichever of the two leads is connected directly to the microphone body is the ground / 0V side and the other is '+' or signal.

[tri-comp]

You may be able to identify the negative terminal if your Conderser Mic. Capsule looks similar to the one in the picture attached.
As the Microphone most likely has an active amplifying element (FET-Transistor) inside it's important to attach it correctly to the power-supply.

[Bigears]

Thank you , Nonodeby Nonode and Heptode

I did notice two small greenish leads on the underside connecting to the body,but I did know the significance of them, I need to take it back off and check it. I will note this info in my notebook.

Regards Ken