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Micomitter kit.

Hello all, I have recently decided try my hand at some electronics project. My intention is to built a few kits so as to learn a little more about things and maybe gain some useful knowledge.

That said, I decide to try my first kit and bought a micromitter (FM transmitter) kit from Jaycar. I like to do a bit of work around my yard and have over 40GB of mp3 music on my computer, so I figure that it would be quite a useful item as well as a helpful learning tool.

I started by thoroughly reading the manual and a kit builders starter guide. After identifying and sorting the various parts I set about putting the kit together. Following the instructions, I firstly tinned of the legs of the IC and soldered it to the board. Checking the connections for continuity, I found I need to touch up 5 out of 22 and checking again after found a good result.

I then set about soldering in the remaining components and checked each join under a magnifying glass, touching up as required and double checking the position.

Testing went as follows:

Test 1. Apply power and turn switch on. Result; No puffs of smoke, frying sounds or heat (Phew!)

Test 2. With unit powered up, test voltage from ground to leg 8 on the IC (result should be around 5V). Result; 4.97V (Yay!)

Test 3 (& adjust). Measure across test points to tune oscillator, adjust to

2V. Result; 0.6V and I cannot change reading in any way, even removing the ferrite plug made no difference. (buggar!)

So have I done wrong?? Is anyone familiar with this kit? I am thinking of de-soldering the copper wire coils from the former to check and re-solder. I will also re-check the layout just in case I have put something in the wrong place.

Any clues??

Your help is greatly appreciated.

Thank you Noel.

PS. Does anyone know if such a thing as amateur electronics clubs (should this animal still exist) around the northside of Brisbane.

Reply to
Noel
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Don't know about that kit, so can't help out there, sorry, but if you are into RF transmitters then check out the (old) Talking Electronics bugging books. An excellent way to learn electronics, and build some useful and fun kits too.

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And it looks like they still sell all the kits too.

Dave.

Reply to
David L. Jones

Schematic?

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Reply to
Hugh

Presumably this is it:

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Full article here:

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Dave.

Reply to
David L. Jones

Noel,

I had the same problem when I bulit it but worked it out. The tank cct does not have sufficient range in combination with the PLL control voltage. See the following link where I explain this as Geoff C.

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Reply to
geoffjunkster

I thank everyone for their input but...

No luck with any of those comments I am afraid.

The link to the scematic was an obsolete model but similar enough to what I have except the bandpass filter and a jump pin / link for high & low freq range.

I can not get passed 0.6V on any freq setting.

Contacting the supplier gave this result:

"Below are suggestions from the designer:"

"The coil must be wound exactly as shown in the photographs with the direction shown and with it close to the PC board. The wire ends must also be scraped of the insulation so they can be soldered correctly"

I de-soldered the copper wire, that took quite a bit even with the solder-sucker so I suspect the join ('s) may not have been the issue.

As the former I am using is the type with the base to be soldered in, I left it where it was, re-installed the copper wire and tested again. Still the same result.

So I once again de-soldered the copper wire, then also the former. Inspecting the former, I found several lugs on the former which would (and did) hold the wire up further away from the board. I filed off these lugs and re-wound the wire ensuring it all sat down as close to the board as possible. Still the same result when testing.

I then decided to try some audio input and found that it works. Unfortunatly it is not a strong signal and the receiver is not indicating stereo (would that be because of the low volatge through TP1?) but it is working. I just need to grt it up to full power to make it usable.

Reply to
Noel

See this forum,

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Reply to
geoffjunkster

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