problem with silicon chip - FM micromitter

[Carl Ranson]

Hi all, thanks in advance for any help you can give.

Ive built the FM transmitter from the Dec2002 silicon chip mag.
As far as i know its all correct (im not a total beginner) but i can only
get 0.6v on the test point, instead of the 2v i should see.

Any suggestions what i should check?
CR

 

[Phil Allison]

"Carl Ranson" <carl.ranson@unify.co.nz

Hi all, thanks in advance for any help you can give.

Ive built the FM transmitter from the Dec2002 silicon chip mag.
As far as i know its all correct (im not a total beginner) but i can only
get 0.6v on the test point, instead of the 2v i should see.

Any suggestions what i should check?

** Your workmanship.

Solder bridges are very likely on that SM infested PCB, plus missed
joints, wrong way round parts.

VC1 is a suspect.



........... Phil

 

[Zebulon Blah]

On Wed, 17 Sep 2003 19:08:30 +1200, "Carl Ranson" <carl.ranson@unify.co.nz> wrote:

Hi all, thanks in advance for any help you can give.

Ive built the FM transmitter from the Dec2002 silicon chip mag.
As far as i know its all correct (im not a total beginner) but i can only
get 0.6v on the test point, instead of the 2v i should see.

Any suggestions what i should check?

I built not one but two of those FM transmitters from Silicon Chip
about ten years ago and I could never get either of them to work!

 

[Bill Bailley]

"Zebulon Blah" <wanker@myrealbox.com> wrote in message
news:1103_1063858009@Loud_Belch...

On Wed, 17 Sep 2003 19:08:30 +1200, "Carl Ranson"
carl.ranson@unify.co.nz> wrote:
Hi all, thanks in advance for any help you can give.

Ive built the FM transmitter from the Dec2002 silicon chip mag.
As far as i know its all correct (im not a total beginner) but i can
only
get 0.6v on the test point, instead of the 2v i should see.

Any suggestions what i should check?

I built two without real problems. I did notice with the second on that the

tuning seemed critical. In other words it went through the correct area VERY
quickly. All else being equal I put it down to the tuning core material
perhaps of a different batch. The cores are a mechanical problem (breaking)
which can be significantly improved like this.

Snip from previous post: - - - - - -

I will second the advice given above. VERY fragile. I actual broke two even
after following the printed advice to remove some of the rubber cemented
into a groove the length of the slug. My eventual fix was to remove ALL of
the rubber and use an inch or so of plumbers teflon tape wrapped around the
slug. Easy, smooth, and not so easy to break. Excellent kit by the way. I
have one on the rear of my TV so I can follow the sound better from a radio
on the side table, and one on the back of this box to send my OTR
collection to the shed, garden etc. (different freqs of course)

End Snip - - - - - - - - - -


Apart from checking everything obvious, take a x10 glass and look at each
and every pin on the IC. Look from both sides to be sure. Yes, I did that
and found nothing, but did in fact have an unsoldered pin. Use a digital ohm
meter to verify what your eyes tell you. Belt and braces troubleshooting is
well worth the effort on a small project.

Old Bill