Andrew Dickens wrote:
Hi. We have a stereo (two channel) Marti STL-10 system.

A few weeks ago we started noticing noise, and we traced it to the STL link.
One of our two STL transmitters was showing a low +13.5 voltage. We
discovered this voltage was +13.5 when not transmitting and dropped to +9v
when transmitting. We pulled the unit and swapped out the power supply and
the symptoms disappeared.

So, you checked the positive regulator?

BUT - while that unit was out we ran with our supposed good unit (normal
meter readings). All of a sudden we started hearing significant noise on
that channel.

What sort of noise? Crackling? Hissing? Humming?

Is there ripple on the power supply output? If you swapped it with a power
supply that has been sitting on the shelf for years, I could see why a cap
might fail and produce a lot of hum.

Anyone have experience with noisy Marti units? Where should I search first?
Transmitter or receiver? Noise sounds like HF clipping - all kind of
distorted in the high end, almost like an echo on a long distance line.
Unit is using 75usec pre emphasis and driven below 100% modulation.

HF clipping doesn't sound like noise. Are you talking about a noise problem
or a distortion problem?

A line echo does not sound like either noise or distortion.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."