In message <35758B21.9281484F@btinternet.com>, fcembrola
<fcembrola@BTINTERNET.COM> writes
>Hello picsters!
>
>My project involves using a PIC 16C84 to
>control a UHF digitally programmable
>modulator. It uses the I2C BUS to program its
>modulated frequency.
>
>The modulator in question has 8 pins labelled
>as follows:
>
>1 - SCL (this is the serial clock)
>2 - SDA (the serial data)
>3 - VT
>4 - Video in
>5 - Audio in
>6 - +5v
>7 - GND
>8 - Boost
>
>I can understand, and know how to use all the
>functions of the pins except for
>pin 3 (VT). I have no idea what it is
>supposed to do and how to use it. I would
>appreciate any help or any hint where I can
>get the right info.
>
>The modulator part number is RMBT-UK36L

VT is the HT feed for the tuning voltage, it's usually 33 volts,
regulated using a 'super' zener such as a ZTX33B or a TAA550. I've just
checked the circuit of a Grundig GRD300 satellite receiver, this uses an
I2C modulator, this actually uses a 28 volt feed (which is also common
to the tuner), and is just a direct feed from the SMPSU, no extra
regulation at all.

BTW, did you manage to get a data sheet for the modulator, I've been
considering something similar, but don't seem to be able to locate data
sheets for the ones used in equipment that I've seen. I think most of
them seem to be made by either Alps or Mitsumi.
--

Nigel.

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