Sinclair MTV1 service manual V2.1 Page 13 of 39
Circ
uit diagram for reference only; it is suggested you refer to the original later in this document.
Video IF Amplifier
IF amplification, after the tuners, is carried out in two stages, on a Sinclair designed bipolar linear
Integrated Circuit (IC). IF frequency response is determined by tuned circuits. Unwanted responses
are rejected by traps. AGC is applied to both IF stages.
The varicap diode voltage regulator and tuner AGC delay circuit are included on the video IF
amplifier IC.
The two ICs mentioned were made by Texas Instruments and are now completely Unobtanium. No
data sheets appear available and there is no obvious substitute. A dead IF panel IC essentially
means the rest of the set becomes a parts donor. Thankfully though, these seem to be reasonably
reliable and not subject to too much stress in their application.
Video Detector
This is a low level synchronous (switching) detector, providing both positive and negative video
outputs at low impedance. The circuitry is contained in a Sinclair designed bipolar linear integrated
circuit which also provides APC, gated AGC (for high noise immunity) and composite
synchronization pulse outputs.
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