G11 Remote Control

Rich (Marconi_MPT4) has supplied some photos and a description of the G11 Remote Control:

G11 ULTRASONIC REMOTE DESCRIPTION

Description

The Philips G11 ultrasonic remote control transmitter utilises an SAA1124 multiplexed keypad encoder device at the core of operation. Each function button is assigned a unique frequency derived from a 4.433619MHz crystal oscillator integral to the encoder IC. The frequencies produced are as follows:

STANDBY 33.96kHz
RESET   35.00kHz
MUTE    34.30kHz
BRI +   34.65kHz
BRI –   35.34kHz

COL +   36.04kHz
COL –   36.73kHz

VOL +   37.42kHz
VOL –   38.11kHz

(Row 1)                       (Row 2)
BBC1    44.00kHz         BBC1    42.96kHz
ITV     43.66kHz             ITV     42.62kHz
BBC2    43.31kHz          VCR     42.27kHz

G11 RC

When a button is pressed, the corresponding generated frequency on pin 15 of the SAA1124 is directly coupled via a resistor network to TR1 BC548 and transformer T1 in order to step up the transducer drive signal to roughly 140v pk-pk. This signal is also rectified to produce a bias voltage of 80 to 90 volts for the transducer via a 10Mohm resistor.

A standard 9v PP3 battery is fitted and current consumption measures at approximately 16mA when remote is operated but can vary by a few milliamps depending on the button pressed. Standby current is in the order of microamps.

Two additional versions of this remote were produced with a full complement of buttons for Teletext and Viewdata receivers.

Faults

Membrane keypads either go permanently short resulting in a flat battery after two days or just fail to operate. Often the latter fault is caused by the flexible membrane between the connector and keypad cracking or splitting. The black buttons regularly break off due to the use of very thin plastic webs. During the maintenance period, Philips provided upgraded parts to effect a more reliable repair.

Another very common failure is the transducer stops working due to the remote being dropped or contamination getting in through the front aperture. Occasionally the drive transformer fails with open circuit windings through contamination. Orange juice is lethal!

I should add that pets absolutely hate these remote controls, sends them mad, and on many occasions a German Shepherd or two has sunk its teeth into the controls piercing through the top membrane, PCB and case.

Rich (Marconi_MPT4)

 

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