Pace SS9000/9200 decoder reset mod.

The SS series decoder is very slow to lock-in when you change channels, sometimes taking more than 10 seconds. The reason for this is that the decoder takes time to decide that the previous videocrypt signal has disappeared, then it has to try and find the new one. The later Pace receivers (PRD onwards) are far quicker, this is because they reset the decoder when you change channels, so it can start looking for the new signal straight away.

The SS receivers can be modified quite easily to reset the decoder on channel change, there is a line to the decoder SCART socket intended to reset an external decoder, and this can be used to reset the internal decoder as well.

If you have an SS9200 make sure the decoder settings in the tuning menu are set to INT decoder, not AUTO - this will save a few seconds when you change channels, as the receiver otherwise looks for an external decoder everytime you change channel.

The modification consists of an NPN transistor (BC107 etc.), a 4K7 resistor, and a 0.33uF capacitor.

1. Remove C31 (10uF near the rear between two 40 pin chips) from the decoder PCB, and replace it with the 0.33uF capacitor - this shortens the time constant of the decoder reset circuit. I fitted the capacitor on the underside of the PCB.
2. Fit the transistor across the capacitor, emitter to ground, and collector to the old positive connection of C31. Leave the base lead sticking out, I fitted the transistor on the top side of the PCB with the base lead pointing over the 40 pin chip towards the PSU.
3. Solder the 4K7 resistor to the base lead and run a wire from the other end down to IC U10 pin 5 (a 74LS16). The resistor can be glued to the top of the 40 pin chip, this will keep everything nice and tidy.
4. That's it, the decoder should now lock-in far faster, just like the later Pace receivers, it makes the SS series MUCH! nicer to use.

Thanks to Dave Plumb dplumb@cix.co.uk for sending me these details.

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