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Old 23rd Nov 2022, 6:20 pm   #5
EnyaFox
Triode
 
Join Date: Mar 2022
Location: Reading, Berkshire, UK.
Posts: 48
Default Re: SPT Video RF Modulator

Quote:
Originally Posted by winston_1 View Post
SPT were in Malden in Essex and have been gone for around 20 years now.

I have a number of these modulators and a manual somewhere. They are high output vestigial sideband modulators to almost broadcast spec. The output is around 105dBµv. In your picture the left board is the power supply, the centre board is the actual modulator to BBC spec which gives an output at IF 38.9MHz vision. The module on the right is an upconverter to a (fixed) output channel. The digital display on the front panel is normally hard wired to display the output channel. Broadcast 2 to 12 and 21 to 69. Yours appears to show 88 which I think is cable channel S09. Be aware they may be setup with either a BG (5.5MHz) or I (6.0MHz) sound carrier.

Best way to test it is to connect it to an aerial input on a TV via around 30dB attenuator connect a video source and try to tune it in. Most modern TVs (except Panasonic) will tune cable frequencies, older ones may not.

Any more info required (including converting from BG to I) let me know.

Could it be a possibility that one or more of the resistors on the display have gone?

I think there is also something wrong with the power supply. I am trying to figure that one out but after a while of being powered, it would trip the RCD .
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