Sky Digibox
Sky Analogue


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NOTE: This decoder is obsolete. Most accessories and modifications mentioned on this page are no longer available.

CTU916 Twin Card "Visiopass"

A few notes about these units.
They are ex rental imports from France hence cosmetic & electronic condition
can be poor-- the 2200uf capacitors (C2655 & 2650) in PSU are favourites for
patterning through to dead set.
Unfortunately the importers (fast buck cowboys!!) have ignored our requests
and omitted to to obtain service and user manuals!! Yes they would be in
French but we can overcome that.
Also it appears that there is a facility to programme these units to switch
themselves into standby after a predetermined time!! On going investigation.

As imported the these units have fully populated boards giving a PAL SVHS
output on rear panel but main output is SECAM from a secam coder on main
board. It is easy to change to PAL as there is a PAL coder on the MAC board
on MOST units--not all. (Non PALs tend to have 2 square sockets in line with
the audios on MAC board when viewed from rear).
There is an extra "AUX 2" scart on rear which can be used instead of "AUX 1
Magnetophone" but "Aux 2" has to be selected on remote control and set
reverts back to "Aux 1" on power up etc., so best not used. (Pin 20 takes
"MAC Baseband").

It is easy to convert the ones with PAL coder on Mac board: Locate R 3717
(150R) on main board component side (wire ended R), 75mm from left
side(viewed from front), 90mm back from front, in front of brown TDK filter
and cut left side leg. Extend cut end to pin 27 on header from MAC board.(As
viewed from front, pin 27 is the second pin back on right row-- if viewed
from "track side" there are empty pads where SMD R3093 & 3077 were fitted on
CTU 900).

Most of the mods for the CTU900 do apply to the twin card CTU916:

A. Flicker mod-- Change C2337 ). 0.47uF to 0.1uF. On MAC board.

B. Fit 56pF capacitor from C2341 -ve end to chassis ( suggest pin1 on TEA6420 ic 7402)

C. Remove VCR (magnetophone) scart pin 8 series resistor R 3062. Then link Tv and VCR scart pins 8 together. Now switching unit into standby will remove "pin 8's 12volts.

D. To make switching automatic on seeing a MAC signal: Do as in C. above. Then cut R 3083 (56K0) at end furthest away from scarts, and link R3083's cut end to R 3068 (68R) inboard end. If unit is 916 also fit 470R from this point to chassis--there is a convenient solder blob close by on the "ground plane",

The other mod to maintain CVBS on pin 19 of Tv scart is much more complicated on the 916 so I would give it a miss.

Regarding the 56R resistor in place of link 9202 -- don't do this unless you use a RDV/Torrid card., it prevents updating of multimac MM303 cards with remote control. These units are very fussy about which pic cards they will work with, and definitely will not auto switch between eurocrypt M & S or the card slots. Has to be done with remote control.

Adding PAL colour to the CTU916 with SECAM output

by Gerhard Oesterreicher


Everyone who would like to use the attached circuit should be extremely careful! Special care must be taken since the PSU can be touched, when the Visiopass is open. There is no additional shield against electric shock and there are some wires without isolation that carry harmful voltage. Even more care must be taken if you take the main board out of its mounting and view it from the solder side, AND have it connected to mains. So disconnect mains when you are inside there, unless you are adjusting something and need a running PSU.


It is a good idea always to have a look at the end of the mains cable automatically, before one puts his fingers into any equipment, to check that it is not plugged into an outlet.

Enough for life saving.

How to connect

The Input signals to the RGB to PAL encoder can be found under the decoder board on the component side of the main board.

These are:

RGB can be found at R3710(red), R3713(green) and R3708(blue), at their end closest to the scarts. The composite sync can be found at R3022 (2k2) at the end closest to the connector for the Decoder board.

A 12V connection must be taken as a supply. There is also a 12.5V supply point on the board, DO NOT TAKE THIS ONE!

I took the Ground from electrolytic capacitor 2872 (negative side, of course, nearest to the scarts) and the 12V from a bridge nearby. (I cannot read the label any more, it seems to be 9834.)

Take care not to bend the connector to the Decoder when taking the Decoder off or reassembling it. Read and follow the short text under the diagram! I killed 2 MC1377's by being careless with input signals!

Use a socket for the MC1377 and leave it empty while soldering your circuit (but don't forget to put it in afterwards!)

So, I hope this is of use for anyone and there are no people out there who had a business doing exactly what I describe. Anyway only persons with a little experience will be able to do this.


"RGB" and (composite) "sync" signals come from main board.
"PAL output" to be fed to TV, VCR or loop back to SAT receiver (a load of 75R is ok)

Before first time Power on:

Set all Pots and trimmer to middle position !


After supplying power and the four input signals, a TV connected to "PAL output" should at least show a black/white picture. If not, check everything again!
If a picture appears, adjust 30pF trimmer and sync level pot at pin1 to show a coloured picture. The 1k pot at pin9 allows to adjust signal strength.
Use 30pF trimmer, pot at pin1 and pot at pin9 to give the best visual results.

Change 10k pot at pin2 from middle position only if you cannot get a coloured picture by other means. Be careful with it, if the voltage at pin2 gets too high, the MC1377 could get damaged.

If there is sufficient interest, a kit of parts will be made available.


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