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|FRAME NO. 5—THE OPTICAL UNIT.|
The body of the optical unit is a light-alloy casting in which the spherical mirror 1, plane mirror 2 and corrector lens 3 are permanently fitted. These are accurately aligned at the factory and need no further adjustment. The cathode ray tube mounting, deflector coils and focus coil, are attached to yoke 4. This is held in its pre-set adjustment against spring pressure. Mechanical adjustment of the focus coil for centring the raster on the tube face, and of the position of the cathode ray tube with respect to the spherical mirror for focusing is provided, and the method of adjustment is decribed in detail later. Full instructions for fitting or replacing the cathode ray tube, and for fitting a new focus coil or new deflector coils, is usually given in the service manual issued by the set-maker. It is therefore not necessary to describe these operations in detail, but the next few pictures indicate that it is quite a simple matter.
|FRAME NO. 6—FRONT END OF OPTICAL UNIT.|
On the left is shown the front view of the unit - the cathode ray tube has
been removed for clarity. The locking plate 5 (if fitted) prevents movement
of the yoke and possible damage during transit. Before attempting to dismantle
the optical unit, this plate must be removed by withdrawing screws 12, 13,14
and 15 (LEFT). After slackening screws 6, 7 and 8, the tube mounting and coil
assembly can be removed by turning this assembly clockwise until its movement
is checked by stop 19, after which the assembly can be pulled forward and
Here the tube mounting and coil assembly has been withdrawn from the unit. The clamp 22 holds the neck of the tube, and is secured to the bridge 26 by screws 66 and 67. These screws, and also the screw of clamp 22 should be slackened before withdrawing or inserting the picture tube.
|FRAME NO. 7—TUBE MOUNTING AND COIL
ASSEMBLY WITHDRAWN FROM UNIT.
|FRAME NO. 8—CATHODE RAY
TUBE PARTLY INSERTED.
|FRAME NO. 9—CATHODE RAY
TUBE FULLY INSERTED.
When inserting the cathode ray tube (frame 8) it must be pushed right home so that the earthing tongue 54 makes good contact with the external conductive coating of the tube. In frame 9 the cathode ray tube is in its correct final position, with the E.H.T. terminal at the bottom and the tube clamp tightened sufficiently to grip the tube neck but not too tightly to risk breakage due to expansion of the glass neck.
Before fitting the E.H.T. connector 23, the inside and outside of the glass anode terminal shield should be dressed with Silicone Grease such as Compound DC4, which is readily available to the trade. These preparations are water repellent and have good insulating qualities and are therefore suitable for lubricating the surfaces. The next five pictures show the dismantling of the coil assembly for fitting a new focus coil.
|FRAME NO. 10—THE E.H.T. CONNECTION.|
|FRAME NO. 11—FRONT END
OF COIL ASSEMBLY.
|FRAME NO. 12—PREPARING TO
REMOVE FOCUS COIL.
The first stage (frame 11) is to unsolder the connections on tag plate 68. The tag plate and bridge 26 can then be with- drawn by removing the two nuts and washers 24 and 25. Nuts 27 and 28, sleeve 31, washer 32, spring 33, washer 34, and sleeve 35 (frame 12) are next removed from studs 29 and 30, after which the pot containing the focus coil can be withdrawn.
|FRAME NO. 13—FOCUS
COIL POT REMOVED.
| FRAME NO. 14—REMOVING THE
FOCUS COIL FROM POT.
(Frame 13) The four screws and washers 37, 38 (if fitted) 39 and 40 are next removed. (Frame14) End-plate 43 can now be lifted away from pot 36, and focus coil 44 withdrawn from the pot.
|FRAME NO. 15—FOCUS
|FRAME NO. 16—CONNECTIONS OF
DEFLECTION COIL ASSEMBLY.
A new focus coil can now be inserted, care being taken to thread the connecting tails through the holes 45 and 46 in the end of the pot. The next three frames show the stripping down of the deflection coil assembly for fitting new coils. The first stage is to unsolder the connections to tags 49, 50, 51, 52 and 53.
|FRAME NO. 17—BACK END OF
DEFLECTION COIL ASSEMBLY.
|FRAME NO. 18—DEFLECTOR
COIL REMOVED FROM FLANGE.
Screws 55, 56, 57 and 58 are now withdrawn when deflector coil 47 can be removed from flange 20. When fitting a new deflector coil it is important to.see that its position on flange 20 is the same as that occupied by the old coil. Eight holes are provided on the flange to allow for alternative positions to meet the requirements of different set-makers. The position of the original coil with respect to the mark 'XX TOP' engraved on the flange should therefore be noted, and the four screw-holes used should be marked.
|J.Evans 2003||CLICK HERE TO RETURN
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9th June 2003