[Heatercathodeshort]

Part 4. The assembly.

With signs of life in the power, timebase and I.F. chassis it was time to put the whole lot together and see if it worked!

I was lucky enough to have a suitable mask and implosion protection screen. This was slightly different to the original Peto Scott but I felt confident I could make it fit. i sprayed it a satin black as was the original. [As if I would forget]

The original laminated plate was fixed to the cabinet with four diagonal metal straps to the corners. These were secured by small woodscrews to the front of the screen opening.

I have no idea what the original mask looked like or how it was held in place to the tube or gantry. Another mystery is the leather cord similar to the type used to drive Singer treadle sewing machines and springs that appeared to hold the FRONT of the tube in place against the gantry. I will never know.

The replacement laminated glass was one 1/8th of an inch too large width wise and one 1/8th of an inch too short height! It was an easy matter to widen the rebated opening in width and glue a small square of wood at the bottom to take up the slack. Fortunately there was plenty of room to carry out the modification.

The replacement mask was formed to take the implosion screen within the front area. I attempted to fit this in one piece as it was originally intended but this left a gap between the front of the cabinet and the screen. The mask had to be fitted separately.

I placed the mask in the viewing window resting the bottom of it on the timber ledge just below the opening. Next I fitted the CRT centrally into the tight rubber cup making sure no muck had dropped into the space between the glass and the CRT face.

Next the scan coils were correctly positioned over the tube neck and with the inverted gantry complete with it's timber support board I carefully slid this into position over the CRT neck and lined it up with the top cabinet rail securing it with 2BA screws and wing nuts. It is very secure and cannot move when the cabinet is returned to it's upright position.

The power supply was next to be refitted into the base of the cabinet secured with four 1" 2BA screws.

The timebase complete with I.F. was offered up next finally leaving the last item, the control panel until the last.

All the interconnections were made and carefully checked. All that was left was for me to pluck up some courage and plug it in!

Being an AC only chassis, the valve heaters being powered from a mains transformer warmed up very quickly and within moments a distorted but bright raster appeared on the screen I plugged my RF signal into the aerial socket and was rewarded with definite signs of Test Card C.

The oscillator tuning was soon corrected and it didn't take long to reset all the presets to obtain what appeared to be a very nice Test Card. [The TV122 must have been one of the first receivers to display TCC. It was introduced in July 1948. W.W.]The focus is very sharp with the manual control centrally adjusted, quite a rare feat for electromagnetic focus arrangements. The scan coils needed straightening with a twiddle hear and there to get it lined up.

The tube is a straight gun tetrode that is prone to ion burn. There is a circle of discolouration in the center but it is hardly noticeable. I doubt if this receiver was used for more than a couple of hours a day. I have seen well used examples of these Mullard tubes giving excellent pictures with a heavy purple stain at the center. It's just something you have to put up with and is all part of the character with vintage television receivers.

The sound is good and strong with the sound gain control set mid way. The balance between sound and vision was slightly odd but I had checked the I.F. coils during the restoration and found them to be heavily sealed with wax.

Careful examination of the aerial input coil showed the single slug to be at the bottom of the coils screening can. The inner former was completely devoid of any locking wax and then I clicked in. Under certain conditions and especially in fringe areas it would have been necessary to adjust this core to match the customers aerial and co-ax to the input transformer. Peto Scott obviously realized this leaving the core 'unlocked'.

It had probably wound itself down over the years and it was a simple matter to bring the core up midway producing 3mc/s bars on the test card and even more sound!

It was noticed that the line frequency drifted a little over a long period but replacement of the EF42 line oscillator completely cleared this up and other than a slight readjustment of the customer focus pot, remained incredibly stable. As the temperature of the winding increases, so does the resistance of the coil. This results in a voltage loss needing a correction with the focus pot.

The interlace is excellent maintained throughout the entire range of the frame hold control.

The pictures show the general reproduction of the Peto Scott TV122. The pictures are very bright considering the low 5.5KV EHT.

The final part will include a few details of the minor clean up etc and the final evaluation of this rather grand television Receiver. John.