Indeed, colour TV installation back in the day was not just a case of taking it out of the box and plugging it in. A straightforward installation would take about an hour if everything went well, much longer if it didn't. Main procedures were degaussing the environment, then static and dynamic convergence adjustments.
Lets not forget what we are trying to achieve. As near to perfect alignment of three streams of electrons that are being aimed and fired at 150,000 or so minute tapered holes to strike 400,00 phosphor dots. The beams are swept from top to bottom and side to side across the screen and all must got through the right holes at the right time and hit the right dot. Its all done with extremely high voltage under electromagnetic control. You could learn the mechanics and procedure of colour TV alignment but the true skill was more of an art form.
The receiver was installed in the desired location and then switched on and allowed to warm up for a few minutes. You then had a good look at the picture looking for obvious alignment problems, sizing up the job so to say. You would make a mental note if there were any major problems that you must correct first. Assuming there was nothing major but armed with your initial observations you could then proceed with the installation.
First job was to degauss the screen and the environment if required. The shadowmask within the CRT was only microns thick and could easily be affected by local residual magnetic fields if present. This could be from radiators often installed under the window and fairly close to the TV receiver. Electric storage radiators could be a menace as they had heating coils within unlike a water filled central heating radiator which is just a big chunk of metal. You could get problems when large storage radiators fired up. To mitigate magnetic build up in the shadowmask, the CRT's had degaussing coils fitted around the back of the glass envelope. These coils were energised each time the receiver was powered on from cold and served to rid the shadowmask of residual magnetic fields. They could not cater for external objects that may well be holding a magnetic field. A small hand held degaussing coil was used to rid any local metal objects of residual fields. It was mains operated with a long lead and was about 9" in diameter with a push button switch in the centre to energise the coil. You started the coil with circular motion close to the target object then backed away to the other side of the room. I always did a few passes to ensure that the room was free from residual fields that could affect the next stages of the alignment. Waving an energised coil around near to the TV degaussing other objects could have a detrimental effect on the CRT itself as its internal degaussing cycle had already finished so it was usual to make your last pass on the screen itself.
Next stage was static an dynamic convergence and required the use of a pattern generator. This replaced the broadcast signal and provided various test displays for alignment of the CRT and associated circuitry. You could switch in a pattern of dots, vertical and horizontal lines, cross hatch and chequerboard displays and white screen.
First job was to get the static convergence as near as you could. Static convergence was controlled by circular flat magnetic rings installed at the rear of the deflection coil assembly. The rings were in line with where the electron streams emerged from the guns in the CRT neck and controlled the direction of the streams towards the shadowmask. There was an inherent problem with 90 and 120 degree CR tubes in general in that the front of the screen was curved, not much but it did have a knock on effect on convergence, because of this, any adjustment were best case or as good as you could get it, it was impossible due to the overall design and manufacturing tolerances to achieve perfection. You aimed to get the best alignment covering the largest area outward from the centre of the screen. The magnetic rings were arranged with offset fields so each affected it neighbour, you could adjust for each colour in turn by just driving a single gun using the dot pattern to ensure each was going to the correct location then switch all three on and use the white screen for final adjustment.
All of these adjustments were done from the back of the set so we carried a framed mirror that we could set up in front of the receiver to aid in the adjustments. Hard work reaching round the back and trying to look at the screen on a 26" console job!
Next job was dynamic convergence. This was to cater for the discrepancies at the edges so to say and was controlled electronically with various adjustments available usually on a bespoke panel. Most manufacturers had a printed pictorial overlay that sat above the adjustment potentiometers that indicated which aspect of the convergence it controlled and in which area of the screen. The adjustments were actually controlling additional coils which were integrated into the assembly around the CRT neck. They were also interactive to some degree so it was generally a case of revisiting each in turn to strike a happy medium. This is where the artistic bit comes in. You used the vertical and horizontal line patterns from the generator first then finished with the cross hatch paying particular attention to get the best convergence you could around the edges. The coils acted on the electron streams from the guns further down the CRT around the position where they emerge from the neck into the main envelope of the CRT and could have an interactive effect on the original static convergence so it was a dual process operation to keep checking back to ensure you were not robbing Peter to pay Paul.
Last job was to adjust the white balance and this was best done with the customer in attendance. If you did this unattended you often had to go back. White balance or hue is in the eye of the beholder. Equal drive of red, green and blue will produce white, or thereabouts. Balance should be adjusted to the satisfaction of the customer, they have to sit and watch it and nothing irritates more if they think it is wrong. My mate Colin always used to err on the blue side when he installed, I used to lean slightly towards the red spectrum. If the customer was present you also got the opportunity to show them how to adjust for correct saturation with the user controls. Without this basic info the first job when visiting many sets was to turn the saturation down, colour does not mean full on number 11! They were always surprised to learn that you start with the colour turned off and the set in B&W, adjust the contrast and brightness first for a full range of grey tones then adjust the colour (saturation) control for best skin tone.
If all went to plan the customer ended up with a display that was the best it could be and they knew how to adjust the user controls correctly. As installation engineer you were usually better of by at least one brew and a few biscuits or the odd home made bun.
Excluding electronic failure you may have to return at some time in the future to repeat degaussing when the internal defence circuitry of the CRT was overwhelmed by vacuuming operations and other electronic interference in the room! Oh and incontinent cats and flying rabbits, but that's another story..... could write book, exploits of TV engineer..
PY500 and PL509, swapped a few of those in my time China.
We had to degauss that monitor too!
