PRT-3 CRT Tester

[ostlar]

So I got my hands on a PRT-3 CRT tester from PR-Teknik Radio AB, supposedly an old company in Sweden that specialized on radios.
I cannot find any information about either the company nor the tester, and the previous owner did not know much about it.
I have found that the B&K 465 is pretty similar in both functions and schematic, but this is a pretty basic tester, so not a surprise.

This is a thread where I will try to get it working, and might ask for some help from more experienced people, you guys know a lot that I don't.



It came with an 8 pin Loctal socket and no adapters, but my idea was to make an universal connector with eight clip hook ends.
However, with no schematics or documentation, I have some issues finding out which is which.
Some of the wires are obvious, like red, green and blue cathode connections, as they come directly from the RGB swich.


High resolution version here


This is what I have found so far:

• Brown - Red cathode
• Yellow - Green cathode
• Purple - Blue cathode
• Orange - Heater, variable voltage from the switch
• Green - unknown, goes to the top section of the function switch at 7 o'clock as the common for the selector, noted that it was melted in the 8 pin Loctal connector
• Red - unknown, goes to the mid section of the function switch at 9 o'clock
• Blue - unknown, goes to the common on the RGB switch, which also goes to the top section of the function switch at 9 o'clock. So this wire will have the same potential as the cathode being tested. Isn't that logically G1?
• Black - Heater ground, goes through the life test switch which is normally closed

One of these has to be G1 and G2. I wonder what the last one could be, as most of the tubes I've had experience with only has 7 pins in use.
Does anyone have any insights in this?

I am in the process of drawing a schematic of the whole thing, but kind of hit a wall when I noticed the large capacitor was missing its + lead, and there are no loose wires.
The function switches are confusing me a bit too, as it is divided into three sections, and each section has a top and bottom copper "cam" that are different.
So each section has two switching lanes. I've started drawing it on paper, but quickly realized that I'm struggling with placement of components and wires, and it becomes a mess, so I am considering going digital on this one.

My goal is to get this working, and be able to check the emission on some of the old TVs I gather in my collection.
I have an old Philips TV 1201 that is almost completely missing its red, and I am suspecting a tired red gun as the red circuit seem to be okay.
It's destined to be trash, so a rejuvination test on it is a risk that I am willing to take.

I have ordered new electrolytic capacitors for it, so I'm hoping to be able to retrace what is G1 and G2 until they arrive.