[Electronic M]

I'm not going to use tube numbers, but lets assume you have a B&K 1076/1077 analyst like I do (or a ballsy test pattern generator, and a way to modulate it to IF and RF).

You DO NOT need to disconnect anything...But if you are working on a hot chassis set powering that set through an isolation transformer is recommended.

Lets start out with a video chain (in a monochrome TV) and assume it has (and starts at) a SS diode video detector diode, a 1st video amp tube and a second/output video tube. You would start by injecting at the detector diode or grid of the first video amp tube (in the common case that the diode is hidden in a can). If you can see video on the screen assume everything between that point and the CRT is working correctly...If you don't get video move down stream and inject at the plate of the first video tube, then the grid of the second video tube, then the plate of the second tube then the video modulated element of the CRT until you have signal on the screen... You will need to start with a low video level from the generator and crank it up as you head down stream to the CRT. Feel free to test points in the signal flow between the plates and grids...You can sometimes isolate the individual component at fault that way.

Now lets assume a set with a standard 2 tube tuner and 3 stage IF. A B&K analyst's IF generator should have the stones when injected at the antenna terminals to pass through the tuner all the way through the IF and onto the screen in a working receiver (assume tuner or AGC issue if it does this on a bad set). Assuming that does not work inject into the IF end of the tuner to IF coax cable and then the grid of the first IF. If you get signal there assume IF cable and or tuner are bad. If no signal there inject at the 1st IF plate, then 2nd IF grid, then 2nd IF plate, etc till you hit the detector. The parts just before the first injection point that gets you first get signal on screen are suspect. On dead IF/tuner work I set the RF/IF output of my B&K on max so something will get through if it can. On some sets there is not enough IF gain between the plate of the second IF and detector to get any signal to the outputs....This is where using a scope in conjunction with the generator can be important. When looking for intermediate points of injection I use the schematic to get a feel for signal flow and select points of interest.

Using your gear on a working set (especially if it is the same chassis as the bad set) is a great way to get the hang of the process and a feel for what to expect from which points.

I don't get much bad tuner problems so I'll let those that know how to fix a tuner chime in on that.

On tuner and IF issues always remember that the AGC sets the gain somewhere between max achievable and zero gain/attenuation so a good IF can act like a bad one if the AGC system is screwed up.

Hope this helps.

EDIT: since conversation occurred while writing the above I will address that. You can NOT trouble shoot a dead tuner/IF with ONLY a video generator. You need a source of modulated RF/IF signals (such as a B&K 107x series) to do that.