TV Ambassador TV2

[Geordie McBoyne]

The circuit diagram of the Baird T5 frame timebase. Compared with the Ambassador TV2 only a modest amount of power is required to deflect the electron beam in the 40 degree CRT operating on 5KV.

Geordie McBoyne.

[LENINGRAD T2]

Tests carried out:
- the wiring diagram of the receiver differs slightly from reality
- separator circuit - correct
- vertical deflection - correct
- horizontal deflection - reduced oscillator frequency, outside the adjustment range - change in the value of the resistor R66 - correct result, but without affecting the image
- video sections - generally without significant irregularities, but I found an additional resistor with a capacitor soldered non-factory within the CRT socket, parallel to R28. After removing these two elements, the correct image appeared on the screen without horizontal stripes
- no sound - replacement of a new 6P25 with another new one solved the problem - poor emission. Fortunately, I originally bought two
- suddenly the image disappeared - subsequent tests showed a problem with the R27 at the V6 final vision amplifier. He looked good overall. When touched with a screwdriver, it broke in half and then turned to dust. After replacing the image came back
- tuning all sections of the TV according to the instructions - improving the picture and sound
- the picture deteriorated, slight tremors - the reason was the V9 in the audio system - 6LD20. After replacement, the image is stable. H-K short circuit
- From the very beginning I was intrigued by the vertical deflection transformer with vertical arms near the neck of the CRT. Their distance from the neck is quite large, about 25 mm. The transformer arms have a large adjustment range, at least a few centimeters horizontally. Changing their position by 2-3 cm does not affect the image at all. This system therefore has high energy and at the same time inertia/tolerance. I don't know what the blades on both ends of the transformer's arms mean - see photo
In the end, there was still the problem of collapsing the image on the left.

Baird T5 stimulates circulation. It is a pity that the owner of the TV Ambassador did not have two of these in the package.

                           

[Murphyv310]

Well done Adam.
I like your methodical approach and how it is the best way to learn.
It's a good picture indeed bar the line on the left, a little bit of velocity change, there could be an adjustment for this, which should be seen in the circuit diagram or a resistor/capacitor network around the line transformer.

[LENINGRAD T2]

Thank you all for your help. There is little left to do.

[LENINGRAD T2]

Re-checking the separator and line time base elements did not bring anything exciting. I checked the vision circuit again. Adjusting L13 gave a big improvement in the image.
   

[Murphyv310]

That's a big improvement, not far away from being a perfect picture.
Would like to see the video waveform after the detector.

[LENINGRAD T2]

The last adjustment improved the image curl on the left side, but unfortunately also made it very unstable. In addition, there is still a vertical glitch on the left side.
   
I went back to the original adjustment, which stabilized and sharpened the image, but again showed its curl on the left side. The nature of the disruption is well illustrated in the photo below.
   
This problem is not dependent on the video signal, it is very regular and closely related to the horizontal deflection system. Occurs on a raster. I checked the capacitors in the line time base, replaced them just in case with new ones and nothing. The output transformer also seems fine. I think the oscilloscope found the fault. In the picture below you can see two waveforms from the horizontal deflection coil circuit. The first when the coils are connected and the second without them. The oscillogram shows a disturbance at the beginning of the cycle, probably caused by a permanent short circuit in the coils. The resistance of the coils slightly deviates from the nominal values.
   
   

[Murphyv310]

Hi.
A bit of ringing on both waveforms. Left hand foldover can sometimes be a hard one to crack. Check C45 and R65 in the first instance. Also try running the set for an hour or so and see if the issue gets worse or the width of the picture reduces.
C47 is also a small possiblity but worth checking or replacing if you haven't already.

[Murphyv310]

Shorted turns would usually kill the line stage in a design like this with a self oscillating line output. I personally think it's dampness in the LOPT you'll notice a drop in width after a long run if so.
Passing perhaps 20ma through the overwind for a few days to get it warm, usually will effect a cure.

[LENINGRAD T2]

Thank you Trevor for your valuable comments. For clarity, I present a real fragment of the scheme from my TV. I checked all elements in the horizontal deflection system. I also did a lot of tests with inserting subassemblies with slightly different values. The vertical glitch on the left side was not affected. Only increasing the capacitance of C2 resulted in an extension of the disturbance.
What I also considered was:
heavy damping symptom - this may be the cause of the changes on the oscillogram that I showed earlier. However, the image then tapers to the left but does not wrap
rings - there may be white stripes on the left, but probably without wrapping the image
slow flyback - may cause the image to wrap !. I don't know how to test it yet.