OK it seems that Sam is happy for now so here is my problem.
Symptoms and my observations on my problem on a Topward 7021 oscilloscope recently purchased. All these comments relate to components on the first diagram.
1) No trace at all, not even a flash on the crt during startup
2) The neons DS01 and DS02 (centre of diagram 1) were flashing and crackling every 30 secs or so which I took to mean they were going overvoltage. That has stopped now but they still flash gently on shutdown.
3) The mains transformer voltages are all good and the horizontal and vertical amps are generating good voltages that swing nicely when the pots are turned on the front panel. All good there so I started on the HT circuit.
3) I disconnected the socket from the back of the crt and inserted a 100M Ohm resistor into the cathode socket but read zero voltage to ground (or from the grid) so I started looking at the 2000v supply
4) The HT transformer T001 is running cool and with no signs of burning. I have injected a small sine wave signal into the primary and I get 20 x the voltage on the secondary at 20kHz. I don't know what frequency the input is supposed to run at so I am guessing here but I believe this means that the transformer is ok.
5) The transistor Q003 (an oscillator I think) runs hot but tests fine but I replaced it anyway with no change. The signal at the base of this transistor (measured with my other Hitachi oscilloscope) makes no sense to me as I would expect to see a nice sine wave but I get a muddled trace apparently with some high frequency content that my scope can't display. I will try and take a photo to post here. I tested the components around the transistor (in circuit) while the transistor was out and all looked fine.
6) The 16v supply into inductor L001 near the transformer is running at around 18v and has 2v peak to peak ripple but I assume this may be acceptable. I would expect worse if the smoothing capacitors had gone.
7) The 12v supply into op amp U002 are fine until you get near pins 2 and 3 where the dc voltage picks up a lot of noise, making the trace blurry. But, if I hold the scope probe in the air anywhere near the transformer there is a lot of interference so this may be expected. Any opinions?
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/cool.gif)
My attention is now on the blanking circuit to see if that is stopping the HT. I get a small dc voltage just before Q16 where unblank signal A comes in (far right of the diagram) but I don't know what to expect there. The diagram shows another unblank signal B but those components are not present on my board. The unblank signal on my Hitachi is an alternating square wave signal but i don't know if this should be similar. Any ideas on whether failure to generate an unblanking signal would stop the circuit generating HT? I don't understand what the circuitry is doing after the unblank signal comes in and it looks like high voltages so I am not probing around in there.
Any ideas on what to do next would be very much appreciated.