Using "Z" Mod on a scope.

[Murphyv310]

       
Hi.
I'm sure not many of us has ever used the Z mod feature on our scopes.
I have a spare Hitachi V212 and have been using Franks Test card generator to play around with it.
As Franks generator has separate line and frame sync outputs the frame pulse can be fed to the X or channel 1, line to external sync and the video to the Z mod via a suitable phase inversion stage, one NPN transistor will do fine.
The V212 though has what is called a blanking input and all you need to do is to bypass R901 with a 22uf 25v cap.
I intend building a field oscillator and sync separator for composite video inputs.
My CRT is a bit low but I've another so it will be changed soon.
There is no reason why this wont work on all electronic standards and some of the mechanical TV line standards.

[ppppenguin]

Yes, I have used the Z input very occasionally. Ideal for displaying oddball TV standards for which you don't have a monitor.

[Mike Watterson]

I found I could add X out and Z in on the blank panel on my Hameg. The schematic had the locations marked. I didn't figure Y out yet. I first amused myself doing this in the BBC CTA in 1970s.

Handy for not just TV, but you can feed Z with the Pen Up/Down signal on some random piece of gear. Or have a "marker" function, (calibrated tuned filter with detector, such as "Dip Meter" on the output of a sweep gen driven by X (to brighten or dim the trace). A detector on the equipment under test (RF or IF etc of TV or Radio) feeds the Y in.

[Kalee20]

Yes I've done that! Got the photo somewhere, taken with a proper scope camera.

I used the scope's internal time base for line scan, and a second scope (Tek 545B, which helpfully has a time base sawtooth OUTPUT connector) as frame sync. Then video went to z-input.

[`FRANK.C]

Great thinking Trevor.
I never thought to try that. How did you do the saw tooth for the frame.

Frank

[Gingpeakin]

Shortly after I started work they had a complete replacement of all the scopes in the maintenance department. There were loads of 465s and a couple of 7603s, a 7704A and a 7623A with as many plug-ins as a young bloke could wish for. These exotic 7000s were kept locked away from the clumsy oiks like me but I was bored one quiet weekend (they usually were then) so I hooked up the off-air feed and used one to invert the video, another for one timebase and and a third to do the other and display the picture. I left them out Sunday night knowing that I wouldn't be back until the following Tuesday. There was such a fuss. Many years later they found their way to me via the skip where I still have them (with most of the plug-ins) along with the oldest of the scopes they replaced - a 535 from 1954.

Ging

[Murphyv310]

Great thinking Trevor.
I never thought to try that. How did you do the saw tooth for the frame.

Frank

Hi Frank.
The frame sync pulse from the generator works fine to give me scan, it's a bit hit and miss due to all the dc component tbough, linearity is bang on though. I'll fit the new CRT tomorrow and will make a proper field generator for different field rates.

[Mike Watterson]

555 timer?
Neon, capacitor and resistor?

[Murphyv310]

555 Sounds good Michael.

[`FRANK.C]

The results are very good from just the pulse.
This is my shameful effort from a while back, it's just the video with a lot of mains hum on it .

Frank