Quote:
Originally Posted by Radio Wrangler
With the centremost knob of the time/division stack fully anticlockwise ('main') this is the normal single-timebase setting..... but, if you bring the delayed timebase time/division (outermost ring of that stack) back out of the 'off' position, then the delayed timebase is anabled and will run (if it is triggered) and it will bright up the traces during its run time.
So you can see just when in the waveform you are studying, the fast (delayed) timebase will expand to fill the screen. Move the 10-turn delay pot and the delayed timebase time/div, to get the bright up over the feature you want to look at in detail. Select 'delayed' on the centre knob and this is what you get.
The bright-up mode is great for fiddling with the trigger of the delayed timebase if you need to use it. You get to see what you will get, in the context of the full waveform.
Slow trigger is optimised for trad TV field rates or slower, fast trigger is optimised for trad TV line rates or faster
David
|
I've never used a scope for looking at TV signals, will have to do give it a try as I have various scopes that have TV trigger modes, also should try the 180A too.
All the sweep modes were checked, just didn't post pictures of them as it was quite late at night when I added that quick post, after fixing the trigger problem.
For future reference for anyone else repairing vintage
hp 180 series scopes & others, here are some pictures of the different sweep modes with the 1821A timebase.
Main sweep, red control set to
Main sweep and outer delayed sweep to a faster sweep, than the middle main sweep control, these are all part the triple
Time/CM control. The
CM Delay gives an intensified section on the trace when triggered, which increases the more the ten turn control is increased.
Mixed sweep, red control set to
Mixed sweep and other controls are unchanged, this shows both the normal sweep and the delayed sweep.
Delayed sweep, red control set to
Delayed sweep, other controls unchanged, this only shows the faster delayed sweep portion of the above mixed sweep mode.
Something I noticed when checking all the modes out, is that the light behind the reset switch was never lit, even when set to single sweep. In fact I've only ever seen it lit briefly at power up. The 1821A manual doesn't seem to mention it outside of the single sweep mode.
But comparing the 1821A timebase with the older 1421A timebase, which shares some circuitry in this area, it seems to light when a triggered sweep is running and goes out briefly at the start of the sweep.
David