Yes, both those controls work. The real-time mode still looks weird although
now there is only one dot showing during the fall... still should not be any.
It's not weird but perfectly normal. What you see is a Dot response about 75% (upper trace) and slightly less than one (lower trace). Soaome asymmetry in dot response between jumps up and jumps down is also normal and hardly present here. What can be the reason that the real-time mode works fine now when all you dit was 3T77A repair?
I played with it a bit more today. First I I threw together a quick TD pulser
clocked by a 1 MHz crystal oscillator, and calibrated the sweep on the 0.1 us
range using the square wave, then examined the edges after the TD. The
waveform is ugly after the ~1 ns edge, but I know lead length and placement
are at issue).
Yes the cabling is not nice. There will be serious reflections when you use a T-connector as splitter.
Also hooked up my GR 220-920 MHz oscillator to both heads (the S-2 and S-4).
It displays sine waves nicely up to about 500 MHz.
Because of those reflections you must have seen amplitude variations while going though the frequency range of the GR unit.
Photo legend say:
The delay between the two traces is due to the system components, not the cable connecting the tw
(it only accounts for about 4 ns of the visible 10 ns).
The "B Delay" control is hidden behind your cabling...
TD pulser (1 MHz TTL oscillator, trimpot, TD, coupling cap and 47 ohm resistor to a GR cable).
In general coupling caps are not used here and can make things worse.
Why do you think that the falling edge is shown in DSCF0217.JPG?
The level before and after the 1 ns slope look more or less the same to me.
Is it due to a coupling cap with very low capacitance?
Albert
