On further examination, I think I found the reason.
The negative pulse edge of the high amplitude output develops
considerable bowing above about 65 volts. When it is trimmed for a
maximum output of 5.2 volts into 50 ohms, the maximum output is 64
volts into a high impedance load. The specifications require an
output of 60 volts or greater unterminated and 5 volts or greater into
50 ohms.
On Tue, 17 Jul 2012 03:43:22 -0000, "Patrick Wong" <patwong3@...>
wrote:
Hi David,
Congratulations on restoring proper operation to your unit.
Since a spec is the high amplitude output is adjustable up to > 5V into 50 ohms, I suppose that is the reason that the adjustment procedure has you setting the max output at 5.2V, giving you 4% over-range.
If you are asking what is the utility of the high amplitude output, there are at least a couple of uses in the analog 24xx scope calibration procedure:
1. CAL 06 - Vertical Transient Response, where the high amplitude output powers a tunnel diode pulser. A maximum voltage setting is required from the high amplitude output here.
2. Adjustment of CH1 and CH2 input capacitance, although in this case it looks like only 300 - 600 mV signal is required.
Patrick Wong AK6C
--- In TekScopes@..., David <davidwhess@...> wrote:
...My question concerns the high amplitude output calibration. Why is it
even adjustable via R790? The output level has no important
application that I can see so why bother adjusting it to 5.2 volts
into a 50 ohm load?
David Hess