jts1957
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Aug 28, 2009, 5:18 PM
Post #86 of 141
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Re: [bogart219] Toshiba hypermodule
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Remember: when looking at the waveforms pictured in the service literature, bear in mind that those "Waveforms are taken receiving color bar signal with enough sensitivity."
A lot of the following is probably more than you need to know, and I'm trying to "keep it simple." We'll use CH1.
On that scope make sure all "Cal" are kept fully CW (Volt/Div & Sec/Div inner knobs). Not sure if that one works exactly same as mine, but on mine, the digital (numeric) reading is NOT affected, but the ability to double-check the reading by counting the number of squares and multiplying by volts/div (and multipling by 10 if using a x10 probe) etc., IS definately affected.
The CRT screen has a grid of squares over its face. The "/DIV" stands for per "Major" division.
VOLTS/DIV: is for setting the number of volts represented per division. You'll want to adjust this to obtain display waveform approximately 1/3 to 1/2 of scope's screen tall (you can use POSITION up/down to center it). Under Volts/Div control is a slide switch which we'll need set to "AC." The rest of the push/slide switches (except in "trigger" area) are fine as pictured/setting shouldn't matter. (That's probably gonna come back to haunt me.  ).
SEC/DIV: Note the "ms" and "us" and its dividing line between ".1" and "50." Is speed of beam= slower CCW from that point/faster CW from that point. "ms" is milliseconds and is more to the "vertical" rates (vertical output circuit & frames of video, for example). "us" is microseconds and is more to the "horizontal" rates (horizontal output circuit & horiz. lines of video, for example). Suffice it to say, most of what we'll be looking at will be in the "us" range. Set on "5us" for now.
Which brings us to TRIGGER. I have never "trusted" many of the "auto" features on my scope, with the exception of this one.
I am not positive your scope works this way, but the following is my best educated guess: Everything below "HOLDOFF" pertains to the "EXT INPUT" jack. SLOPE is whether is triggered by positive or negative polarity of signal (usually set to match the video's sync pulses). Trigger MODE should be fine where it is pictured (for now). LEVEL & "TRIG'D" Light - in moment.
So procedure is as follows: connect scope to the point of interest. Adjust VOLTS/DIV to obtain a half-height display, centering it vertically on scope screen. Turn SEC/DIV to where waveform is closest to becoming stable and/or you have 1-2 "cycles" of the waveform displayed. Then go to "Trigger LEVEL" and turn from one end to the other - Waveform will "lock" and "TRIG'D" light will light simultaneously when you hit the correct point. (This last step "may" all happen automatically).
I've got to go do something, I'm gonna let this sink in for awhile. Will post further later tonight.
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Location: Far, Far Away
(This post was edited by jts1957 on Aug 28, 2009, 5:22 PM)
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