HP 140A or 140B and plug-ins - diyAudio
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Old 7th April 2010, 01:33 AM   #1
iko is offline iko  Canada
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Default HP 140A or 140B and plug-ins

Hi everyone,
Fond an old HP oscilloscope. It says it's a 140A, and it came along with two plug-ins, the 1411A and the 1424A. BUT it doesn't work. There is no trace when it comes on, except when I press on the trace finder, then it shows. I checked the regulated psu voltages, -12.6V, +100V, and -100V and they're right on.

Anyway, two kind of questions. Does anyone know anything about this unit or the plug-ins. And, would this be worth fixing?

P.S. It turns out that the service manual for the 140B actually matches the psu schematic and the 140A doesn't. Perhaps this is a late 140A or something...
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Old 7th April 2010, 04:59 AM   #2
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This is not a high performance unit but it's built beautifully. I used to have one.

When you press the trace finder button, the trace appears where? That is important; if it's above the middle then the spot is deflected upwards, out of range.

It's worth fixing for the pleasure of it, not for the use of it. Modern gear that outperforms it at a low price and smaller case is readily available.
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Old 7th April 2010, 11:08 AM   #3
iko is offline iko  Canada
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If the plug-in module is not inserted, pressing the trace finder button brings the trace right in the middle; in this case the trace looks like a dot.

When the vertical amp and time base plug-ins are inserted and the trace finder button is depressed the trace for channel A and B show either above the middle horizontal line, or below it, depending on the position of the "up-down" slide button. In this case the trace doesn't look like a dot, more like a short vertical line. It can be moved left or right using the horizontal position control.

It definitely is nicely built. Oh, this particular combination of time base and vertical amp seems to go up to 4GHz, which is better than both my analog and my digital scope. Would be nice to fix it.
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