Re: How to Test an NE75 Neon Lamp
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After reassembling the [now clean] time-base, DS101 is still not illuminated.? I've checked the +100V rail and that checks at 99.x volts (don't remember the exact fractional part).
I had not previously removed the top cover to observe the time-base.? With the cover removed, pressing the RESET switch causes a neon lamp (V105?) towards the back, right side of the main circuit board to illuminate so at least part of that circuitry is working.
I'm guessing the problem has something to do with Q109.? The -100V rail appears to be a crucial part of that circuit too.? I didn't check that rail but intend to do so tomorrow.
Thanks, Barry - N4BUQ
From: "Barry" <n4buq@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Tuesday, March 26, 2024 11:48:38 PM
Subject: Re: How to Test an NE75 Neon Lamp
I got around to testing that lamp.? With R135 and R136 still in place, I connected to the end marked +100V and the other side of the lamp to ground.? The lamp fires very close to 90V so it's still good.? Looks like I get to start troubleshooting why it doesn't work (presuming it still doesn't) when I get the plugin reassembled. Thanks, Barry - N4BUQ
From: "Barry" <n4buq@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Tuesday, March 26, 2024 8:15:24 AM
Subject: Re: How to Test an NE75 Neon Lamp
Ozan, David, Thanks so much for the replies.? The two resistors (R135 and R136) are both mounted with the lamp so I can power it with R135 in series.? Since that lamp should be lit in both NORMAL and SINGLE and both modes appeared to be working, then I'm even more suspect of the lamp.? Testing it out of the circuit will confirm that one way or the other. Thanks guys, Barry - N4BUQ
From: "Barry" <n4buq@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Monday, March 25, 2024 11:33:32 PM
Subject: How to Test an NE75 Neon Lamp
The ready lamp for SINGLE triggering mode in my HP 1421A isn't/wasn't working. ?I'm not sure what the problem is but I have removed the front panel to clean it and before I reinstall it, I'd like to determine whether the lamp is good as it's fairly messy to remove the front panel to get to it.
From what I can tell, there's about 50V across that but not sure if that's when the lamp is supposed to be on or off so I'm not sure if that's enough to turn the lamp on.? I'm not finding much in the way of specs for an NE75 either.
Anyone know how I can test it? Thanks,
Barry - N4BUQ
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