SOLD (US): Tektronix 7403N Oscilloscope Mainframe; 35 USD - Page 1
Forum section: electronics / general

author: ramenbytes
author_rank: Contributor
timestamp: October 12, 2022, 07:12:51 pm
content: In good condition to my knowledge, but in need of maintenance and minor repairs. No modules included. I've tested just about everything except the graticule electrical contacts for scope cameras, and everything appears mostly functional except for the button lighting, which doesn't work from what I can tell.Issues I'm aware of:Intensity knob only has an effect between about 12 o'clock and 2 o'clock. Below ~12 o'clock the beam disappears, above ~2 o'clock the beam doesn't get any brighter, just changes thickness/focus, and eventually dims a little.Graticule Illumination doesn't kick in until around 9 o'clock, and past that isn't entirely linear so at some points turning it up might result in a small decrease or nothing at all until turned up further. On average it increases though.Aesthetically, one of the plastic caps at the end of the handle is a little cracked, and there is some paint missing off the top from a piece of painters tape that was there. Aside from that some minor marking here and there. Bit of dust/dirt/grime here and there. On the back by the cordwrap feet someone scratched/engraved something that looks like a serial or stock number. At least some screws have marks on the heads, but I haven't noticed any obviously stripped screws, though I haven't looked everywhere either.Calibration or conformance to specifications is not known. The plug-ins I got it with (not included) all have stickers claiming they were calibrated in '85, so I'm guessing that was the last time the mainframe was calibrated too.Notes:I don't know the history of this scope, and it's possible someone tried working on it before it came into my possession. I got it from a guy at a ham swap meet, and he was getting rid of it to make space for new acquisitions. I'm getting rid of it now since I need to sell some stuff, and I can live without this particular scope.Z-Axis test consisted of feeding a sinusoid into the external z-axis input while feeding another signal into a vertical plug-in with appropriate timebase and visually checking that the signal got blanked or brighter sinusoidally. Didn't verify input voltage range or anything like that, might be smaller than spec'd range from what I recall.There may be other issues I have not found or noticed.Pictures below, and in the reply to this post.Asking 35 USD; demo and pickup in Los Angeles County or Long Beach, California, USA.(EDIT 17/Oct/2022 11:16 GMT-7: reduced asking price from 75 USD to 50 USD)(EDIT 28/Feb/2023 13:31 GMT-7: reduced asking price from 50 USD to 35 USD)

author: ramenbytes
author_rank: Contributor
timestamp: October 12, 2022, 07:22:21 pm
content: More pictures attached, to show markings and things like knob positions on maximum intensity. The triangle wave picture shows external z-axis modulation of an FM triangle wave being sent into the front. The modules in the pictures are no included, and are just there because I was testing.

author: ramenbytes
author_rank: Contributor
timestamp: October 12, 2022, 07:24:38 pm
content: Last few pictures. Not sure why some of the pictures are being rotated.

author: ramenbytes
author_rank: Contributor
timestamp: October 17, 2022, 06:18:44 pm
content: Reducing the asking price to 50 USD to try and sell faster.

author: ramenbytes
author_rank: Contributor
timestamp: February 28, 2023, 09:33:21 pm
content: Further reduced asking price to 35 USD

author: ramenbytes
author_rank: Contributor
timestamp: May 20, 2023, 10:24:41 pm
content: This item has been spoken for.