🔴 HP 1740A Oscilloscope Repair - Part 1 - No.1313

[@poormanselectronicsbench2021]

@ 15:00 you are most likely set to "B" trigger, so, when you switch to the A input, its not seeing anything to trigger and won't sweep. I've owned one of these since the mid 90's, its been serviceable, but is dated of course. Still nice to see the inside and serviceability of it. If you wanted to see both channels sweep, set your display to "alternate" or "chop" , trigger button to either A or B, or both down for "comp", upper right sweep buttons to "auto" , or "normal", and make sure the MAIN button is depressed / in

[@Ozymandiuus]

Watch out for physically leaky smaller electrolytic caps. On mine, there was one that physically leaked its electrolyte goo and corroded a number of traces on one of the boards. I can only imagine that it was also electrically leaky as well, but once they start spitting up their lunch, there's little point in testing any further. Definitely one of the finest scopes of its day. Great to see this one getting a new lease on life. P.S. I also suspect you have AC noise on one of your DC rails, based on that noise when you pressed the beam finder. I'd check for excessive ripple on your DC supplies. Might have a an open filter cap in the power supply.

[@allthegearnoidea6752]

I have one of these I think these are one of the best analog scopes and very reliable. They have a really fine line for the display

[@randylemn]

Those dark resistors change values until they open. Back when I worked on those resistors would change values and cause the circuits to be non linear. There was also one on the sweep board that would cause the sweep to be nonlinear across the screen. Back when I worked on these there were some service notes HP distributed that covered some of these problems. When you get it running and it will not make rise time/ Bandwidth my favorite note was to massage the delay line (Black roll of coax in the middle of the unit) and it would make bandwidth again. Good luck

[@davidv1289]

Nice scope! Part of time you were trying to get it to trigger you were adjusting the delayed sweep trigger knob (in the grey area of the front panel) Regards, David

[@GeorgeWMays]

Love it.... Keep going. Thanks for a cool video. Much appreciated.

[@analog_guy]

I have one of these that still works just fine, except: The plastic feet on the back have embrittled with age and have broken off. The scale illumination does not work. (Probably an easy fix - I haven't bothered with this.) On occasion, the trace shows some noise in the vertical direction. When this happens, I whack the scope on the left side and this clears the problem, at least for a while!

[@canadavey]

Where did you get those probes for your Atlas ESR70?

[@TheDefpom]

@@canadavey they are just some 2mm adapters, they are used on normal multimeter probes to convert them to fine points, I probably got them on AliExpress, might be called a needle probe or something like that.

[@bblod4896]

The switches and buttons on darker gray right side are for the delay only.

[@hjvanderlinden]

I don't have time to watch the video. I had a couple of these and they are awesome (really good phosphor). What happens with these is that the connector at the end of the CRT becomes problematic. Giving the connector a nudge often helps to get a trace back if there is none. Another defect source is the vertical amplifiers. IIRC these are custom parts and cannot be replaced.

[@kiore22]

Having a little giggle to myself around the 3 min mark when metal shield around the High Voltage area jams up against the hopefully discharged pcb

[@andersvandegevel8355]

If whatever is in there isn't dead, ask Rob for a loan of one of his rifles! xD

[@bblod4896]

You're going to have nightmares of spiders crawling on you when you sleep 😂

[@ricksampson6780]

They don't make'em like that anymore!

[@sebastian_harnisch]

Fortunately. But I know what you mean :D

[@bblod4896]

This video looks familiar 🤔

[@TheDefpom]

@@bblod4896 only some of it, it started off as part of a live stream.

[@bblod4896]

@@TheDefpom Yep, I thought my brain was fading faster 🤯

[@TheEmbeddedHobbyist]

look's like the 121K in parallel with the 197k simples peeps 🙂

[@andymouse]

I should watch all the vid ! I see what you mean now the 740 R is the 121K in parallel with the 197 K....show your working out !!............. Squeak !!!

[@TheEmbeddedHobbyist]

@@andymouse i thought that he said it was 74K maybe i need to remove the cheese stuck in my ears.

[@andymouse]

@@TheEmbeddedHobbyist He did I wrote the comment without knowing the whole story ! my bad and stop putting it in your ears for goodness sake ! :)

[@andymouse]

:)