Agilent E3646A Teardown and Repair

[@risvegliato]

Nice to see diagnosis down to component level rather than just "board-swapping". very refreshing in this day and age. Excellent video.

[@gerrysweeney]

Thanks for the feedback, glad you liked the video. Gerry

[@zx8401ztv]

When you showed your diagram and explained the difference between the two channel monitoring paths, i did think some "common" bias voltage around the opto couplers was ill. Your drawn (no nonsense) style of diagrams are really good, you put me very close to your understanding of the circuit, it made it so dam easy to understand, never put your diagrams down. Using the same resistors for your gain fix was brilliant, they would all respond much the same to heat and if you had used your fluke to match them the result would be just as good as the originals. Very enjoyable, thankyou, no need to reply :D

[@putera131gaming7]

I just found your troubleshooting video. Thank you for sharing. Awang from Malaysia. Electronics lab Technician.

[@saarike]

Excellent repair and interesting fault!

[@gerrysweeney]

Thanks Gary, and thanks for watching

[@gerrysweeney]

You are most welcome, glad you found it interesting. Gerry

[@gerrysweeney]

Good point, I could have and that would have been easier I guess, although it was very easy to stack two in series too. Thanks for the comment. Gerry

[@gerrysweeney]

Thank you for the comments. Gerry

[@tuberlook1]

Just recently found your channel, excellent content, keep up the good work.

[@g1fsh]

That was a great vid very well worked out very methodical and very well explained. Gary

[@gerrysweeney]

Thank you for your feedback

[@ccsignal]

Gerry can you do a video on the calibration

[@hobbeslives]

Just a quick note, the surface mount resistors marked 225 are 2.2M. Nice troubleshooting.

[@gerrysweeney]

hobbes_lives yes you are right, thanks for pointing that out. Wood for trees :) Gerry

[@MAYDAYDEEJAY]

I wish I had full schematics for all my repairs... Gr8 vid indeed ! rgds

[@elboa8]

Good vid. Well paced. Thanks.

[@bobcrooks7178]

exellent Gerry

[@AureliusR]

3K is getting pretty low... it's likely there is something else causing excessive current if that resistor failed open. As you said that is extremely unusual, it would have passed all the factory tests so it has definitely failed in the field. Lowering those values will allow more current - I'd get back in there and put the original values back in. Probably would have replaced the TL074 as a matter of course.

[@AureliusR]

However, excellent video, good troubleshooting man! Must say, with a little more editing work etc. you could have a really good thing going here.

[@gerrysweeney]

Hi, well according to my calculation the current flowing in the 3k+6k=9k resistor is 1.67mA or 0.025 watts assuming the voltage across the resistors is +5 to -10v (15v difference). Thats just 1/5th of the power rating for the resistors and the 5v source and drive capability of the TLO74 is way more capable than that so I am very happy thats a good and reliable fix, no need to change anything. The failure must be physical, a defective resistor from manufacture, it did not fail due to any kind of overload, I am 100% sure of that given the circumstances. Thanks for watching and thanks for the comments. Gerry

[@gerrysweeney]

Good point, although I would have thought they could pick values that would actually work. There would not be much of an infringement if the clone circuit did not work :)

[@snipersquad100]

very interesting, thank you.

[@smunaut]

Nice. But for the resistors you could have just picked any value, put one of them in place of the 20k one then put two in parallel of the same value instead of the 10k. Much easier than the pyramid thing :p

[@CiscoRedstar]

manufacturers do somtimes make deliberate errors on schematics to help trace copywrite infringments.

[@boonedockjourneyman7979]

Do you have an example? There is absolutely no need to introduce errors to ensure enforcement. This whole story is BS.