Video Teardown and Repair of an Agilent 86120B Multi-Wavelength Meter

[Hugoneus]

In this episode Shahriar repairs an Agilent 86120B Multi-Wavelength Meter. The instrument reports “E14 Data Acquisition Problem” which corresponds to a potential internal HeNe reference laser failure. After the instrument disassembly, the old HeNe laser is removed and its optical power is compared to that of a new laser. The measurements confirm that the old laser has significantly deteriorated in output light intensity. The new laser is fitted inside the unit and the error message is eliminated. The free-space optic portion of the instrument is revealed and the principle operation is reviewed. Various components of the Michelson Interferometer is examined.

To test the correct operation of the instrument, a single tone semiconductor laser is applied to the unit and the result is compared to a different wavelength meter. The concept behind the operation of a Fabry-Perot laser is also presented before the signal is applied to the wavelength meter.

You can view the video at: [42 Minutes]
http://thesignalpath.com/blogs/2014/03/31/teardown-repair-and-experiments-of-an-agilent-86120b-multi-wavelength-meter/

Direct YouTube Link:

[echen1024]

Just started watching. Delightful video as always, Shariar! Keep up the good work.

[Vgkid]

Good job with the teardown, and subsequent laser replacement. That machined laser case is beautiul on the inside.

[daqq]

Thanks! It's really great to be able to see what's inside some of the more exotic tech!

[Hugoneus]

It's a shame that the laser has to be replaced when it has just 2dBm difference in output level. Pitty they don't recycle them.

The one thing I do not like about the electronics industry is the enormous amount of waste that goes on (if it fails then just toss it in the bin), the amount is just mind boggling at times.

Yes, I agree. The amount of unnecessary waste is staggering.

[alex.forencich]

It's a shame that the laser has to be replaced when it has just 2dBm difference in output level. Pitty they don't recycle them.

The one thing I do not like about the electronics industry is the enormous amount of waste that goes on (if it fails then just toss it in the bin), the amount is just mind boggling at times.

Yes, I agree. The amount of unnecessary waste is staggering.

That's really one of the unfortunate downsides of the incredibly high level of integration of most products today.  They're very cheap to produce, but impossible to cheaply repair - the 'smallest replaceable unit' has become the entire device, or what might as well be the entire device.  And the really unfortunate part is that this is not limited to consumer electronics.  Many of the modern digital scope designs are based around one single board.  Anything fails on the board, and the swap the entire board.  Such a waste.  And it also means that the resale value of broken modern equipment is practically zero, because it is not feasible to repair it.  My MSO7104A has an issue in one of the converters that prevents the self cal from running (init for talon cal failed on chan1). The fix is a mainboard swap, and they're asking about $6k, which is more than I paid for the unit in the first place.  Go figure. 

[Hugoneus]

... paid for the unit in the first place.  Go figure.

HP/Agilent used to have a component level diagnosis/repair strategy. Now they have a module/board replacement strategy. This shift is the result of what you speak of along with the fact that component level diagnosis is now more expensive than just changing the entire board.

[han]

Great video, i find your video always very educating..
It's a long time since the high frequency oscilloscope video.

it's very amazing that they can precisely measure up to PM resolution.
From your video, the wavelength meter can plot like OSA, and since OSA typicaly using grating and servo controled, Is there any pros and con between each technique?

And why they didn't integrated PMD measurement into the product, since the component required only broadband LED and de/polarizator?

[vaualbus]

Ya since HP become agilent they almost no more release schematics.
(And now that will became Keysight technology who know what will happen!)

An example could be the schematics of the DSA that dave tried to repair. (also because the unit is still in production.)
Probably this strategy of assembly repair is more easy to menage from agilent also because nowdays agilent used a lot of hybrid and asic that are not so interesting on a schematics side.
By they way how much cost the laser source you replace in the instrument?

[Hugoneus]

Ya since HP become agilent they almost no more release schematics.
(And now that will became Keysight technology who know what will happen!)

An example could be the schematics of the DSA that dave tried to repair. (also because the unit is still in production.)
Probably this strategy of assembly repair is more easy to menage from agilent also because nowdays agilent used a lot of hybrid and asic that are not so interesting on a schematics side.
By they way how much cost the laser source you replace in the instrument?

I paid $50 including shipping for the laser replacement from eBay.

[vaualbus]

Thank for the info.

[Hugoneus]

Great video, i find your video always very educating..
It's a long time since the high frequency oscilloscope video.

it's very amazing that they can precisely measure up to PM resolution.
From your video, the wavelength meter can plot like OSA, and since OSA typicaly using grating and servo controled, Is there any pros and con between each technique?

And why they didn't integrated PMD measurement into the product, since the component required only broadband LED and de/polarizator?

Probably because they have other products to cover that. Although, Agilent doesn't make OSA's anymore. It is a shame. They lost that market to the Japanese.