Author Topic: 16GHz Tek DSA71604C. What were they thinking?  (Read 2613 times)

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Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #25 on: October 02, 2019, 09:22:18 am »
After running SPC, the excess noise seems to have disappeared! Interesting, given that it was last run in May and passing, so it should have been pretty close.

I'm running it on an external monitor as the backlight is not working for some reason. It's getting +12VDC, so I'll have to find a datasheet for it to see if the enable signal is asserted.
Jay

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Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #26 on: October 02, 2019, 09:25:20 am »
I'm leaning toward this one.
https://www.digikey.com/product-detail/en/kemet/C1210C107M8PACTU/399-11631-1-ND/4918887
10V X5R which is twice the rail voltage.

I'm sure that would be fine.
Although its 66% down at 5V, so for future reference, this one for example would be equivalent (~33uF): https://www.digikey.com/product-detail/en/taiyo-yuden/EMK325BJ476MM-P/587-5436-1-ND/7067112

Thanks.
A 16V part can be found in a 1210 package. Perhaps that would be a better part?
Jay

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Offline RoGeorge

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #27 on: October 02, 2019, 09:35:08 am »
I guess that's an RF absorbent foam (antireflective material) in the OP pics.

Without the dampening RF materials, reflections from the enclosure will create unwanted/uncontrolled resonances, thus ruining the linearity of the circuit/instrument, which translates in a distorted waveform on screen or fake spectral indications.
 
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Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #28 on: October 02, 2019, 10:19:30 am »
So the fuse is blown on the inverter. Probably a pre-existing condition that the customer did not disclose.
NEC 121PW181
https://www.newark.com/nec/121pw181/inverter-5ma-lcd-module/dp/01P4251?CMP=AFC-SF-OEM

No real stock from reputable vendors.
I'll order a fuse and see if it opens up again. It's 3.5mm in size. Datasheet says: rating 1A, fusing current 2A.
Part # CCP2E20HTTE. Annoying datasheet does not allow copy-and-paste.

There's some inverters available on Ebay. The customer is in a rush (I think they are military) so I've been buying parts with over-night shipping.
Might just buy an inverter as well, JIC.
Jay

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Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #29 on: October 04, 2019, 11:41:15 am »
Using a plastic bag for a template, a sharpie, and an X-acto blade I made the new foam inserts.
Not perfect, but it should do the trick.
Jay

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Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #30 on: October 04, 2019, 01:02:50 pm »
Lastly,

Replaced the fuse on the inverter and it did not blow again.

1. Shown is a 6GHz 300mV sine wave from my SMT06.
2. The obligatory rise-time of 55.38pS on Leo Bodnars excellent BNC pulse generator. Scope is set to 5TS/s ET.
3. Passing SPC and full self tests.
4. Power consumption on my AC watt meter. This scope would probably keep my small lab fairly warm in the winter.
5. My dog thinking that he should get a cut of the repair job and it should be paid with a Filet Mignon. Never-mind this lousy fake bone...
Jay

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Offline Someone

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #31 on: October 04, 2019, 10:03:20 pm »
Love the crack across the casing. Imagine returning a rental/company car with the bumper snapped in two, but hey its just some plastic box that looks like a computer no need to take care of it.
 

Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #32 on: October 05, 2019, 09:54:20 am »
Love the crack across the casing. Imagine returning a rental/company car with the bumper snapped in two, but hey its just some plastic box that looks like a computer no need to take care of it.

Those front bezels are really flimsy, and these scopes are HEAVY! Pretty sure this happened during shipping.
Jay

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Offline nctnico

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #33 on: October 05, 2019, 11:24:36 am »
So the fuse is blown on the inverter. Probably a pre-existing condition that the customer did not disclose.
NEC 121PW181
https://www.newark.com/nec/121pw181/inverter-5ma-lcd-module/dp/01P4251?CMP=AFC-SF-OEM

No real stock from reputable vendors.
I'll order a fuse and see if it opens up again. It's 3.5mm in size. Datasheet says: rating 1A, fusing current 2A.
Part # CCP2E20HTTE. Annoying datasheet does not allow copy-and-paste.

There's some inverters available on Ebay. The customer is in a rush (I think they are military) so I've been buying parts with over-night shipping.
Might just buy an inverter as well, JIC.
The cause could be worn CCFL tubes in the display. So I'd replace them to make sure. Otherwise chances are high you'll see the oscilloscope back on your doorstep for a free repair.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Jwalling

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #34 on: October 05, 2019, 02:12:05 pm »
So the fuse is blown on the inverter. Probably a pre-existing condition that the customer did not disclose.
NEC 121PW181
https://www.newark.com/nec/121pw181/inverter-5ma-lcd-module/dp/01P4251?CMP=AFC-SF-OEM

No real stock from reputable vendors.
I'll order a fuse and see if it opens up again. It's 3.5mm in size. Datasheet says: rating 1A, fusing current 2A.
Part # CCP2E20HTTE. Annoying datasheet does not allow copy-and-paste.

There's some inverters available on Ebay. The customer is in a rush (I think they are military) so I've been buying parts with over-night shipping.
Might just buy an inverter as well, JIC.
The cause could be worn CCFL tubes in the display. So I'd replace them to make sure. Otherwise chances are high you'll see the oscilloscope back on your doorstep for a free repair.

IME, they usually get dimmer. This display is pretty bright, but I did pull them out to have a look at them. They were nice and white with no signs of  browning.
The customer said that it was working fine before the main failure.
Jay

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Offline nctnico

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #35 on: October 05, 2019, 03:09:27 pm »
Then it is weird the fuse has blown on the inverter.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline KE5FX

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Re: 16GHz Tek DSA71604C. What were they thinking?
« Reply #36 on: October 06, 2019, 12:13:55 am »
Agreed that this is an odd combination of failures, but why would worn CCFL tubes cause inverter fuses to blow?

This seems like a really nice scope, probably deserves an LED backlight upgrade.  (And an HD image backup, while you have it on your bench!)
 


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