Rohde & Schwarz SMIQ front glass replacement

[HalFoster]

I have a couple of these units - the '02 and '03 - and both have the yellowing around the edge of the display glass.  Does anyone have an information on replacing this?  AFAIK the existing glass is RF screened - is this available, or would just having a piece of standard glass cut to fit be an option?

Thanks,

Hal

[DaJMasta]

Is this the yellowing or the greenish crackle they sometimes get?  I don't know if I've specifically seen yellowing, but I know a lot of screens have had issues with greenish corrosion sort of looking stuff.


It certainly could be screened glass, but it may not have to be - the front section with the screen, front panel, and CPU are all in their own module, so they may be well enough shielded from the rest of the unit that it may not to require it.  Didn't take my SMIQ's front section apart when I still had it, so I can't help in that instance.

[eb4eqa]

Hi. It is actually a glass with a very fine wire mesh embedded. If you look at it under a microscope or a powerful loupe, you will find the greenish area is actually the wire mesh  rusting and creeping towards the center of the screen. finding a replacement is not easy or cheap. I once made a replacement with perpex sheet. It looked great and I did not face any kind of issues with RF going in or out of the instrument. Some people will cringe but do whatever works for you.

Regards,
Roberto

[HalFoster]

Thanks!  You are right, it is a greenish yellow.  I bought them both to resell since I have a couple HP's in my horde... uh, collection, that do what I need.  That being said, the joy of restoring test equipment is my "thing" and I really like to bring anything to the best condition feasible, whether kept or sold.  The keyword there being feasible of course.  I'll probably wind up replacing it - should be able to have glass cut to fit.

Thanks again,

Hal

[Radiosonde]

I think it could be possible to buy a CMD57 or CMD55 (100 Bucks) and use the glass from them.
The housing is pretty mucht the same and I thint that even the PSUs are compatible ie. the same.

Regards

[HalFoster]

Thank you! I replaced the glass in both units with standard glass, but would like to have a lot closer to OEM - especially in the '03.  It is in otherwise perfect shape and pretty much in spec as far as I can tell.  There is a local cal lab that will do a NIST with data on it for US $650 - not bad at all, especially since there is no shipping involved.   I'll probably sell them both since they are overkill for my personal use but I would like them to be as close to original as I can.

Thank you again!

Hal

[energy_hunter]

I suffered with the green corrosion on my SMIQ06B for years and the corrosion started to creep in far enough to get me to fix it. I ordered a new screen from Rohde & Schwarz. Cost was high at $390 plus shipping but it is EMI glass and it comes with the tape already on it for an easy fix. Use acetone to get the screen off of the metal frame. Now my machine looks nice. Part number is: 1036.4319.00, R&S Type: ERST.2 OP MESHSCH.EMI-CLARE 4

[strick]

Hi,
I just wanted to post this for anyone buying a SMIQ-03B or similar (probably any of the SMIQs).  I bought a SMIQ03B with the front glass discoloration due to the metal screen and was able to get a very good deal on a fully equipped SMIQ-03B. 
The guys in the forum earlier had mentioned replacing the defective screen with a new glass.  I took apart the front of the SMIQ to be able to measure the glass from the inside.  the glass was held in with 10 or more screws and a metal frame.  Once removed, I noticed that the glass was very thick and appeared to be de-laminating in the middle.  The posts indicated that the glass has a metal screen in the middle to preclude emissions.  I decided to try to separate the glass parts to see if I could separate the parts.  I wasn't worried about breaking the glass, as I could still measure the frame to get a new piece of glass to replace it.
Once I really started probing with a very thin X-acto knife, the parts started to separate and I probably got about 2 square inches of glass separated before the front glass part started to crack and break.  I discovered that the front part of the two-part glass was extremely thin (2 mm or so) while the back glass was much thicker (6-8 mm).  they are separated by a thin (<1mm) rubber/metal web membrane and glue.
It took a while, but after some time, I managed to fully remove all the front glass and the offending membrane from the rear glass, being very careful to slowly raise the membrane and thin glass from the rear glass.

Since the rear glass was the part in the frame, returning it to it's frame and assembling, gave me a nice clear screen, without the clouding around the edges that I had before.

I had some thoughts about why R&S would bother with a screen in the glass before I took the SMIQ apart, but I found that there is a thick metal panel at the rear of the front section (the controller) and another thinner metal piece between the circuit board and the LCD screen.  Thus, the only thing that can radiate from the glass is the LCD.  Very strange. Why would they worry about that?

Just thought I would share,
Strick

[Haenk]

Thus, the only thing that can radiate from the glass is the LCD.  Very strange. Why would they worry about that?

Because they do
There certainly is coming a lot of RF noise out of the display area, which is likely bad when developing/measuring RF stuff. So RFI/EMI-shielding is essential.
Have a look at this PDF:

https://www.researchgate.net/publication/3866331_EMC_analysis_of_an_18_LCD_monitor

[strick]

Ah thank you!  i figured that someone out there knew why and that R&S simply didn't do it for grins...

The study you referenced did state, in the conclusions, that the major source was not the LCD, but the electronics driving the LCD.  As I indicated, there is a metal shield between the electronics and the LCD itself.

However, I would wonder about the myriad of commercially purchased LCDs hooked up to computers that are are also probably in any lab space.  I suppose you can get computer LCDs with front shielding, but I imagine they are quite expensive...

My primary intent was simply to inform other enthusiasts who ended up with discolored screens (due to a manufacturing or design defect) on these obsolete machines.  I would certainly advise any advanced design lab or manufacturing facility to observe all the proper protocols and emissions standards.  They should be the ones to purchase a replacement glass from R&S at $350+ (more than I paid for my fully equipped SMIQ-03B).  Or, better yet, upgrade to a modern, more capable machine and sell the old guy to folks like me.  I certainly would have purchased a new, proper screen, if it were not my dime and it's only a hobby.  I actually did try to buy a front panel from a guy on GreedBay, but he had already removed it from the front panel.

  Do not think that your point is not well taken and I thank you for educating me!

I intend to see if I can measure the radiation from the screen and compare it to my TDS-5104B LCD and one or more of my LCD monitors in my lab and will post any results here for interested viewers.

Strick 

[richnormand]

"I intend to see if I can measure the radiation from the screen and compare it to my TDS-5104B LCD and one or more of my LCD monitors in my lab and will post any results here for interested viewers."

If the frequencies radiated are not too high using a regular ITO coated glass (available in bulk for cheap and easy to cut to size) might be a good option to replace the SMIQ glass then?
One would have to ground the ITO coating on the edges/corners to chassis ground to have a better shielding (silver paint).

Would depend a lot on the sheet resistance.
https://www.geomatec.com/products-and-solutions/electricity-control/anti-static-and-electromagnetic/emi-shield/

[strick]

Well, I took a look.  The only thing I have that might be suitable is an HP8591E that has a nominal noise floor of around -70dbm.  It can be reduced to about -85 dbm at narrow scans and reducing the floor.

I don't have a proper probe, so I tried two separate antennas.  One was a loop of wire attached to the center lead of a 50 ohm cable, the other was a similar cable with both leads wrapped around a plastic container about 2 in in diameter.  The leads were not attached.

The loop was more sensitive, so I'll give my results on it.

The baseline full 1.8 GHz scan showed only signals below 108 MHz in the ambient condition at -55dbm.  There were also signals down in the below 2Mhz region at lower levels (-60 dbm or so) which are probably AM broadcast signals, just like the 108 Mhz FM signal.

When I held the antenna about 3 inches from the front of the SMIQ glass, I saw a signals between 10 Mhz and 100Mhz at levels approaching -60 dbm.  So, there are signals coming out.

Then I tried my TDS5104B and saw similar spikes and activity between 10 and 100 MHz, but the level was a lower -65 dbm.  Very surprisingly, my cheap SCEPTRE computer monitor didn't show anything!  Maybe they do shield them better, somehow.

Then, finally, I just took my probe and ran it around the metal case of the SMIQ and I got the same signals of 10 - 100 Mhz as I put the probe within 3 inches, but the level was -50 dbm, or 10 dbm higher than outside the front glass.

My testing above is limited by my equipment and lack of a truly sensitive probe, but it appears that signals out the front are not particularly powerful.

Strick

[jdragoset]

These
https://www.ebay.com/itm/TEKTRONIX-Radio-Interference-Mesh-Filter-for-2235-2236-2213-2215-22xx-Scopes/163650941430
were standard on the military Tek 2235's but the civilian 22xx versions were just a clear implosion shield and a blue filter with no shielding

[strick]

thanks.  that's interesting- just wondering why the military would be concerned, unless it was to be used in a high EM environment like a flight deck.  I used to be a Navy pilot and every time the main search radar would sweep over the airplane (F-4 and F-14), you could hear the static in your headset.  Perhaps they were concerned about fixing things in the field with a lot of active signals.

thus, I can understand trying to keep signals out, but not so much for preventing emissions.  The only emissions sensitive stuff I know of is ordnance (especially guys like 5" Zunis or 2.75 rockets).  No way they would let you operate near those...

Perhaps the emissions from the scope could affect sensitive electronics in the numerous circuit cards that we had in the radar boxes.  I simply don't know.

I spend lots of time fixing TDS5-700 series as a hobby, but I've never come across a shielded CRT...

Strick

[jdragoset]

Based on the number of surplus scopes this fellow has for sale
https://www.ebay.com/itm/Tektronix-2235-Lot-of-72-AN-USM-488-100MHz-Oscilloscopes/292789061542?hash=item442b9687a6:g:BbMAAOSwEJlb0xly
I'm thinking they were widely spec'd in many military applications.
I also think military spec's had a lot to do with the very wide AC input (90-277 VAC, 48-440 Hz) for that generation of scope designs by tektronix.

[drhex]

Can confirm that the glass (and display!) from a CMD57 work - the frame is different though which gave me a scare. So keep the glass frame from the SMIQ if you want to go down this route.