Repair : HP 8753A Network Analyzer

[TiN]

This is final 3rd part of Sonix's gear, and most interesting for me perhaps.

Everything came very badly packaged, heavy gear just tossed into cardboard boxes, with zero protection:



Result is as expected:



Protective glass screen is cracked and chipped. There are some dents on covers as well.



It's pure luck that CRT is not destroyed and thing actually does power on.



I never ever had network analyzers, nor used any, so at this moment I barely have any idea how these instruments work, leave alone how to use it or test it. The only RF-ish gear I have is 4GHz Tektronix, and few 10MHz Rubidium and GPSDO standards. Any ideas where to start? Books and articles how to use NA for newbies are welcome, please. 

I found LCD kit for 8753A, which is about 450$. I'd consider getting it after get initial repairs done and get confidence that unit is working properly.

[hendorog]

Haha, snap - Last night I purchased this wrecked 8753C...
http://www.ebay.com/itm/HP-Agilent-Network-Analyzer-No-Frame-No-Power-As-Is-/252411867849?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=wEiNpJ6q0gpoS313Zzj%252BbBkVaqY%253D&orig_cvip=true&rt=nc

...so I was looking for service manuals - and found this one for your model:
http://www.hparchive.com/Manuals/HP-8753A-Manual-Service.pdf

Disclaimer: As I don't have on the below is just based on reading and experimentation on the bench. There are plenty of others here who are more knowledgeable and with direct experience - and who will chime in I am sure

A calibration kit is needed. The VNA essentially compares the DUT to the calibration so the measurements are only as accurate as the calibration.
The original HP parts are very expensive even on eBay, so here are some cheaper options in order of quality:
* DIY: http://www.qsl.net/in3otd/electronics/VNA_calkit/SMA_female.html
* Cal kit for a cheaper VNA: http://sdr-kits.net/VNWA/RosenbergerCalKit.pdf
* Third party Cal kit: http://www.kirkbymicrowave.co.uk/

These are supposed to be used with a 'Test set', which is another expensive item.


Edit: There are also T/R test sets which are cheaper:
http://www.keysight.com/en/pd-1000002007%3Aepsg%3Apro-pn-85044A/transmission-reflection-test-set-300-khz-3-ghz?cc=US&lc=eng

I believe you can DIY a test set using a splitter and do S21 measurements of two port devices like filters. You are measuring the magnitude and phase of what goes through the DUT - e.g. in this listing:
http://www.ebay.com/itm/HP-8753C-300KHz-3GHz-Network-Analyzer-options-006-Channel-R-splitter-/281981997151?hash=item41a76fd05f:g:50EAAOSwqu9U7YL1

If you add a directional coupler or a bridge then you can also measure S11 - you are measuring the reflection from the device.

Certain test sets have a frequency doubler in them which extends the range of the signal source to 6GHz. Those test sets are very expensive on ebay.
Only a software key required on the VNA itself to extend the receivers to support this on the A, B, and C models. [Edit: The A model doesn't allow upgrading to 6GHz with a key]

There is a forum here were the original designer of these VNA'a pops up from time to time:
https://community.keysight.com/community/discussion-forums/network-analyzers/content?filterID=contentstatus%5Bpublished%5D~category%5Bgeneral-use%5D&query=8753

There are many app notes from HP which will help you get started, e.g.:
http://www.keysight.com/upload/cmc_upload/All/BTB_Network_2005-1.pdf

So where to start - I would start by making a simple cal kit and a resistive splitter with SMA parts as per the above web page. Then you can start to learn how it works by using it

[joeqsmith]

Both nice scores! 

[BFX]

This is final 3rd part of Sonix's gear, and most interesting for me perhaps.

Everything came very badly packaged, heavy gear just tossed into cardboard boxes, with zero protection:



Result is as expected:



Protective glass screen is cracked and chipped. There are some dents on covers as well.



It's pure luck that CRT is not destroyed and thing actually does power on.



I never ever had network analyzers, nor used any, so at this moment I barely have any idea how these instruments work, leave alone how to use it or test it. The only RF-ish gear I have is 4GHz Tektronix, and few 10MHz Rubidium and GPSDO standards. Any ideas where to start? Books and articles how to use NA for newbies are welcome, please. 

I found LCD kit for 8753A, which is about 450$. I'd consider getting it after get initial repairs done and get confidence that unit is working properly.

I hope you get refund for this crappy packed and broken unit. 

[acbern]

The first thing you may wish to check is if the generator is working properly. They had a hybrid based gen and quite often the output amp section fails. While there are theoretically MMICs out there that can be put in place, it is a very painfull job and especially at the low end it is hard to get a sufficiently high high signal level (guess how I know). Working hybrids are not available, you better then buy a new VNA. A first check may be done with a loopback cable. If that looks good, you are probably fine. If not, there may still be other issues, but most likely it is the amp.

[TimFox]

For a quick test, you need to run the output signal back into the reference input (best done with a resistive splitter) and also (maybe through an attenuator or similar) into A or B input and see if the "A/R" mode makes sense.

[TerraHertz]

Result is as expected:

That is SO sad, infuriating and disappointing. I assume when you bought, it wasn't wrecked like that?
Whhhhy can't people pack these precious instruments sanely? This should be posted in the 'poor packing' thread. With the seller ID.
You should demand at least a 50% refund, probably more. Hope you get it.

I never ever had network analyzers, nor used any, so at this moment I barely have any idea how these instruments work, leave alone how to use it or test it. The only RF-ish gear I have is 4GHz Tektronix, and few 10MHz Rubidium and GPSDO standards. Any ideas where to start? Books and articles how to use NA for newbies are welcome, please. 

This is exactly my state too, except I can't even afford to buy a wrecked one. Very little RF knowledge, never even touched a functional VNA. Back when I was working and could afford (some) things, I bought basic old-style RF test gear, thinking I'd work my way up from the basics. Things like slotted lines, power meters, RF gens, HP 8405A, 8410B, etc. Still haven't had the 'freedom from life interrupts' time needed for that, sigh.
One book I found:
  Electronic applications of the Smith Chart - in waveguide, circuit and component analysis. By Phillip H Smith. Pub 1969.
  http://www.abebooks.com/servlet/SearchResults?an=smith&sts=t&tn=Electronic+applications+of+the+Smith+Chart

Others:
  Microwave theory and measurements. By Engineering staff of the microwave division, Hewlett-Packard company. Prentice Hall 1962.

  HP Application note 117-1. Microwave Network Analyzer applications. June 1970.
  HP App note 91. How vector measurements expand design capabilities  1 to 1000MHz. (Using the HP 8405A vector voltmeter)
  HP App note 92. Network analysis at microwave frequencies.  (Using HP 8410A network analyzer)

I like old books, they are generally so much more practical than modern texts.

Edit: there is also this thread: https://www.eevblog.com/forum/testgear/vna-adice/

[TiN]

Thanks for infos, I'll study them.
Seller was local, and deal was offline, so no much refund stuff possible. It was 300$, so not that horrible.
And if unit gets to a point of successful repair and full operation, LCD kit upgrade would be the right way.
It's still technically sonicyang's device, I'm just a helping hand  .

[TerraHertz]

Thanks for infos, I'll study them.
Seller was local, and deal was offline, so no much refund stuff possible. It was 300$, so not that horrible.
And if unit gets to a point of successful repair and full operation, LCD kit upgrade would be the right way.
It's still technically sonicyang's device, I'm just a helping hand  .

Ouch, that's just a trail of woe.
Is the reason you didn't go and pick it up yourself, related to that nice slim bicycle wheel in the pic?
Anyway, lesson: if the tech-thing is local and delicate, go pick it up yourself. Where the range of 'local' depends on the nature of the item. I once drove Sydney to Melbourne to pick something up. No way was I going to let a courier get their hands on it.

My depressing news for today: Setting up to have my car rego check, I found out the guy who runs my favorite local garage lost an eye in a work accident recently. He's a great guy, I feel very sad. Sucks. He'd recently sold the land block his old garage was on, for a huge amount, bought a much bigger industrial site not far away, did a lot of nice renovations and now has a bigger business with spiffy buildings and vastly more workshop space... then this.


Edit:
  http://www.hpmemoryproject.org/an/pdf/an_117-1.pdf    12MB. Quality better than _most_ scans, but still crap. Sigh.
  http://www.hpmemoryproject.org/an/pdf/an_91.pdf   3.7MB
  http://www.hpmemoryproject.org/an/pdf/an_92.pdf   2.9MB

Actually, if you prefer physical paper books, I have a spare copy of an_117-1. If you want it, PM me your address. Not sure what the postage would be; if more than a few dollars you'd have to pay it. (I'm very poor.) But I think the pdf will do you, especially since you don't strike me as a collector of old things.

[razberik]

Why  he sent it like this ? I don't understand.

[Howardlong]

I still have the 8753A I bought 15 years ago, the only repair I've done to it is to do the Newscope LCD screen as the CRT was starting to become troublesome, which I firmly recommend, it takes decades off the unit.

As previoulsy noted, this VNA is pretty much useless without a test set, either S-parameter or T/R.

I still use a 75 ohm T/R test set with a minimum loss pad, so I lose a few dB of dynamic range but it's been fine for my purposes, which is measuring and tweaking filters, and matching them and antennas.

You will need a decent cal kit too. Like the test set, the VNA is useless without one.

[TiN]

More rusty boards, yey!















Anyone has PDF-version of HP 1349A/D display unit operation/service manual ? I think that's where I'll start repairs, as it's focus was all over the joint, and now no display on CRT at all.
I'll buy one from Artek Manuals later anyway (just for sake of supporting great site  ) but can't wait to wreck something more in this rusty thing, while 3458A logging resistors...

TerraHertz
Ouch, sad story there..

I have a spare copy of an_117-1. *snip*.. especially since you don't strike me as a collector of old things.

PDF will do fine for me, as I'm short on storage space for stuff, thanks. As of old things...8pcs 20+ year old DMMs? Check. 30-year old volt-nut pieces? Check. 35-year old wire-wound precision resistors? Check... I'm not so sure anymore.

[TiN]

More autopsy, as my niece said, helping me pull the boards and sort nuts  .

PSU in own shielded cage with some neat metal brushes to faces to keep EMI out of RF gear..



Ugly dirty 24V fan:



Front panel





Damaged Amphenol 131-445 N-3.5mm connectors:



There is some rust on inner center terminals too, so I feel those need to source replacement..

RF source



Sampler and pulse boards rust:



Any idea how to clean all those RF parts? :\ I'd assume spraying everything with IPA and brushing would not be good idea for RF circuitry. How about ultrasound bath?

Bonus shot, pulser output diode?

[sonicyang]

Bump into some problems.

Boards handling RF stuff are very dusty and the metal part of chip/transistors are rusted.
We are concerned about the extant of stray capacitance.

Brushing with Alcohol don't seems working. As some location are not reachable with a brush.

Anyone have a good method to proper clean those off the board?
Leaving nothing and make it live for another 10 years?

[KE5FX]

Just blow the dust off with compressed air.  Those boards appear to be in pretty reasonable shape.

[PA0PBZ]

Wow, a fan with teeth, you don't want your finger in there when it turns 

[TerraHertz]

Wow, a fan with teeth, you don't want your finger in there when it turns 

Actually that's the blade trailing edge, so it wouldn't bite.
The serrations are there to prevent coherent air turbulence over the tail edge, that is a source of a lot of the fan noise. That's why they are only on the outer edge, where the blade velocity is highest. Serrated blades like these are pretty common.

[TiN]

Peroxide in play again, to whiten key caps

.

Worked nice.

[cncjerry]

hey TiN, tell me more about peroxide used for cleaning.  That's a new one for me.

[Vgkid]

Pretty cool to see the guard traces on the analog board. That one board with the transistors looks extra crusty.

[TiN]

hey TiN, tell me more about peroxide used for cleaning.  That's a new one for me.

No problems, I made a guide, covering this simple method.

Vgkid

I'm still puzzled how exactly to clean those RF boards from rust 

[razberik]

Yeah, I am curious too. I think RF parts are more important.
I wouldn't white buttons, just leave them as they are. Of course yours look nice.

[hendorog]

Amazing difference on the colour of the keys ! The power button on mine has the same yellow colour, thanks for the tip off

[TiN]

Okay, sorry for long no activity, was carried away by other volt-nut related projects for a while.

But it's not forgotten, as I just took a brave pill and ordered Newscope-9 LCD kit for this poor 8753A, hoping it would be worthy and instrument would be repairable.
Decided not to bother with CRO module repairs and adjustments, call it a scare from those kV-marks all over it. I work in my homelab alone, so there would be noone nearby to provide medical help from HV zap  .

[Howardlong]

Okay, sorry for long no activity, was carried away by other volt-nut related projects for a while.

But it's not forgotten, as I just took a brave pill and ordered Newscope-9 LCD kit for this poor 8753A, hoping it would be worthy and instrument would be repairable.
Decided not to bother with CRO module repairs and adjustments, call it a scare from those kV-marks all over it. I work in my homelab alone, so there would be noone nearby to provide medical help from HV zap  .

Good choice, anecdotally the CRO on these is by far the weakest link, whereas the rest of it refuses to lie down and die. My CRO assembly still works but needed almost continual adjustment and fiddling in recent years: I found replacing with the NewScope 9 was a great update, and it took many years off it in aesthetic terms.

Now I just need to fix the supercap/battery backup on day.