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.

[hendorog]

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

It would be a good idea to double check that this is actually faulty before replacing it (which is not what I did!) - some of the normal behaviour of the 8753 makes it appear like the supercap is faulty. It's a bit of a pain to replace it and then find that nothing has changed...!

For example saving the instrument state doesn't save the calibration. I think the display settings are also lost and need to be saved and recalled using the option in the display menu.

[Howardlong]

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

It would be a good idea to double check that this is actually faulty before replacing it (which is not what I did!) - some of the normal behaviour of the 8753 makes it appear like the supercap is faulty. It's a bit of a pain to replace it and then find that nothing has changed...!

For example saving the instrument state doesn't save the calibration. I think the display settings are also lost and need to be saved and recalled using the option in the display menu.

Hmm, maybe it's simple operator error then. Those are the exact symptoms. So you need to recal and reset display settings each time you switch on... as I've been doing for the past 15 years, assuming that the battery was dead?

[hendorog]

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

It would be a good idea to double check that this is actually faulty before replacing it (which is not what I did!) - some of the normal behaviour of the 8753 makes it appear like the supercap is faulty. It's a bit of a pain to replace it and then find that nothing has changed...!

For example saving the instrument state doesn't save the calibration. I think the display settings are also lost and need to be saved and recalled using the option in the display menu.

Hmm, maybe it's simple operator error then. Those are the exact symptoms. So you need to recal and reset display settings each time you switch on... as I've been doing for the past 15 years, assuming that the battery was dead?

Thats correct, you probably already know about this, but you can get around the recal annoyance with a GPIB adapter and KE5FX's VNA util.
http://www.ke5fx.com/gpib/readme.htm#VNA

[Howardlong]

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

It would be a good idea to double check that this is actually faulty before replacing it (which is not what I did!) - some of the normal behaviour of the 8753 makes it appear like the supercap is faulty. It's a bit of a pain to replace it and then find that nothing has changed...!

For example saving the instrument state doesn't save the calibration. I think the display settings are also lost and need to be saved and recalled using the option in the display menu.

Hmm, maybe it's simple operator error then. Those are the exact symptoms. So you need to recal and reset display settings each time you switch on... as I've been doing for the past 15 years, assuming that the battery was dead?

Thats correct, you probably already know about this, but you can get around the recal annoyance with a GPIB adapter and KE5FX's VNA util.
http://www.ke5fx.com/gpib/readme.htm#VNA

Pretty much all I use that GPIB toolkit for is screen shots, I should try harder!

Thanks for the tip.

[TiN]

Got the reinforcements today:



Color LCD kit NewScope-9 from Simmconn Labs.

Money shot on controller board:



Good old Spartan-6 FPGA, die of memory, Winbond SPI Flash ROM with bitstream, few 384 buffers and 3.3 Vreg. It takes digital data from 8753A display bus and translates it into LVDS stream for TFT panel.
Of course there is more to it than just interface converter, as even original CRT module in HP 8753's has own VRAM, processor, chargen and vector to raster engine.

Kit comes with nice industrial grade panel and crappy CCFL HV inverter. That dodgy Jicon capacitor there has to go.



Now need to find time to install it into unit and see how it goes. Bit not easy, as whole VNA is teared apart and have it's guts spread all over the apartment  .

[TheSteve]

Ditch the entire CCFL and go to LED's.

[TiN]

Yey, it's alive.



Well, sorta...

Unknown-condition 8753A with rusty boards.. Check..
LCD kit working with color... Check...
Replacement HP N-SMA connectors 4pcs.... nope..200$USD?
Hardware and knowledge to test functionality of VNA....nope....200-1000$ for attenuators, couplers, loads?
S-parameter test kit?....nope....1500$
Calibration kit for Type N up to 3G...nope....500$?

Uh-oh...
I'd rather get another rusty 3458A then for time being! 

[hendorog]

Yey, it's alive.

Awesome - and its better than new cos its in colour!

Right, here we go, VNA on a budget is my new speciality

Replacement HP N-SMA connectors 4pcs.... nope..200$USD?

These might be another option - i.e. dump N and use SMA instead. I would have saved a lot of money in adapters if everything was SMA!

http://www.ebay.com/itm/HP-Agilent-Bulkhead-Connector-3-5mm-26-5-GHz-/381775153701?hash=item58e3928a25:g:u8gAAOSw37tWBFtm

S-parameter test kit?....nope....1500$

T/R test set is a much cheaper option here, the only downside is you have to reverse the DUT yourself. There are a couple of upsides too - more flexibility and very slightly better specs due to a simpler signal path. They go for around $200-$300 normally. You want the 50 ohm 85044A model not the 75 ohm 85044B.
Here is a really cheap one which is a bit beaten up ($75):

http://www.ebay.com/itm/HEWLETT-PACKARD-85044A-TRANSMISSION-REFLECTION-SET-300KHZ-3-0GHZ-/201693688646?hash=item2ef5e17346:g:GxUAAOSwMHdXRfqb

You need a precision adapter for the test port, which are not that cheap. If you use a cheap adapter instead on the test port then the adapter will become the limiting factor in the (uncorrected) directivity of the system. The adapters and cables for the other ports are not as critical.

Building a T/R test set is another option and is pretty straightforward. The uncorrected directivity isn't as good - but an OSL calibration corrects for directivity. I've got a couple of PCBs I can send you that you just need to plop connectors and some parts on.

Hardware and knowledge to test functionality of VNA....nope....200-1000$ for attenuators, couplers, loads?

Splitters are easy to build, couplers are harder to build but are available on ebay pretty cheap. I have a couple that have excellent performance considering they were never designed to be used in a VNA!

Get some SMA terminators, attenuators and test cables from eBay. Reasonable quality stuff is cheap enough.

Calibration kit for Type N up to 3G...nope....500$?

I've got one of these ($71):
http://www.sdr-kits.net/Webshop/products.php?50&cPath=5

[Howardlong]

Definitely agree with standardising on SMA rather than N.

I have the 75 ohm T/R test set rather than the S parameter test set, and use it with a minimum loss pad to convert it to 50 ohms with some loss of dynamic range.

Don't get too uptight about super expensive cables, the unit will cal out any reasonable cable losses and minor mismatches.

The key is to have it calibrated at the DUT, and that often means making your own cal kit and test jigs if you're unit testing a subsection of a PCB. Having a proper cal kit though is pretty much essential to ensure that the VNA is working correctly as well as testing those devices which happen to terminate in your cal kit's connectors.

[TiN]

HP-Agilent-Bulkhead-Connector-3-5mm

Ordered 4pcs.
It's not an SMA however, it's 3.5mm
So I think I'll still need to get 3.5mm-N cables in future to connect regular N-type test set.

[hendorog]

HP-Agilent-Bulkhead-Connector-3-5mm

Ordered 4pcs.
It's not an SMA however, it's 3.5mm
So I think I'll still need to get 3.5mm-N cables in future to connect regular N-type test set.

They are compatible with SMA. I was just too lazy to type 3.5mm (now look what you made me do
http://na.support.keysight.com/pna/connectorcare/What_mates_with_what.htm

The other option is to use SMA-N adapters when you get the test set. At least you will only need 3 (or 4) now

I have the 75 ohm T/R test set rather than the S parameter test set, and use it with a minimum loss pad to convert it to 50 ohms with some loss of dynamic range.

Do you need 75 ohm N connectors for these with the larger centre pin? Also, do they top out at the 2GHz spec or can you use them a bit  beyond that? I've observed that the A model doesn't go much beyond its 3GHz spec.

[Howardlong]

I have the 75 ohm T/R test set rather than the S parameter test set, and use it with a minimum loss pad to convert it to 50 ohms with some loss of dynamic range.

Do you need 75 ohm N connectors for these with the larger centre pin? Also, do they top out at the 2GHz spec or can you use them a bit  beyond that? I've observed that the A model doesn't go much beyond its 3GHz spec.

No need for 75 ohm N connectors other than the one that's part of the 75 to 50 ohm minimum loss pad connected to the test set. Everything else is 50 ohms. I leave the MLP permanently connected to avoid self-inflicted operator error. You do lose 5 or 6dB of dynamic range as a result of using the MLP. There is nothing practically to stop you running the 75 ohm TR test set to 3GHz, and I've never noticed any particular problem in doing exactly that.

The 75 ohm test set came with my 8753A when I bought it around 2000, and I never bothered to change it.

[orin]

Yey, it's alive.



Well, sorta...

Unknown-condition 8753A with rusty boards.. Check..
LCD kit working with color... Check...
Replacement HP N-SMA connectors 4pcs.... nope..200$USD?
Hardware and knowledge to test functionality of VNA....nope....200-1000$ for attenuators, couplers, loads?
S-parameter test kit?....nope....1500$
Calibration kit for Type N up to 3G...nope....500$?

Uh-oh...
I'd rather get another rusty 3458A then for time being! 

I got quite a long way with an 8753C with these and a few adapters.

The couplers came from ebay, the splitter and attenuator from Mini Circuits directly, but I'd be surprised if you couldn't find them on ebay for less.  The couplers are only rated to 2GHz - I don't recall how well they did to 3GHz.  If I get a chance, I'll do an S11 calibration and look at the reported directivity.

To do the adjustments, you'll need the proper 11667A splitter, 8482A power sensor and 436A or 438A power meter... it starts getting expensive!  436As are cheap enough, but good luck finding an 8482A that works.

Having said that, as long as you didn't mix up the samplers, the adjustments saved in the EEPROM are probably OK as long as you do a user calibration with a good cal kit.

I was thinking of building up my own test set, but then an 85046A came up on ebay that I got for $350.  Port 1 fails the directivity test, but I can replace the bridge with one from an 85044A that I got for $120.

[TiN]

Okay I won, that HP 85044A and it's shipped. Shipping is 92$, while box itself 75$  .

Also 3.5mm bulkhead connectors arrived. Two are decent shape, I'd say 5- and two other are okay 4). Should be good enough for 3GHz VNA, as these rated 26.5Gig originally .
Will post macro photos later.

However I don't have suitable cables yet.

[hendorog]

Okay I won, that HP 85044A and it's shipped. Shipping is 92$, while box itself 75$  .

Also 3.5mm bulkhead connectors arrived. Two are decent shape, I'd say 5- and two other are okay 4). Should be good enough for 3GHz VNA, as these rated 26.5Gig originally .
Will post macro photos later.

However I don't have suitable cables yet.

Heh, welcome to the shipping company shareholders club.

If you can cope with having the test set directly in front of the VNA then these jumpers look pretty good:
http://www.ebay.com/itm/MARCONI-MICROWAVE-12cm-SMA-MALE-to-SMA-MALE-COAXIAL-LEAD-/351862994501?hash=item51ecab3645:g:jo8AAOSw8gVX8lpj

[TiN]

Well, the HP 85044A test set still has N-type ports. And that pesky APC7...

Oh well...

Promised photos of connectors. I'd appreciate if someone knows their original HP/Agilent part-number.



I bought 4pcs. N-SMA on the right is original from 8753A.



Two connectors are decent shape, two other bit worse. But nothing too bad.

Close-up of inner collet:



"Air" isolator, clearly visible by backlit photo on the right. Of course it's not air in full meaning of the word, but most of gap space is empty, hold just by the transparent plastic spacer.

To actually install them into 8753A's frame, some metal work would be required, as new connectors have only one notch on threaded mount, while old N-SMA had two notches on both sides.



I'll just mill excessive metal on the frame with Proxxon

And everything would look somehow like this:



Why all this trouble? Here are macro of original N-type ports:



Probably not so bad as most VNA-nuts would say to me, but I don't like that crud and rust on collets and housings. And you can see dents on the front outer shell, likely due to physical drop impact. All GHz's will run away 
Hopefully this would be enough to get something going, once I receive that 85044A. I'll get some cheapo N-SMA cables, and maybe APC7 to SMA or N adapter.

[vtp]

Probably not so bad as most VNA-nuts would say to me, but I don't like that crud and rust on collets and housings. And you can see dents on the front outer shell, likely due to physical drop impact. All GHz's will run away

OK, I will be then the first to say that those do not look too bad. You do know that the connectors can be disassembled completely, even the inner collet visible on your picture can be removed from the dielectric support? Would be a lot easier to clean those disassembled.

EDIT: If you do not want to clean those N-SMA connector blocks they are readily available for example on epray. The same bulkhead adapter has been used in a huge number of HP/Agilent instruments.

As for standardizing for SMA I'd rather use N connectors on instruments and then convert to SMA or similar with a good quality adapter. VNA needs to be calibrated anyway at the end of the connecting cable or adapter for measurements.

N lasts pretty much forever, SMA not so well at all. And APC3.5 is really easy to destroy with sub-standard SMA connector - all it needs is to have the center pin on male SMA connector to protrude too much (think of cheap chinese cables and adapters) and the APC3.5 center collet is a tiny flower after one insertion/removal cycle.

As for calibration kit, I would suggest brand new from any manufacturer that comes with actual coefficient data. I bought one "good" used 85033D from a cal lab and it was a complete disaster on what comes to female standards that get used the most. For the sake of peace of mind, I have a brand new 85033E from Keysight now.

[hendorog]

There are also these SMA-N if you choose to stick to the original:
http://www.ebay.com/itm/272427568928?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I'm just using reasonable SMA-SMA cables and a lot of cheap SMA-N adapters on mine. The adapters are a risk but I couldn't find decent matching N-N cables or N-SMA cables at a good price.

You will want a precision APC-7 adapter though, otherwise the nice directivity of the 85044A is degraded by the reflections from the adapter. The one I have is this one (same seller):
http://www.ebay.com/itm/7mm-to-SMA-f-Adaptor-OMNI-SPECTRA-OSM-2082-2700-00-/252575012486?hash=item3acea4d686:g:T20AAOSwbsBXiy9z

The first one I received had been dropped and had a 'flat spot' on the SMA connector which affected the return loss. The seller sent me another one FOC which is good.

[TheSteve]

Came across a really cheap 8753A today, so I am joining the club!

[Theboel]

if any one has 8753 family with whatever ugly looking condition and willing to send it to overseas  please let me know

[TiN]

Be careful, I'm this close to accept your wishes . Just looking at RF cables, calibration kits and APC7 or test set prices make me sick already...

[Theboel]

TiN I understand it very well and I watching my messages box very impatient   
 

[TheSteve]

Mine may be for sale at some point. Assuming it works or I can get it working I will be on the lookout for an affordable test set and the 4 jumper cables. Overseas shipping would be expensive but I do have access to a pretty heavily discounted UPS service.
I'd like the LCD upgrade for it but that is already twice what I paid for the 8753A including shipping. I already have an 8714C to compare it to so it should be a fun project either way.

[Nemo1956]

I have a 8753C where the tube is going flat now and very dark. So where did you get this LCD display?
Is it a simple up grade where can I find out about this please.
Thanks.

Paul

[TiN]

Welcome, Nemo.

All info was linked in my article , LCD kit was bought directly from Simmconn labs, model NewScope-9. It was quick and easy deal.

[TheSteve]

I have an 8753A as well. Based on the condition I don't think it has had that much use in its 30+ years. Guess it might need new caps. Now to find a test set for cheap to match the analyzer.

edit - decided to sell it.

[Howardlong]

I'm not convinced you'll need to re-cap, remember that the dodgy cap crisis happened after these beasts where manufactured.

The main failure point of these is the CRT display section where the display goes mushy. I'm not sure if this is just age or the amount of use they've seen. Mine got increasingly bad to the extent where it was getting very irritating, I had to adjust the display unit pots almost every time I powered it up, although it was fine when I bought it in 2001. Bearing in mind I only switch it on for a total of an hour or so a month on average, I'd say it's age rather than use. Newscope came to the rescue, and while it's not a cheap solution it breathes new life into the unit.