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Old 10th Mar 2021, 2:31 pm   #101
Matt kd4pbs
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Default Re: Spectrum Analyser TR4172

After adding the resistors, the VSWR ended up around 1.6:1 at 2.05GHz. Unfortunately, the iron melted a bit of the end of the input strip, so it's a couple mm shorter now than when I started. If anyone needs to know in the future, the iron was set to ~345C and it melted the strip. I knocked it down to 300 and worked quickly to do what I could do. A 0603 size resistor worked fine. I saw about 1.3:1 when I just pressed the resistor onto the trace. In the process of it all, part of the square loop came detached from the board, and I had to do the same glue technique to fix it. That whole input filter coupler is so fragile that I don't want to touch it again. I probably screwed it up a bit from doing this. I wish I could just scrap it and make or find a new filter, but I have no way of making this kind of a circuit board and chances of finding a replacement are of course quite unlikely.
Either tonight or tomorrow I will attempt to fix the regulator board, and hopefully it all will still work. It's getting quite ugly, as I just don't have the technique and equipment required for such intricate work. The board itself has such high thermal conductivity that it makes it difficult to find a balance between the temperature that won't melt the trace and a temperature that will be hot enough to still melt solder after the heat gets wicked from the tip from the board itself. It's just down right hateful.
I hope that all of this helps someone in the future looking to fix their sick TR4172.
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Matt
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Old 10th Mar 2021, 5:09 pm   #102
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Smile Re: Spectrum Analyser TR4172

Jeremy & Matt, mine is alive ! Finally I did the substrate interconnection repair (3 of 4) at home and it went well. What I have seen is that there is also an issue with the gold layer. In my case there is a straight connection which gives stress. I did not change the connection (afraid to damage the gold to much) and only re-solder it. I had to touch the gold traces but they did not fall apart. In my case the gold is not as fragile as described by you (maybe improved/newer series). The measured gain of the IF1 is about 0 dB at 2.05 GHz with a slight negative slope. I will measure it at a later moment at work with a real VNA. So, conclusion for my IF1 gain loss of the TR4172:
- Broken PNP of the bias circuit which is replaced by a BC857B
- Three interconnections between the substates were open

When I got this analyser it already had a gain loss of 10 dB and a few weeks ago (did not use it for a long time) no gain at all. I hope that the 10 dB gain loss is also solved now, we will see. Jeremy, thank you for your help and the schematic of the bias circuit, which you already had figured out, was very helpful to me .

Regards, Lex
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Old 10th Mar 2021, 6:48 pm   #103
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Default Re: Spectrum Analyser TR4172

This is great news, Lex! I am glad that this was indeed the source of the deafness. I still hold out hope for mine as well, but in the meantime, I'm preparing for plan B; a separate cavity filter input with circulator, and a separate amp. I need to look at my parts box, but I might already have the filter and I know I have a circulator. Of course, the circulator being a non-linear device, I don't know how well it would work in front of all of this. As such, plan C would have me put a more typical directional coupler before and after the filter instead, just like the existing filter.
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Old 11th Mar 2021, 12:19 am   #104
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Default Re: Spectrum Analyser TR4172

Yes, that is good news from Lex! Hopefully it will now perform closer to the factory specs. I had a rummage here and managed to find the little Operator's Guide for the TR4172. It has a date of 1986 on the back and this was supplied to me with the analyser back in 1990.

Manual Number 4172-OGE-602D

Here's an old image of the "TR4172 Spectrum Analyzer Operator's Guide". It is really falling apart so I keep it stashed away in a protective bag these days. I don't think there's anything in it that isn't in the full sized manual but back when I first used this analyser this handbook was all I had. It needs a new binder thing down the side and some of the pages are breaking away from the binder.

Do either of you have the impedance measurement option fitted? This analyser has a special party trick where it can act as a vector network analyser when an external bridge is fitted and it has the impedance measurement option fitted internally. Both of mine have this option although I've hardly ever used it.
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Old 11th Mar 2021, 1:11 am   #105
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Default Re: Spectrum Analyser TR4172

When I first lugged this home, I was hoping it did, as this was before I had the 8753D. It does not, unfortunately. It does measure phase, but that's it. I don't even know if the impedance measuring option was available when this one was made since it is TR branded. I wouldn't be surprised if this was a first-year model. From what I've read about your opinion of the impedance measurement option though, it appears to not be any great loss to not have it.
I did receive both of the transistors today, but unfortunately the 2SC2150 is NOT an X-package as the auction described. Hopefully this won't matter in that now that I can get a test lead on the amp transistor, it appears good.
For my plan B, I located and measured my cavity filter at 2.05GHz:
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I even noticed that I had a pretty high gain little amp - I'm thinking 25-40 dB - that I had forgotten about which followed this filter, so if I really need to go that route, I think I have a solid plan B.

Edit: I forgot to ask, do you have a scanner? It might be worthwhile to preserve that manual digitally.
73,
Matt
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Old 11th Mar 2021, 1:45 am   #106
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Default Re: Spectrum Analyser TR4172

Check to see if the manual is already on the BAMA website. If it isn't they'd no doubt like a copy if you scan yours.

David
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Old 11th Mar 2021, 10:36 am   #107
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Sadly I don't have a scanner. I think nearly all of the contents are in the main manual. The handbook does explain some of the more obscure hidden features such as the ability to measure and display electric field intensity in dBuV/m with a suitable dipole antenna. There's also a double shift key feature to display a smith chart in impedance mode. It can also do EMC measurements and there is a 7Hz RBW filter function in the SHIFT key menu. It was also very good at measuring crystals and crystal filters and could also measure the group delay of filters.

Probably the most niggly aspect of this analyser is getting display plots from it. My analyser has the GPIB controller option fitted so this clashes with external plotters like the classic HP7470A. For many years at work it was thought the analyser's GPIB interface was faulty. However, there is a key sequence to press to bypass this 'controller' feature. This means the analyser can produce plots using a plotter or the KE5FX GPIB toolkit. KE5FX produced an emulator for the HP 7470A so plots can be dumped to a PC. This runs quite slow because the plotter was slow.

One other neat feature of this analyser is that it allows full access to internal memory adresses via GPIB so it is possible to grab the display trace data dynamically. The display is stored as 1000 x 1000 datapoints so it is possible to create high resolution plots using a PC and this is also much faster. I managed to get about 5 full resolution plots a second via GPIB. This is the equivalent resolution of a modern 1000 x 1000 digital display.
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Old 11th Mar 2021, 1:20 pm   #108
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Default Re: Spectrum Analyser TR4172

Quote:
Originally Posted by G0HZU_JMR View Post
The handbook does explain some of the more obscure hidden features such as the ability to measure and display electric field intensity in dBuV/m with a suitable dipole antenna.
That could be a useful function very shortly if you've seen the latest OFCOM message to radio amateurs? The thread on it is closed at the moment, waiting for the RSGB to publish their calculator spreadsheet and worked examples.

David
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Old 11th Mar 2021, 2:44 pm   #109
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Default Re: Spectrum Analyser TR4172

Those feature docs you mention would be very handy. I often use the KE5FX HPIB stuff, including the 7470A emulator; that's how I grabbed those 8753 plots. I also use his phase noise measurement tool with the 4172 and it works nicely. Being able to produce plots from it would be very nice as well, and I actually do have a genuine HP7550B that you don't want to get your fingers to close to if it's plotting... capable of at least 1,000 paper cuts per second.
Having a suitable dipole and being able to read uV/m would be handy in my field of work. It seems that I remember being able to use 7Hz by just inputting it directly though - perhaps that's a change they did in later firmwares? And I think the data for the smith chart is missing with mine - I seem to remember trying the key combo to get it in the past and it simply did nothing... likely due to not having the impedance option.
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Matt
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Old 11th Mar 2021, 3:02 pm   #110
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Default Re: Spectrum Analyser TR4172

If you can run the KE5FX phase noise utility I think you may be able to run the plotter emulator as well. My analyser has various options fitted and one of them fights against any attempt to control the analyser remotely via GPIB. Yours probably doesn't have this option.

See below for the electric field intensity mode. This might also be in the main manual but I couldn't spot it easily. I'm afraid it won't be easy to read the text because the forum limits the image size to about 50kb. Give me some time and I'll charge up an old camera and take a decent image with a tripod and upload it somewhere else.

The smith chart mode isn't really worth having these days because a nanoVNA will outperform the analyser in this mode up to maybe 300MHz. Also, the smith chart mode can put a very intense dot on the CRT and there is the risk of screen burn. I think I've only used this mode three or four times in 30 years.
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Old 11th Mar 2021, 3:21 pm   #111
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Default Re: Spectrum Analyser TR4172

Thanks, Jeremy. Yeah- can't read it unfortunately. I even tried the enhanced CSI image function... my computer made the required beeps and scanning noises, but no increase in detail was found. I don't know why it always works on TV but never on my equipment

I will try the plotter function when I get it back together.

Regards-
-Matt
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Old 11th Mar 2021, 9:28 pm   #112
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Default Re: Spectrum Analyser TR4172

I have two paper instruction manuals Vol-1 and -2. There are no schematics in these manuals. A while ago I found a PDF with VOL-1 and 2 including schematics but the IF1 schematic is missing. If you google KO4BB TR4172 you will find the pdf but I assume that you already have it.

I have mounted the IF1 module back in the analyser but unfortunately Im still missing 12.5 dB? Jeremy what do measure if you do the following:

- Master reset
- Cal -20 dBm 50 MHz at input 1 (level checked with power meter)
- CENT 50 MHz and SPAN 10 MHz
- ATT 0 dB
- ZERO SPAN (Shift, Arrow Up)

At the CRT I see -32.5 dBm. At the IF output at the back I measure -38.6 dBm at 3.33 MHz, see picture. It is wiggling a bit. The calibration screw at the front is at max.

Jeremy, nice that you can make plots via the GPIB interface by accessing the memory. This is also on my wish list. Maybe you can tell me more at a later moment if I have solved the old gain loss issue .

Best regards, Lex
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Old 11th Mar 2021, 9:58 pm   #113
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Default Re: Spectrum Analyser TR4172

My TR4172 hasn't been used for quite a while but I'll try and lug it out over the weekend and see if it still works OK. Hopefully it will still work. I suspect the cal data backup battery will need a decent charge first. The last time it was used it only just got through the automated self cal routine.

Note that if the analyser has a problem and it still somehow gets through the automated cal routine it can cause some very strange effects with the calibration. All of the settings in the step attenuator have to be accurate and functional and it needs to be able to step cleanly between the RF input connectors. Before running the cal routine I used to click these steps and switches back and forth several times to make sure the contacts weren't a bit oxidised. I think the auto cal routine has total faith in the accuracy of the 10dB step attenuator and if there is a momentary poor connection during the routine it paints the error into the calibration tables. This can cause errors in the accuracy of the log amp as the calibration results will be used to wrongly correct the (innocent?) logamp.

My other TR4172 was mainly bought for spares. I did get it working before storing it but it wasn't quite as good as the first one in terms of noise floor.
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Old 11th Mar 2021, 10:30 pm   #114
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Default Re: Spectrum Analyser TR4172

I have what likely everyone else has found; four documents:
-TR14501A/B and TR4172/4173 Connection Manuals, a 34 page .pdf
-A 294 page, nine section .pdf labeled, "Advantest-7993" which is a very thorough user's manual, covering what seems to be all aspects of operation, including GPIB commands.
Unfortunately this original manual had some fold-out pages which weren't folded out.
-TR4172 Spectrum Analyzer Instruction Manual, Vol-1. This is the huge 1092 page, thirteen section (plus appendix) .pdf. Schematics, Mechanical overviews, block diagrams, troubleshooting flowcharts, and the works... except for the interface unit of course. This is the one that I printed out and indexed by section. Double-sided 8.5"x11", it is in a binder about 3 inches thick. I think I heard a forest scream while this one printed.
-TR4172 Spectrum Analyzer Instruction Manual, Vol-2. This is a 186 page document containing all of the part numbers with Advantest and manufacturer's part numbers with descriptions. I also printed this out and indexed it in the back of my binder.

I think the 294 page manual is a repeat of the first 294 pages of the huge manual, but I haven't compared them side-by-side.
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Matt
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Old 12th Mar 2021, 12:07 pm   #115
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Default Re: Spectrum Analyser TR4172

Quote:
Originally Posted by Radio Wrangler View Post
Quote:
Originally Posted by G0HZU_JMR View Post
The handbook does explain some of the more obscure hidden features such as the ability to measure and display electric field intensity in dBuV/m with a suitable dipole antenna.
That could be a useful function very shortly if you've seen the latest OFCOM message to radio amateurs? The thread on it is closed at the moment, waiting for the RSGB to publish their calculator spreadsheet and worked examples.

David
David and Matt,

I've uploaded a clearer image of the pages from the TR4172 Operator's guide here:

https://www.qsl.net/g/g0hzu//RF%20Tr...TR4172_EFI.jpg

I think the equations can be used with any analyser that can display dBuV with a simple maths correction to give dBuV/m using the equations given in the guide. I've never used this feature on my TR4172 but it probably suits tests at VHF and upwards.
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Old 12th Mar 2021, 2:27 pm   #116
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Quote:
have mounted the IF1 module back in the analyser but unfortunately I’m still missing 12.5 dB? Jeremy what do measure if you do the following:

- Master reset
- Cal -20 dBm 50 MHz at input 1 (level checked with power meter)
- CENT 50 MHz and SPAN 10 MHz
- ATT 0 dB
- ZERO SPAN (Shift, Arrow Up)

At the CRT I see -32.5 dBm. At the IF output at the back I measure -38.6 dBm at 3.33 MHz, see picture. It is wiggling a bit. The calibration screw at the front is at max.
I cleared some space in the spare room and set up both the TR4172 and my old HP8566B analyser. They have been running about an hour now and both are working fine. The TR4172 still has its previous cal corrections stored and it is running with the cal screw at its usual part setting. From memory this is probably at 3/4 full. It's not a good idea to try and do a system cal if this is turned to an extreme setting. I think it causes problems with the 95dB logamp and this manifests itself as an incorrect log response near the top of the screen after the calibration is complete. However, this is all remembered from a long time ago.

With your settings it shows -20.1dBm at 50MHz on screen with 0dB attenuator setting. If I set the attenuator to the usual/default 10dB I see -20.0dBm on screen.

With 0dB attenuation I see -24.5dBm at the IF out at about 3.34MHz.

If then connect it all up again and look at the noise floor at 50MHz on a 500kHz span with the ref level set at -40dBm I see a -146dBm/Hz noise floor with the 1Hz noise marker enabled and 0dB attenuation. I think it used to be -147dBm/Hz typical at VHF so maybe I need to leave it running a bit longer and do a recal. It hasn't run the automated cal for a couple of years at least.
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Old 12th Mar 2021, 3:06 pm   #117
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Default Re: Spectrum Analyser TR4172

Jeremy,
I did actually find that info on E field measurements in the "big" manual, section 4, page 60. It is the same procedure but written slightly differently due to the different format of the manual. Your guidebook is much nicer
Lex, IIRC the cal output adjustment is maxed on mine as well, and I think I still can't get quite -20dBm from it. This is yet another thing I need to work on once it's running. Looking at figure 10-8 on page 10-9 I see a few amplifiers used in the calibration generator circuit. Also, the RF chain gain/loss diagram on page 10-14 should be useful.
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Old 14th Mar 2021, 3:09 pm   #118
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Default Re: Spectrum Analyser TR4172

If it helps I've not had any issues with the 50MHz -20dBm calibrator output. Over the years it has been remarkably consistent in terms of accuracy. It uses an ALC loop to keep the level constant and this uses a diode detector and this looks to be temperature compensated. As long as the loop stays in closed loop (constantly correcting itself) then the -20dBm power level should be very consistent because there is only a passive attenuator between the ALC detector and the front panel output. My first TR4172 always gave -19.97dBm or -19.98dBm here year after year when checked with a power meter whilst the TR-4172 still belonged to the company. It really was quite remarkable.

I think the front panel cal control tweaker control adjusts the gain of the receive path.
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Old 15th Mar 2021, 4:58 pm   #119
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Default Re: Spectrum Analyser TR4172

Yes - you're right; I found out this weekend that I can get -20dBm on the test output with no issues; it was the front panel gain control of course... which is where I found the initial issue of the spec an having some deafness when I first got it several years ago.
I got time to work on this over the weekend and ended up going with plan B. I was able to get the IF amp working, but still lacked about 8 dB of gain through just the cavity filter/amp/bandpass filter/ - probably due to boogering up the output circuitry of the amp. So I popped it out of the interface, along with the input coupler/filter, and ran coax from the input to the input of the output bandpass filter in the interface. My path was the 2.05GHz from the mixer, a 3-port circulator, then my cavity filter, then my amplifier I found, then an appropriate amount of attenuation, then the IF interface BPF, then a wide 1.8 to 2.6 GHz BPF I had in my junkbox. Attenuation was chosen to maintain 0dB +/- 1dB. This worked, but the analyzer is still deaf by around 9dB.
Using the cavity filter I have gives me only a fraction of a dB loss, and attenuates out of band signals quite well. I experimented with using just the cavity filter and found that the spec an was happy in this mode as well, without spurs throughout it's range, but of course the 9dB or so of deafness persists.
Next I played with removing the IF interface BPF from the chain and using just the cavity filter, the amplifier, 1.8-2.6GHz filter, and appropriate attenuation to give me about 9dB more of the 2.05GHz signal to the 2nd mixer. This allowed me to obtain the needed total gain to make the input to the spec an where it should be. Of course, this probably gives me about 9dB or so less headroom in total.
I really need to follow the chain to find out where the loss actually is, and put the 2.05GHz chain back to unity gain, probably with just the cavity filter and no amp to make the noise level even quieter.
Unfortunately, something happened to where none of the front panel keys work. Yay - just what I needed with it... another problem. Following the test flowchart, it appears the keyboard interface chip (a D8279C). I couldn't find one in my junkbox, so I'm waiting on one from that auction site.
This guy is fighting me tooth and nail, but I'm determined to win.
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Old 15th Mar 2021, 8:54 pm   #120
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Default Re: Spectrum Analyser TR4172

Matt, what I have noticed is that for certain settings mine sometimes freezes and then I have to give a master reset. I think that this has to do with incorrect power levels (calibration). Jeremey also mentioned that strange behaviour can happen if the calibration is incorrect.

This weekend I have measured the conversion loss of the fist down converter and it was about 11 dB ( -20 dBm Cal and 0 dB ATT -> -31 dBm at IF1 2.05 GHz). Next I have terminated the IF1 and started to investigated the RF block for my old gain loss problem. When I connected it all together I noticed that the frontend was deaf. I suspect that the first mixer is broken and I do not know how this could happen. Im pretty precise and have more than 30 years experience in RF/Microwave . I have remeasured the IF1 gain block and checked the LO power again and it was fine, +21 dBm.

For the RF block I have checked voltages of gain stages, switching of R.B.W. BPF (1.5 MHz and <300 kHz), RF level adjustment (cal. screw on the front) and some LO sources if possible. For the RF gain level adjustment I have noticed that according the schematic it should be 5.5 V 3.5 V and I have measure 2.22 6.12 V. May be it is limited on the frontside board but I did not check this.

I was not able to checked the power levels at the RF part because I do not have a RF probe. Unfortunately there are no interfaces where you can measure it unless you cut the circuit. A second thing what I have noticed is that the 1.84 GHz LO power out of the RF block going to the TG is less than the 8 dBm which is mentioned in the schematic. This signal is also going to the 2nd mixer (amplified). I have measured the power at the output of the 1.84 GHz B.P.F. which is a separate block outside the RF block, connected with semi-rigid. I have measured about 0 dBm at the BPF output and the loss of the filter is 4 dB which means that out of the RF block it is about 4 dBm. Matt are you able to measure this for comparison.

Summarised, one step forward and two steps back .
73, Lex
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