Hello All, I have an hp1611A Logic State Analyzer that has two broken 15-pin, 2-row card-edge connector sockets, part number 1251-1886. Would anyone have some of these sockets so I could fix this motherboard? Thanks in advance. Christopher   
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Re: HP 8405A Vector Voltmeter Probes
Thanks, I'm going to consider all diode types from all manufacturers so I'd be happy to use BAT parts if they work OK. I'd welcome any other suggestions as well. I do have an old Avago diode kit here with their whole Schottky diode range in it but this is all in SMD.
I did another test using a decent ESGD sig gen as the source. I used my (SMA) homebrew compensated tee with the far end terminated in a decent 18GHz SMA load. Normally, I would externally level the generator using a power meter and external ALC but in this case, I'm not after great precision (yet). This sig gen is usually well within +/- 0.1dB across this frequency range when using its own internal levelling as long as I pad the output and don't turn the level up too high.
If I test the channel A probe for flatness with my homebrew tee or a homebrew compensated termination I see a gradual upwards slope up to about 500MHz. However, this slope is only about +0.25dB in total. I don't think this is in the sig gen. Some of it will be in my tee and some of it in the probe itself. However, this agrees with my old HP 8405A when I do the same test on its channel A probe.
If I then plug the channel B probe PCB into the channel A probe on the newer HP 8405A, the performance degrades a lot in terms of flatness. It was so disappointing I didn't write down the results but it exceeded 1dB by about 150MHz and hit +2dB by 250MHz.?
So something is clearly wrong with this probe element. I have a fair bit of design experience designing Schottky detectors up to a few GHz and usually when something like this upwards slope happens it will be a function of the input capacitance and any stray package inductance in the overall detector design. This typically causes some peaking up towards UHF. Adding damping resistance can help but this can spoil the input Rp.
I think it could take me a while to find the right diodes to use, but I'm in no hurry as I have the other HP 8405A here and I rarely use it anyway. I want to get this newer HP 8405A working really well, hopefully as good as the older one in terms of probe performance :)
Note that even in its current state I think it would be fine to use up to about 100MHz even with the wrong diodes in the probe. I suspect that the majority of 8405A uses will typically use these meters below 150MHz.
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Re: HP 8405A Vector Voltmeter Probes
I agree that your measurements are trustworthy and so the diodes are indeed the main suspect.
Dave Wise’s suggestion of a BAT62 is a great one if you don’t mind a breakdown voltage that is a bit less than the spec’d allowable input voltage.
And they’re more readily available than the original through-hole parts.
Tom
Sent from an iThing; please forgive the typos and brevity
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On May 6, 2024, at 11:09, jmr via groups.io <jmrhzu@...> wrote:
?I'm using an Agilent E5071B VNA and a decent cal kit and I use the fixture simulator feature in the VNA to correct for the fixture. I normally do this stuff up to many GHz so I think the fixture is fine.
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Re: HP 8405A Vector Voltmeter Probes
I'm using an Agilent E5071B VNA and a decent cal kit and I use the fixture simulator feature in the VNA to correct for the fixture. I normally do this stuff up to many GHz so I think the fixture is fine. The diode repair/fitment looks fine apart from the fact that the diodes are different. I'm also measuring the relative differences between healthy probes (they all agree) and the modified probe (shows higher capacitance and poor Rp). You can see the difference below. Channel B obviously has a problem with input capacitance and the Rp is also degraded up at VHF. Also, if I do a flatness test across 10MHz through to 300MHz, my old HP 8405A meter and probes agree within <0.3dB up to about 300MHz. This meter hasn't been adjusted in about 10 years so this is a good result I think. The newer HP 8405A is obviously poorly because the response isn't as flat and the two probes have up to a 1.5dB difference between them across this frequency range.? So something is obviously wrong with it and I think it will be the repair on probe B. It might be possible to improve things with internal compensation but probe B is obviously not right. The capacitance is too high for one thing. These diodes need to be replaced with something closer to the correct part. I think the official HP 'tee' in the HP 11570A kit will be designed for a probe with 2.5pF input capacitance so it's obviously going to cause some issues if used with a probe that now has 4pF input capacitance. I don't have an 11570A kit here but I do plan to buy one at some point. I have a homebrew versions of the tee here but they are ugly lashups and I rarely use them. They are designed for a probe with 2.5pF capacitance though. 
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Re: HP 8360-Series Sweeper CLIP soon available on KO4BB
Can you upload this to some other site in the meantime? The verification seems to take too much.
Il giorno ven 3 mag 2024 alle ore 18:30 Kurt Poulsen via <kurt= [email protected]> ha scritto: Hi Tom In the folder 07 Recent uploads it is listed as but no to download HP 83620 86340 86350 Synthesized Sweeper Service Manual-HP8360-SeriesComponent-LevelServiceManualVol1&2 Kind regards Kurt ? Am I too stupid to find it or hasn't it been verified yet?
I'm excited to see the CLIPs.
Tom DG8SAQ
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Re: HP 8405A Vector Voltmeter Probes
How about BAT62?
Dave Wise
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What's your measurement setup, and what capacitance (and resistance)
values are you seeing?
If you're seeing significantly higher capacitances, then I wonder about
fixturing. Or maybe whoever did the repair wasn't careful about parasitics.
If you're seeing just somewhat higher C and lower R, then perhaps you
could try some 1N5711s. These are often double-marked as 5711/6263, but
the original 6263 had 10-15% or so higher capacitance, IIRC.
That is a fine instrument, for sure, and I hope you will get it back to
like-new performance. It's also fun to use as a front-end for a 1GHz ETS
sampling scope.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 5/6/2024 9:41 AM, jmr via groups.io wrote:
> The main problem is that the input capacitance of the probe is too
> high and the Rp is lower than it should be up at VHF when compared to
> a good probe. I think this could be caused by the wrong choice of
> diodes (1N6263). I won't know for sure until I'm able to take the
> diodes out of the probes. It's not my VVM yet so I can't do any
> further internal testing.
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Re: HP 8405A Vector Voltmeter Probes
What's your measurement setup, and what capacitance (and resistance) values are you seeing?
If you're seeing significantly higher capacitances, then I wonder about fixturing. Or maybe whoever did the repair wasn't careful about parasitics.
If you're seeing just somewhat higher C and lower R, then perhaps you could try some 1N5711s. These are often double-marked as 5711/6263, but the original 6263 had 10-15% or so higher capacitance, IIRC.
That is a fine instrument, for sure, and I hope you will get it back to like-new performance. It's also fun to use as a front-end for a 1GHz ETS sampling scope.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 5/6/2024 9:41 AM, jmr via groups.io wrote: The main problem is that the input capacitance of the probe is too high and the Rp is lower than it should be up at VHF when compared to a good probe. I think this could be caused by the wrong choice of diodes (1N6263). I won't know for sure until I'm able to take the diodes out of the probes. It's not my VVM yet so I can't do any further internal testing.
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Re: HP 8405A Vector Voltmeter Probes
The main problem is that the input capacitance of the probe is too high and the Rp is lower than it should be up at VHF when compared to a good probe. I think this could be caused by the wrong choice of diodes (1N6263). I won't know for sure until I'm able to take the diodes out of the probes. It's not my VVM yet so I can't do any further internal testing.
This VVM is in such good condition it deserves to be repaired properly and if I do buy it I will service/adjust it to try and get as close to the original performance as possible.
I've got lots of the HP accessories to go with these meters plus I made a few of my own plus I have various directional couplers to use with it.
It's all a bit nostalgic because I also have a couple of modern lab VNAs here, but the HP 8405A is a classic instrument and it's also quite educational to use. I usually use the DMM recorder outputs at the back for voltage and phase, but I might also experiment by coupling up an Analog Discovery 2 to the 20kHz outputs and code it up to measure voltage and phase at 20kHz.?
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I have used these. 0.5mm CS is standard.
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Re: HP 8405A Vector Voltmeter Probes
Those diodes should work fine, as long as they're matched (for both forward voltage and capacitance -- and be sure to tweak the adjustments for balance, as described in the manual). What problems are you seeing with them?
You'll want to replace them in matched quads for best performance. I once repaired a probe that had "never worked right", according to its most recent owner. It had been repaired before by someone who had replaced just one of the diodes. Replacing all four with 1N5711s (pretty much the same as 1N6263) that came from consecutive positions on a tape worked fine. If you can find some HSMS-280x surface-mount parts, they should work very well (these contain 1N6263-equivalent devices). There are even some in that series that are in the bridge configuration (though rare; I've never found them for a reasonable price).
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 5/6/2024 6:24 AM, jmr via groups.io wrote: Hi
I know this question has been asked numerous times on the internet and it has been discussed here before, but does anyone know the part number for the Schottky diodes in the HP 8405A sampling probes?
I'm aware of the Richard Carey W6RLC pdf document that suggest using 1N6263 diodes but looking at the datasheet, I think the 1N6263 is not going to be the same as the original diodes. I really want to restore this VVM to full working order and it has some issues with the probes.
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Re: HP 400H AC VTVM Difficulties
On 5/6/24 11:21, Jim Adney wrote: Thanks for posting that Dave; I was not aware of that info. Is hparcive.com the site that people on this group are running? I tried to find out how you found the 400D-2C Service Note, but had no luck searching for it there. I was hoping to find more info, but there's no link to a "Service Notes" section, and even a general search for 400D came up empty. So how did you find this?
Or did you know it was there because you were the one who put it there?
I'd say that the directory on the home page could use a Service Notes entry. If you're talking about HPWiki, no, hparchive.com is not that. There is a link for Service Notes on the front page of HPWiki, and 400D-2C is there. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Re: HP 400H AC VTVM Difficulties
Hparchive is run by Glenn Robb; I don’t remember him posting here.
Dave Wise
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On May 6, 2024, at 8:58 AM, Dave Wise <d44617665@...> wrote:
? On the front page of hparchive, in the paragraph “HP Archive’s purpose”, the next to last sentence contains a link to service notes. Then just search for 400.
Dave Wise
On May 6, 2024, at 8:21 AM, Jim Adney <jadney@...> wrote:
?On Sun, May 5, 2024 at 07:39 PM, Dave Wise wrote:
You also need Service Note 400D-2C, attached here and hosted at ?.
Thanks for posting that Dave; I was not aware of that info. Is hparcive.com the site that people on this group are running? I tried to find out how you found the 400D-2C Service Note, but had no luck searching for it there. I was hoping to find more info, but
there's no link to a "Service Notes" section, and even a general search for 400D came up empty. So how did you find this?
Or did you know it was there because you were the one who put it there?
I'd say that the directory on the home page could use a Service Notes entry.
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Re: HP 400H AC VTVM Difficulties
On the front page of hparchive, in the paragraph “HP Archive’s purpose”, the next to last sentence contains a link to service notes. Then just search for 400.
Dave Wise
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Show quoted text
On May 6, 2024, at 8:21 AM, Jim Adney <jadney@...> wrote:
?On Sun, May 5, 2024 at 07:39 PM, Dave Wise wrote:
You also need Service Note 400D-2C, attached here and hosted at ?.
Thanks for posting that Dave; I was not aware of that info. Is hparcive.com the site that people on this group are running? I tried to find out how you found the 400D-2C Service Note, but had no luck searching for it there. I was hoping to find more info, but
there's no link to a "Service Notes" section, and even a general search for 400D came up empty. So how did you find this?
Or did you know it was there because you were the one who put it there?
I'd say that the directory on the home page could use a Service Notes entry.
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Re: HP 400H AC VTVM Difficulties
On Sun, May 5, 2024 at 07:39 PM, Dave Wise wrote:
You also need Service Note 400D-2C, attached here and hosted at ?.
Thanks for posting that Dave; I was not aware of that info. Is hparcive.com the site that people on this group are running? I tried to find out how you found the 400D-2C Service Note, but had no luck searching for it there. I was hoping to find more info, but there's no link to a "Service Notes" section, and even a general search for 400D came up empty. So how did you find this? Or did you know it was there because you were the one who put it there? I'd say that the directory on the home page could use a Service Notes entry.
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Re: HP 8405A Vector Voltmeter Probes
The HP part number for the diodes might actually be 1901-0517 rather than 1901-1517. I really don't know how the HP system works. See below for a measurement of the probes from my really old HP 8405A for channel A and B. I didn't bother using a narrow RBW or averaging so the plot is a bit noisy once Rp is above about 40k ohms at lower frequencies.? I think these probes contain the original diodes. You can see that channel A and B both have an input capacitance of just under 2.5pF. The Rp is 100k as expected at low frequencies and this gradually reduces with increasing frequency (as expected). Both probes agree very closely for Cp and Rp vs frequency. Sadly, the 'repaired' channel B probe in the newer HP 8405A VVM shows about 4pF input capacitance and the Rp resistance is a fair bit worse up at VHF and UHF.? 
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Re: HP 8405A Vector Voltmeter Probes
Thanks. I still have a large bag of HP 5082-2800 glass diodes here in a little HP envelope dated 1974. There were originally 250 diodes in it but it's down to about 50 now.?
Once I know the HP 8405A is mine (I've made an offer) I plan to remove a good diode from the good probe and measure it on a curve tracer and also measure it on a VNA.
I've measured the input impedance of the probes across 2-1000MHz and it's easy to spot that the repaired probe has too much capacitance and the Rp is much lower up at VHF and into UHF.
I need to find diodes that give the correct input Cp capacitance and Rp resistance vs frequency when fitted to the probe.
I also need to check out the good P JFET on a curve tracer and measure its s-parameters using a VNA up to 1GHz or so. I've done this many times for N channel JFETs but not P channel.
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Re: HP 8405A Vector Voltmeter Probes
Someone on this site wrote IIRC, when I replaced these years ago, I just matched
pairs of 5082-2800 schottky diodes on a curve tracer, little black glass guys
with gold leads. Clear glass ones worked too! I used regular solder &
tweezers for heat sinks on the diode leads (3 hands). HP 8405 Vector VM &
3406 sampling RF VM, same probe design, basically. Sorry I can't give credit, this was saved in my notes but I should save the author.
Hi
I know this question has been asked numerous times on the internet and it has been discussed here before, but does anyone know the part number for the Schottky diodes in the HP 8405A sampling probes?
The black diodes in the probes of this particular vector voltmeter show three lines of text on the diode body.
HP 1
517
152
I assume this means HP 1517 followed by 152
I suspect the HP part number above will be for a matched set of diodes so this part number is for four diodes perhaps? So if this is the case, I would need to know the part number for a single (unmatched) diode.
Looking online I've found HP 1901-1517 and this cross references to 5082-5414.
I have another much older HP 8405A here and it has diodes with coloured bands.?
Orange White Orange? (393?)
Orange White Red (392?)
All research draws a blank in terms of finding a part number.
I'm aware of the Richard Carey W6RLC pdf document that suggest using 1N6263 diodes but looking at the datasheet, I think the 1N6263 is not going to be the same as the original diodes. I really want to restore this VVM to full working order and it has some issues with the probes. It looks like someone has fitted 1N6263 diodes to probe B to repair it but I want to do a proper job of restoring the performance of the probes. The P JFET has also been replaced as per the Richard Carey W6RLC pdf document. At some point I'll need to see if this JFET is OK to use. However, it's the diodes I'm most concerned about.
This HP 8405A is in excellent unmarked condition otherwise, and it's a late model made in 1986. It's not mine, but if the proper diodes can be found then I will probably buy it to replace my much older HP 8405A.
Thanks!
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HP 8405A Vector Voltmeter Probes
Hi I know this question has been asked numerous times on the internet and it has been discussed here before, but does anyone know the part number for the Schottky diodes in the HP 8405A sampling probes? The black diodes in the probes of this particular vector voltmeter show three lines of text on the diode body.
HP 1
517
152
I assume this means HP 1517 followed by 152 I suspect the HP part number above will be for a matched set of diodes so this part number is for four diodes perhaps? So if this is the case, I would need to know the part number for a single (unmatched) diode. Looking online I've found HP 1901-1517 and this cross references to 5082-5414. I have another much older HP 8405A here and it has diodes with coloured bands.? Orange White Orange? (393?) Orange White Red (392?) All research draws a blank in terms of finding a part number. I'm aware of the Richard Carey W6RLC pdf document that suggest using 1N6263 diodes but looking at the datasheet, I think the 1N6263 is not going to be the same as the original diodes. I really want to restore this VVM to full working order and it has some issues with the probes. It looks like someone has fitted 1N6263 diodes to probe B to repair it but I want to do a proper job of restoring the performance of the probes. The P JFET has also been replaced as per the Richard Carey W6RLC pdf document. At some point I'll need to see if this JFET is OK to use. However, it's the diodes I'm most concerned about. This HP 8405A is in excellent unmarked condition otherwise, and it's a late model made in 1986. It's not mine, but if the proper diodes can be found then I will probably buy it to replace my much older HP 8405A. Thanks!
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Hello to All,
We are trying to repair an Agt N5230A-220 of one of our customers but we cannot find the fault.
The VNA starts, displays the boot options, but does not boot to the OS, it shuts down then restarts (see video 1).
We tested the CPU and it works (see video 2). Is this an Agilent OS problem?
If anyone can help us I would appreciate it.
Video 1: https://photos.app.goo.gl/iauBvVwxhFiXgSqX6
Video 2:
Thanks in advance.
BR.
Antoine
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Re: Another 3GHz 53132-68003 Chanel 3 option design for the 53131A and 53132A
Yves:
So the 12GHz board likely has a divide by 512 so the hardware sees the same frequency range as the 3GHz board and the X4 scales it up to the correct frequency for display.
At 18MHz the 12GHz board output would output a bit over 35MHz.
Thanks for posting the text file with the necessary changes.
ed
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Christopher Tucker
Sam Reaves
Dave McGuire
Electro4lease