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Re: Shielded probe cables?

 

Hi,

This might be what you are looking for:


I don't know pricing and/or if they sell in small quantities.

Regards,

/John





On Sat, Nov 30, 2024, 9:17?AM Mark Litwack via <mlitwack=[email protected]> wrote:
I don't know a manufacturer source, but one way to get nice tiny coax is to cannibalize an HP/Agilent logic analyzer chassis-to-pod "ribbon" cable.? The individual coax runs in the ribbon separate easily from each other, so any grouping down to one coax is possible.? A 40-pin cable will yield 36 x 50" of lossy coax, and the 90-pin version will yield 44 x 45" of (approx) 93 ohm impedance regular coax.
?
Another approach would be to just use the HP/Agilent probing system and make an adapter to connect to your KingstWiz.? You'd probably want to use the 40-pin probing system since the 90-pin system can be much more expensive.? With a 10kohm termination in the adapter, the 40-pin system would present the signal divided by 10, if the KingstWiz can handle that.
?
-mark
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On Sat, Nov 30, 2024 at 03:53 AM, Anders wrote:
If we think about the nice logic cables that come with the HP MSOs, ie a flat, presumable shielded cable, a box and then thin, flexible, presumable shielded cables that go to the probes. I would love to have something similar for my KingstWiz 32 ch analyser. Anyone know a good source for thin, flexible, shielded cables?
Re: Shielded probe cables?

 

I don't know a manufacturer source, but one way to get nice tiny coax is to cannibalize an HP/Agilent logic analyzer chassis-to-pod "ribbon" cable. ?The individual coax runs in the ribbon separate easily from each other, so any grouping down to one coax is possible. ?A 40-pin cable will yield 36 x 50" of lossy coax, and the 90-pin version will yield 44 x 45" of (approx) 93 ohm impedance regular coax.
?
Another approach would be to just use the HP/Agilent probing system and make an adapter to connect to your KingstWiz. ?You'd probably want to use the 40-pin probing system since the 90-pin system can be much more expensive. ?With a 10kohm termination in the adapter, the 40-pin system would present the signal divided by 10, if the KingstWiz can handle that.
?
-mark
?
On Sat, Nov 30, 2024 at 03:53 AM, Anders wrote:

If we think about the nice logic cables that come with the HP MSOs, ie a flat, presumable shielded cable, a box and then thin, flexible, presumable shielded cables that go to the probes. I would love to have something similar for my KingstWiz 32 ch analyser. Anyone know a good source for thin, flexible, shielded cables?
Re: Troubleshooting a 8591e with opt 130

 

¿ªÔÆÌåÓý

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Marco,

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For your control LOG/LIN switch, all seem good.

For third converter RF CAL GAIN, I have 7.454V for -20dBm, but with CORR=OFF, same DC voltage, but -13.6dBm.

For -20dBm on screen, I have -43.5dBm at AUX IF OUT at 21.4MHz, this is the input signal to LOG/LIN amplifier & detector.

And for CORR=OFF, I have -37.6dBm.

?

Since the result between LOG and LIN are different, it is certain that there is a problem, alignment or defective parts.

?

?

Yes, the most logical thing would be to start with the G4-G5 and G6 controls.

Are the potentiometers, OK?

I would measure their ohmic value in the circuit to have a reference.

Maybe these potentiometers are defective, or someone has touched these alignments.

?

Yves
Re: HP 8341B 1992 firmware version

 

Hi?Saevar, Dmitrij,
It turned out that my 8341B sweeper has 1986 firmware and it has only two eproms soldered. Will it be OK to solder four eproms with 1992 firmware?
Best regards, Wojciech
Re: Shielded probe cables?

 

On Sat, Nov 30, 2024 at 12:53 AM, Anders wrote:
KingstWiz 32 ch analyser.
It's probably a Kingst LA5032 32 channel logic analyzer.
Though, their could also be a "KingstWiz 32 ch analyser"
Who knows?
I believe, I have a CheeseWiz 32 cheese analyser" ... somewhere
but, like the OP... perhaps... I don't know what I got.
Re: VNA Resonance Methodology

 

OK thanks. As you can see, you can measure both resonance and Q at the same time with the shunt resonator method. The null frequency gives the resonant frequency and the depth of the notch can be used to predict the Q. However, the port match of the VNA has to be very close to a true 50 ohms resistive for the notch depth measurement. The source match (port 1) has to be especially close to 50 ohms of errors creep in. The old HP 87xx series of VNAs don't have a very good (uncorrected) source match at low frequencies so it's best to fit something like a known good 15dB attenuator at the end of the port 1 cable and a 10dB attenuator at the end of the port 2 cable if you every try and measure Q based on the depth of the notch. Then do a thru cal to normalise to 0dB and then measure the notch depth.
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If you just want to look for resonance then you don't need to calibrate anything, just do an uncorrected s21 measurement and look for the null frequency at resonance.
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If you want to try making a physically bigger solenoid using thicker wire (to achieve a higher Q) I can help predict the Q using the software program if that helps?
Re: Troubleshooting a 8591e with opt 130

 

Yves,
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I double checked and filled the table like you did
? Log Lin
VLOG2 -7.990 10,092
VLOG3 -8,015 10,089
VLOG1 -8,07 10,087
-8VT -8,236 -8,236
VLIN 3,672 -6,624
VLOG/VLIN 3,695 -8,005
Some differences but not directly issues i'd say.
?
I checked but don't have a replacement LM339 on hand. I doubt that's the issue though, since at the output of the LM339 the full swing is measured, it's only after the resistor division in the "Gain Control Lines" part that the voltages are not reaching the expected levels anymore. So it seems the circuit after the Gain control lines division is loading it incorrectly.
?
I also checked the REF Level Cal signal. It's the output of a DAC on the Analog interface board, U106 pin 16.?
Measured in factory default cal and after self cal. level changes so it seems to function, don't know if its correctly though.?
? Fact Def cal Self cal done
REF Level Cal 8,85V 6,864V
Mrkr freq 300MHz 300MHz
Mrkr level -14,1dBm -5,1dBm
?
Since my analyzer measures the cal signal in LIN mode at around -30dB~-35dB when in factory default cal it wouldn't surprise me if the additional gain is added because the signal is measured too low in LIN mode during selfcal.?
? Fact Def cal Self cal done
MKR Freq 292,7MHz 300,05MHz
MKR Level Log -14,3dBm -5,1dBm
MKR Level Lin -27,8dBm -20,2dBm
?
I'm starting to think the full Log amp adjustment might have to be done because the lin and log gaines are perhaps not what they should be.. Although maybe the G4/G5/G6 voltage levels should be fixed first??
?
Marco?
?
Shielded probe cables?

 

If we think about the nice logic cables that come with the HP MSOs, ie a flat, presumable shielded cable, a box and then thin, flexible, presumable shielded cables that go to the probes. I would love to have something similar for my KingstWiz 32 ch analyser. Anyone know a good source for thin, flexible, shielded cables?
Re: Tantalum Capacitors

 

I've watched a few of his videos, and his troubleshooting methods are irritatingly slow. He reminds me of newly graduated tech school students that shotgun ded equipment rather than develop the skills to make repairs affordable. I repaired hundreds of 8-bit computers with a logic probe and a 500 KHz scope before I finally bought a Tek 453A. He seems more interested in showing his gadgets than doing logical troubleshooting. You learn the most common failures, and good methods to find the problem/ Bad AM was a high failure item, which a lot of foreign made ICs in questionable packaging.? A look at th data line on each would quickly reval the worst , and I would replace all sigh if four or more were bad Some brands were so flakey that you recognized them, on sight as needing replaced. I repaired most of it without schematics.

On Fri, Nov 29, 2024 at 8:42?PM Roy Thistle via <roy.thistle=[email protected]> wrote:

On Wed, Nov 27, 2024 at 11:34 PM, DavidK wrote:
Adrian basement
Adrian's Digital Basement
But...AFAIR... he's a software 'engineer' whose hobby (fixing old 8 bit computers), turned into a full time YouTube channel.
Well... okay.
But.
There are much better people on this forum.
Re: Troubleshooting a 8591e with opt 130

 

¿ªÔÆÌåÓý

Marco,

?

For my 8595E, module A12, after power on, if CORR=ON, IFA1-A4 are OFF and IFA5 is ON.

From this point on, only when the REF LEVEL is at 0, +10, +20, +30, +40, +50 and +60dBm, IFA5 is ON, all other cases, IFA5 is OFF.

?

If I put CORR=OFF, the level read from the 300 MHz calibrator is -13dBm.

So, I put an external fixed attenuator of 6dB, for a level of -19dBm, and I did a CAL AMPTD.

I looked if IFA5 becomes ON by testing the different possible REF LEVEL, but this did not change anything in the previous results.

Either the attenuation values ??are predetermined, or, A12 is tested in relative mode from the external calibrator, that would be the reason why this did not change anything.

?

On the other hand, the fact of having reduced the signal from the 300 MHz calibrator, changed the value of the gain at the third converter output: REF LEVEL CAL.

It is a variable gain amplifier controlled by DC voltage. This calibration is done in the first minute of the CAL AMPTD calibration.

Yves
Re: Tantalum Capacitors

 

On Wed, Nov 27, 2024 at 11:34 PM, DavidK wrote:
Adrian basement
Adrian's Digital Basement
But...AFAIR... he's a software 'engineer' whose hobby (fixing old 8 bit computers), turned into a full time YouTube channel.
Well... okay.
But.
There are much better people on this forum.
Re: VNA Resonance Methodology

 

jmr, leaving Q aside for now I'm going to try your shunt arrangement out. It just seems like this should work better than the way I'd been attempting it; much more logical. Many thanks for that idea!
?
J.
Re: Tantalum Capacitors

 

FWIW:
Here in Colorado Springs (dry climate, high altitude) I seem to have MUCH fewer cap failures than everyone else. I can't remember the last time I found a tantalum that was actually bad (and certainly not shorted). I have NEVER seen an exploded Rifa cap.
I *occasionally* find a dried-out electrolytic (especially in ordinary commercial radios and such), and some old paper coupling caps turn out to be a bit leaky in commercial gear (but almost never in higher-standard gear like HP test equipment).
?
I *assume* that the dry air and/or high altitude is the difference.
I have NEVER felt the need to pre-emptively replace caps, like so many folks seem to think is essential. One of my 1960's-vintage HP machines had two examples of dried-out electrolytics of a specific brand/type, so I did replace a couple more of the same type that were in it (even though they were still working).
?
Pete
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Re: Troubleshooting a 8591e with opt 130

 

¿ªÔÆÌåÓý

Marco,

?

This is my measures about LOG/LIN switch

?

?

The LM339 U108 has open collector outputs, as the graph shows, although it is not to scale with the configuration in your 8591E, but you can see that if the sink current exceeds 10mA, the voltage will quickly rise again depending on the current. If you ever had a replacement LM339, it might be a good idea to change it to see how it behaves, or by isolating the outputs one by one, see if the voltage drops back to the nominal value.

?

Yves,
Re: VNA Resonance Methodology

 

Here's what happens if an attempt is made to measure the Q via a reflection method (s11) using a modern lab VNA.
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This is asking a bit much of the VNA as the reflection coefficient is very close to 1 and it is trying to make a vector measurement here. However, it did fairly well I think and it shows a Q of just over 130. The graph below shows the Rs and the Q across 1 to 2 MHz.
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You can see that the green Q curve is very noisy and there will also be additional uncertainties creeping in. The Rs is just under 4.5 ohms but the red Rs trace is also very noisy. This isn't a very trustworthy test method in this case.
?
Re: VNA Resonance Methodology

 

See below for an image of a couple of my old Q measuring jigs. I haven't used these for a long time. The larger one mounted on pillars has a resistively tapped (low impedance) source and it has an active buffer with a capacitive tap at the input. This gives a really high input impedance and I used to use this to measure via the 3dB method. But I discovered that the passive method is usually adequate using E and H field probes. This allows both ends of the series resonator to be grounded and the resonator just gets tickled remotely via the probes.
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The smaller jig was an attempt to make an ultra low Z source up at VHF using a very low Z transmission line. The inductor gets connected very close to the ground end of the transmission line and then to ground. I then used to use an E field probe with it as the receiver.
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The insulator under the copper line is extremely thin. I can't remember how well this worked as I abandoned it in favour of the current methods I use. In theory at least, the source impedance was very low up at VHF.
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?
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Re: VNA Resonance Methodology

 

Hi Ed thanks. In addition to what I described already I do have various Q measuring jigs here including one with a Hi Z amplifier as you describe. It's a bit of a mess but it does work quite well. I also use a capacitive divider at the input to the high Z amplifier to step up the input impedance. The risk with active buffers like this is that they can introduce negative resistance at the input and this can upset the accuracy of the process. So I tend to try and use the passive jigs as much as possible. However, I did try very hard to avoid having any negative resistance with my Hi Z buffer.
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To get low source resistance, I've got various options here. I have a low Z transmission line launcher and also a low resistance divider as used in some Q meters. However, these don't work very well up at VHF and UHF.
That's partly why Q meters don't perform well at higher frequencies. I prefer to use other methods like the shunt resonator method or the E and H field probe method. These have served me well for many years up at VHF and UHF.?
Regards
Jeremy
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Re: VNA Resonance Methodology

 

jmr,
?
you can do the Q more directly with your VNA if you can add a high-Z RF amplifier, and likewise, some Z reduction at the source. The trick with Q-meters is to get ideally zero output Z in the source, and infinite input Z in the voltage amplifier. In the HP4342A these are around 20 milliohms and 100 megohms parallel 2 pF, respectively. These are hard to achieve in just wiring stuff together, so the DUT deck especially is quite a mechanism including the source, amplifier, and tuning capacitor, all built to minimize parasitics.
?
With the VNA you can measure more stuff and figure out how to scale and compensate for everything, while the old Q-meters can't, so they had to rely on precision and performance up front.
?
Ed
Re: VNA Resonance Methodology

 

The next test method I tried is the classic shunt resonator method. This relies on the VNA ports being exactly 50 ohms so I pad the ends of the cables with 15dB and 10dB attenuators to really make sure the source and load is close to 50 ohms. You can see this gave a resonator null at about -16.3dB at 1.48 MHz. The other way to correct the ports to 50 ohms is to do a full two port calibration of course.
?
This method yielded a Q of 128.8 at 1.48 MHz as shown in the excel sheet below. This agrees very well with the 3dB bandwidth method although the 3dB BW method can show a higher Q depending on the impact of the self capacitance of the solenoid. In this case, there isn't much difference because the self resonant frequency of the solenoid is about ten times higher in frequency than the 1.48 MHz test frequency. I think if I revisited the 3dB BW method and used more averaging the 3dB BW derived Q might be just over 130.
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Re: VNA Resonance Methodology

 

Oops - I lisdexified it. It's HP4342A not 4243A.?? Ed
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