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Re: HP34702A Ohms converter issues
Joel, your thoughts are always illuminating!
1K range, loaded by my Fluke 8600A in mA mode - 2.08 mA R55+R56 = 2.1V U3-3 to U2-6 = 2.06V Completely consistent, though the wrong values. ;-)? I checked the zeners last night; all are pretty close to their rated voltage except for CR14 which I think is part of the protection circuit and shouldn't be breaking down in normal operation.? I actually tested Q13-14 out of circuit and they seem OK, so something appears to be turning that Darlington pair on too hard.? Replacing Q11 improved the situation on the lower ranges a little, but it's clearly not the major fault.? The voltages on Q12 look OK, though B-E is a little low (probably because the protection circuit isn't being activated?).? I tested it out of circuit and it looks fine.? Not sure where to go next... |
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Re: VNA advice wanted
Dr. David Kirkby from Kirkby Microwave Ltd
On Mon, 11 Feb 2019 at 16:28, Reginald Beardsley via Groups.Io <pulaskite=[email protected]> wrote: Thanks!? That's where it is.? I *really* do need to read the manual.? I just hate reading long texts on a computer. In case you are not aware, VNAs are good around 50 ohms, but the uncertainy in reflection rises quite a bit if the reflection coefficient is high, or obviously in transmission if the attenuation is very high. But an 8753 will have sufficient dynamic range (needed for transmission) for most needs - FAR more than the cheaper USB units. Also be aware there are different defintions for dynamic range for VNAs. The ability to high attenuations may be limited by either * Lack of source power * Receiver overload. In the VNWA you have, the source power is -17 dBm and the receiver overload point is -17 dBm, so they match. But that is not necessarily the case with other VNAs. Having direct access to the receivers, which you can get on an 8753 with an external test set, will gain you about 14 dB in dynamic range, at a loss of accuracy, by going directly into the receiver, without the bridge. There are other techniques more suited to the measurement of high or low impedances, but none have the frequency range of VNAs. But in my opinion at least, an 8753 is hard to beat for a reasonably priced VNA. Personally I would get one with an external test set, but others have advised you to get one with an internal test set. Both options have their advantages and disadvangates. Dave Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, Essex, CM3 6DT, United Kingdom. Registered in England and Wales as company number 08914892 Tel 01621-680100 / +44 1621-680100 |
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Re: VNA advice wanted
开云体育Hi Regi. Measuring the performance of "EMI" filters can be done many ways depending on what kind of data or information is required. There are so many different kinds of filters and so many different applications for them that it is difficult to find just one of two sources of information that will answer all of your questions. Many different filter companies measure things in different ways and few are eager to release their test methodology. I will be happy to help you the best I can off line. Being an old tempest engineer goat my field and EMC has some overlap in different places. As a point of interest have a look at these
papers & sites, if anything it will help introduce you to
many of the terms used and at least provides a primer to the
subject. I will see if I can forward to you additional reading
material in the near future.....has several Dr. appts today and
this week. 73 Gedas, W8BYA Gallery at Light travels faster than sound.... This is why some people appear bright until you hear them speak. On 2/11/2019 1:33 AM, Reginald
Beardsley via Groups.Io wrote:
I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. I presume I'd need to first measure the input and output impedances and then construct matching baluns.. Whatever is not reflected is transmitted except for any absorption due to resistive losses. So except in certain pathological cases reflection does not matter. But sometimes it does. In reflection seismology the water layer reverberation is a major aggravation. I'm afraid I've gone off the deep end. My power feed for my bench is all shielded with Liquatite SL-516 flex conduit. I cut off the cords, and ran them from Appleton 4SS boxes (which I do *not* recommend as it gets *very* cramped). I bought them because they fit the external space nicely, but got beat up pretty badly getting the wires to fit inside. I still need to mount a 20 A EMI filter where I connect to the mains. I've got a filter, but it's rather large and I still need to find a suitable enclosure. This might seem like overkill, but if you investigate the radiated EMI from a GW Instek GDS-2000E series scope you'll be appalled by the radiated EMI. There is *no* shielding on the SMPS. I plan to correct that as I have a bending brake and can fabricate an enclosure, But after discovering the issue decided that shielding my power feed was worth while. Besides which I really did not have room for runnning all the power cords into power strips. The last attempt at that led to a wad of cables of absurd dimension. As for probes, so far Bob Pease has kept me to the strait and narrow. |
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Re: Test fixture for dielectric measurements
On Mon, Feb 11, 2019 at 1:49 PM Dr. David Kirkby from Kirkby Microwave Ltd <drkirkby@...> wrote:
I can maybe do this a bit later when I get the time for it... ?
The test jig has SMA connectors, the BNC's are just adapters.? All the SMA connectors are screw directly onto the test fixture that is all metal. This will probably get more clear when I get some pictures for you.
Askild? |
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Re: 8753A VNA Repair
I have a?TL866 eprom programmer, and they don't cost much on ebay.. It has worked fine for me. I too have a 8562A, and when updating the firmware to latest, I also replaced the eeprom with a 28C16, due to recommendation i did read somewhere.? But i did not follow the procedure in the service manual, I just copied it with my eprom programmer. ?Br, Askild On Mon, Feb 11, 2019 at 11:18 AM Harke Smits via Groups.Io <yrrah53=[email protected]> wrote:
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Re: VNA advice wanted
oops, I meant DSO1102G oscilloscope
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by the way, when you put the 8560A in DC coupled mode, be very careful of not applying any DC voltage to the input specially if the attenuation is low. It can easily kill the mixer On Mon, Feb 11, 2019 at 01:33 AM, Reginald Beardsley wrote: I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. |
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Re: VNA advice wanted
on my 8560E the AC/DC coupling is under Amplitude softkey menu on the second page. It's probably the same on 8560A
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because on my 8596E it is also under the amplitude menu your analogy with seismology is not quite relevant when we talk about a circuit at 30KHz or few 10's or 100's of KHz The size of the whole circuit and all connections is not even 0.001 of the wavelength contrary to the sizes or distances you are dealing with in seismology For evaluating these kinds of low frequency (lumped) circuits I would get an Agilent oscilloscope with built in function generator which has a bode plot software in it like a DSO1104G which is relatively cheap. You can automatically find the bode plot of? V_out / V_in. I'd think with a little bit of imagination one could also set it up to plot the input impedance as well. Or you can get something like an HP 4192A gain and phase and impedance analyzer and measure the transfer function and input/output impedances down to 5Hz same thing can be done with HP 8508A vector voltmeter. On Mon, Feb 11, 2019 at 01:33 AM, Reginald Beardsley wrote:
I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. |
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Re: Test fixture for dielectric measurements
Dr. David Kirkby from Kirkby Microwave Ltd
On Sat, 9 Feb 2019, 16:02 Askild <megafluffy@... wrote:
Is there any chance you could take some detailed photographs and detailed dimensions? I have looked at the manual, but some more details would be nice.? What of the BNCs connect to the guard ring? Whilst I take your point one is making comparisons to air. There is some software from Keysight that supports that fixture, which might be tailored to it.? I believe the electrodes are plated in platinum. I don't know if that's the best possible material to reduce the barrier layer problem. I know getting things gold plated is easy, but I am unsure about platinum.
Yes, I can understand that!
I managed to pick up one of those. I have often wondered if it could be used for liquids too, if one made a small tank to fit inside - like a small fish tank! Although it would make the maths tricky, if the properties of the tanks material were first measured, an analytical solution (excuse the pun) could be derived.? As I write before I have reasonable results with using an air spaced capacitor, but the lack of a guard ring is going to reduce accuracy.?
I have a 4284A & 4285A, which were top of the line instruments in their day. Unfortunately the fixtures sell on the used market for more than the instruments do!
Dave |
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Re: VNA advice wanted
开云体育For occasional use, I like the 8753 for its all-in-one-box construction and simple calibration procedure. I find the 8510 more demanding of the operator, excellent though its performance is.The 8753 was made in very large numbers, so the second hand price is relatively cheap. Experience of them at work has been that they have a good reliability record- we’re still using some that are nearly 30 years old and have needed nothing more than routine calibration. Hope this helps. Regards, Alwyn _____________________________________________________ Alwyn Seeds, Director SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. Tel.: +44 (0) 20 7376 4110 SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________
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Re: HP34702A Ohms converter issues
Hi Greg,
Trying to find some logic process here... Here's my attempt: - Let's first forget about the high-megohm problem, and focus on intermediate ranges for the time being. - On the 1K ohms range, the current through the unknown resistor should be exactly 1mA. In other words, connect a milliammeter as the unknown resistance, the milliammeter should read exactly 1mA. Does this check ? - This means that the voltage drop across the reference resistor (combined R55+R56) should be 1V. Check ? - This 1V drop is equal to the voltage difference between U3 pin 3 (minus 6.2V) and U2 pin 6 (minus 7.2V). Does this check ? Then we'll take it on from there. I hope this helps ! Joel Setton |
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Re: 8753A VNA Repair
Hello Walter and Askild, and others interested.... A very important topic indeed. I was always wondering how long an EPROM would last, in practice. I have a lot of HP EPROM containing equipment that could fail for that reason any time now. I do not have a programmer myself and I would appreciate someone setting up a service for that at a reasonable fee. Maybe its already existing..... The world of eproms seems a bit tricky and I am not an expert here. Besides the 2716's and family are getting more and more difficult to obtain now? In the same line: recently I repaired an HP8562A spectrum analyser that showed Yig tuned filter failures and flatness problems. I tested the RF section thoroughly, finally deciding to re-adjust flatness. Then I quickly saw that all flatness parameters were set at 128, so mid range. Then I understood the EEROM was the culprit. I ordered a 28C16 from a reputable source (not far east) and re-calibrated my precious sa. Problem solved. You bet I immediately ordered a second 28C16 for my spare sa. Btw: you have to replace the EEROM while the sa is turned on! Thanks for raising the topic. Best 73 de Harke
On Monday, February 11, 2019, 7:52:17 AM GMT+1, Askild <megafluffy@...> wrote:
Good tip. And this is a good time to encourage people to upload the firmware they have in their instruments if its not already available, or if you have a newer version than whats available. Not fun to have a perfectly good old test equipment disable due to a rotten eprom. I recently uploaded the firmware from, my?HP 54645A scope, as I could not find it anywhere. My fw version is A.01.01, and latest listed at keysight is 2.0 and asking here gave no reply. I think I still have a couple of firmware's I need to read out and upload, as I have not seen them online, will do next time the instruments is opened up. Br, Askild ?? On Mon, Feb 11, 2019 at 2:14 AM walter shawlee <walter2@...> wrote: This may come in handy for others, I had an 8753A I got off ebay fo rmy RF bench.? It worked for one day, then went into random display and status mode, totally unusable. Most times, I got no display, but sometimes random lines and random LEDs on, no key press response. Rats... |
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Re: Unleveled E4436B
Hi Tim,
You can use:
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Re: HP34702A Ohms converter issues
Oh, there's no doubt that the current source is generating the wrong output.? Measuring the voltage across the test resistor gives a value which matches the erroneous display reading.? What we're trying to figure out is why the current source isn't working properly.? As mentioned, I've replaced all the active components in the ohms converter and am in the process of checking all the passives.? So far, nothing raises a red flag and yet the voltages are wrong.
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Re: 8753A VNA Repair
Good tip. And this is a good time to encourage people to upload the firmware they have in their instruments if its not already available, or if you have a newer version than whats available. Not fun to have a perfectly good old test equipment disable due to a rotten eprom. I recently uploaded the firmware from, my?HP 54645A scope, as I could not find it anywhere. My fw version is A.01.01, and latest listed at keysight is 2.0 and asking here gave no reply. I think I still have a couple of firmware's I need to read out and upload, as I have not seen them online, will do next time the instruments is opened up. Br, Askild ?? On Mon, Feb 11, 2019 at 2:14 AM walter shawlee <walter2@...> wrote: This may come in handy for others, I had an 8753A I got off ebay fo rmy RF bench.? It worked for one day, then went into random display and status mode, totally unusable. Most times, I got no display, but sometimes random lines and random LEDs on, no key press response. Rats... |
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Re: Test fixture for dielectric measurements
In the late 1980s I worked at E. I. DuPont Co at their Engineering Physics Lab in Delaware. We did a lot of dielectric measurements for the company, and also had an 8510 plus the 1970s 8409 automatic network analyzer, a two rack wide series of instruments controlled with a 9836 computer. The basis was the 8410 network analyzer.
One of the typical measurements we made was liquid dielectric measurements. We had a brass cell, with O rings, that looked like a vertical coaxial cylinder. It was filled a certain height with the liquid, and it fitted on top of the HP 4342A Q meter. We made empty and full measurements and plugged the dial setttings into a program that computers K' and K"". I think we had a heat tape around it, and could measure vs temperatur. Later I automated it with a swept measurement system and had the dielectric properties vs temperature.? Keysight and an aftermarket Swiss? company make a surface probe that can measure flat materials and liquids. Damaskos in Pennsylvania also makes some devices. |
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Re: Test fixture for dielectric measurements
In the late 1980s I worked at E. I. DuPont Co at their Engineering Physics Lab in Delaware. We did a lot of dielectric measurements for the company, and also had an 8510 plus the 1970s 8409 automatic network analyzer, a two rack wide series of instruments controlled with a 9836 computer. The basis was the 8410 network analyzer.
One of the typical measurements we made was liquid dielectric measurements. We had a brass cell, with O rings, that looked like a vertical coaxial cylinder. It was filled a certain height with the liquid, and it fitted on top of the HP 4342A Q meter. We made empty and full measurements and plugged the dial setttings into a program that computers K' and K"". I think we had a heat tape around it, and could measure vs temperatur. Later I automated it with a swept measurement system and had the dielectric properties vs temperature.? Keysight and an aftermarket Swiss? company make a surface probe that can measure flat materials and liquids. Damaskos in Pennsylvania also makes some devices. |
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Re: VNA advice wanted
I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A.
I presume I'd need to first measure the input and output impedances and then construct matching baluns.. Whatever is not reflected is transmitted except for any absorption due to resistive losses. So except in certain pathological cases reflection does not matter. But sometimes it does. In reflection seismology the water layer reverberation is a major aggravation. I'm afraid I've gone off the deep end. My power feed for my bench is all shielded with Liquatite SL-516 flex conduit. I cut off the cords, and ran them from Appleton 4SS boxes (which I do *not* recommend as it gets *very* cramped). I bought them because they fit the external space nicely, but got beat up pretty badly getting the wires to fit inside. I still need to mount a 20 A EMI filter where I connect to the mains. I've got a filter, but it's rather large and I still need to find a suitable enclosure. This might seem like overkill, but if you investigate the radiated EMI from a GW Instek GDS-2000E series scope you'll be appalled by the radiated EMI. There is *no* shielding on the SMPS. I plan to correct that as I have a bending brake and can fabricate an enclosure, But after discovering the issue decided that shielding my power feed was worth while. Besides which I really did not have room for runnning all the power cords into power strips. The last attempt at that led to a wad of cables of absurd dimension. As for probes, so far Bob Pease has kept me to the strait and narrow. |
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Re: Hp 8903b display issue u
开云体育The part is branded with the HP part number at the top. A9U18, P/N 1820-2100 is listed as being a Fairchild 3861EPC in the service manual. The 8650 on the third line is definitely a date code.?By 1986, when the particular device in your 8903B was manufactured, Fairchild may have been out of the F8 business. Mostek was a second source for F8 family parts, having released the 3870 in 1977.? If you don’t need the HPIB capability, I think you can remove A9 without any problems.? On Feb 10, 2019, at 20:46, oliver johnson via Groups.Io <nojjamaica@...> wrote:
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Re: HP34702A Ohms converter issues
开云体育Maybe a dumb question have you checked that the current being to applied to the test resistor is actually what it should be? ?A whacked out current source could drive bogus readingsRegards, ? Stephen Hanselman Datagate Systems, LLC (775) 882-5117?office (775) 720-6020?mobile a Service Disabled, Veteran Owned Small Business DISCLAIMER: This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.On Feb 10, 2019, at 19:06, gregdunn@... wrote:
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