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Re: 3586A encoder question
Steve Reeves
If the RPG works better in one direction it may need a small adjustment of the very small set screws on the side of the RPG near the lamp wires. This can serve to balance or direct the light flow.
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Steve Sent from my iPod On Dec 23, 2012, at 6:18 PM, "i8iov" <i8iov@...> wrote:
The RPG (rotating pulse generator, i.e. the encoder) of one of my 3586A's doesn't work well. Clockwise it works well, counterclockwise it is erratic. May it be an issue in the encoder itself? I don't know how these encoders are made (are they optical?). May they fail this way? Before removing the front panel for troubleshooting, I wanted to ask the group for any advices. I could find one on ebay right now, but it would cost 50 USD + shipping. |
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Re: 3586A encoder question
Excellent point. I agree.
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Joe -----Original Message-----
From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...] On Behalf Of Gary Sent: Sunday, December 23, 2012 6:21 PM To: hp_agilent_equipment@... Subject: [hp_agilent_equipment] Re: 3586A encoder question If your RPG is the same as my 8660B the output is 2 square wave chains which lead and lag depending on the direction of travel. You can put your dual trace scope on the outputs and watch the wave forms as you turn the knob and see how the traces look. If they look OK then you might have some decoding chips not working properly. Gary --- In hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com> , "i8iov" <i8iov@...> wrote: doesn't work well. Clockwise it works well, counterclockwise it is erratic. May it be an issue in the encoder itself? I don't know how these encoders are made (are they optical?). May they fail this way? Before removing the front panel for troubleshooting, I wanted to ask the group for any advices. I could find one on ebay right now, but it would cost 50 USD + shipping. Thanks, |
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Re: 3586A encoder question
If your RPG is the same as my 8660B the output is 2 square wave chains which lead and lag depending on the direction of travel. You can put your dual trace scope on the outputs and watch the wave forms as you turn the knob and see how the traces look. If they look OK then you might have some decoding chips not working properly.
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Gary --- In hp_agilent_equipment@..., "i8iov" <i8iov@...> wrote:
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Re: 3586A encoder question
Just sent it direct.
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Let me know if you do not receive it. Joe -----Original Message-----
From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...] On Behalf Of i8iov Sent: Sunday, December 23, 2012 5:57 PM To: hp_agilent_equipment@... Subject: [hp_agilent_equipment] Re: 3586A encoder question Joe, well, as I have some other HP stuff with RPG's, having such an unit as a spare would be a good thing. I already tried reseating the connector with tiny pliers without removing the panel, but had no success. I can't easily follow the troubleshooting procedure suggested in the manual because I lack the required extender board, and I have to proceed empirically. The idea of smooked bulb is reasonable. Yes, I would be pleased to have a look at the schematic, thanks. Antonio I8IOV --- In hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com> , "J. L. Trantham" <jltran@...> wrote: than adequate for the signals to be properly generated.<mailto:hp_agilent_equipment%40yahoogroups.com> [mailto:hp_agilent_equipment@...<mailto:hp_agilent_equipment%40yahoogroups.com> ] On Behalf Of i8iov Sent: Sunday, December 23, 2012 5:19 PM<mailto:hp_agilent_equipment%40yahoogroups.com> Subject: [hp_agilent_equipment] 3586A encoder questionerratic. May it be an issue in the encoder itself? I don't know how these encodersadvices. I could find one on ebay right now, but it would cost 50 USD + shipping. |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 23 December 2012 22:09, pianovt <pianovt@...> wrote:
On the 8752/8753/8720 etc., and pretty much all newer VNAs, even what you call "uncalibrated" is actually calibrated at the factory or at the service center when you send the analyzer for calibration.Is that the same data you are supposed to back up to a floppy? The reason I ask, is that the manuals seem to imply this will make restoring the data much quicker if you have it on a floppy in the event of a failure. But you are suggesting it would be changed when the unit went for cal, suggesting to me there's not much point having it on a floppy. Or perhaps I'm wrong. The problem is that you don't know what cables were used for the factory calibration. Hence, two analyzers that were calibrated with different cables will show different results giving the impression that the hardware is vastly different.In the case of the 8720D, there is a set of cables available (Agilent t 85131F) for this, with the NMD connectors, to ensure a rugged connection to the VNA. I assume it would be calibrated with them. I know the length of them is nominaly 24.5", but at 20 GHz, with a wavelength of 15 mm, slightly differnt cables would give quite different phases. I think, the 8510 was the last VNA which showed true uncorrected hardware performance when the instrument wasn't calibrated. And it was impressive!I assume several of the internal cables were selected to give it this performance. Did the 8510 have a computer inside to do automatic error correction, or was it a manual process? I've used a few VNAs, but never and 8510. I own an 8720D and 8753A. This factory calibration is in a way similar to the user calibration, but the correction constants are saved in non volatile memory and protected with a jumper on the processor board. This then is the default state of the VNA when it powers up without a user calibration.At least on my 8720D, I'm sure it is nowwhere near 55 dB as one of the VNAs reported in this thread. I'm not sure it is even 35 dB. But I always do a user cal. I'm sitting in bed at this minute with the laptop - it has just gone midlight local time. Hence I can't be bothered to go downstairs and switch the VNA on to see what it shows. VladanDave |
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Re: HP-608A Repair
On 12/23/2012 12:34 AM, Max Robinson wrote:
I sent a message earlier regarding the resistors, but I didn't see it appear here. If this is a repeat, I apologize. the gist of the message: The description and part number of the resistors is as follows: 53.3 ohms ¡À1% 1/8 Watt carbon film. HP p/n 0721-0006. They list the mfr as 19701, but I can't find a code-to-name list anywhere in that manual to say who the manufacturer actually is. I'd guess that if you find a source of 1/8 W 1% carbon film resistors made by anybody, they would work. Best regards--doug, WA2SAY [Non-text portions of this message have been removed] |
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Re: 3586A encoder question
Joe,
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well, as I have some other HP stuff with RPG's, having such an unit as a spare would be a good thing. I already tried reseating the connector with tiny pliers without removing the panel, but had no success. I can't easily follow the troubleshooting procedure suggested in the manual because I lack the required extender board, and I have to proceed empirically. The idea of smooked bulb is reasonable. Yes, I would be pleased to have a look at the schematic, thanks. Antonio I8IOV --- In hp_agilent_equipment@..., "J. L. Trantham" <jltran@...> wrote:
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Re: 3586A encoder question
The RPG's for the HP equipment I am familiar with use a T-1, 5 V, 60 mA,
bulb with wire leads. The most common failure is for the bulb to burn out. For an 'intermittent failure', I would wonder about a loose connection at the connector that they may have plugging into the front panel PCB or an internal issue with the RPG itself. I disassembled the RPG on an 8350B and 'reverse engineered' the schematic. Not much to go wrong but I can send it to you if you would like. Perhaps the bulb has developed some 'smoke' and it makes the light less than adequate for the signals to be properly generated. Hope that helps. Good luck. Joe From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...] On Behalf Of i8iov Sent: Sunday, December 23, 2012 5:19 PM To: hp_agilent_equipment@... Subject: [hp_agilent_equipment] 3586A encoder question The RPG (rotating pulse generator, i.e. the encoder) of one of my 3586A's doesn't work well. Clockwise it works well, counterclockwise it is erratic. May it be an issue in the encoder itself? I don't know how these encoders are made (are they optical?). May they fail this way? Before removing the front panel for troubleshooting, I wanted to ask the group for any advices. I could find one on ebay right now, but it would cost 50 USD + shipping. Thanks, Antonio I8IOV |
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3586A encoder question
The RPG (rotating pulse generator, i.e. the encoder) of one of my 3586A's doesn't work well. Clockwise it works well, counterclockwise it is erratic. May it be an issue in the encoder itself? I don't know how these encoders are made (are they optical?). May they fail this way? Before removing the front panel for troubleshooting, I wanted to ask the group for any advices. I could find one on ebay right now, but it would cost 50 USD + shipping.
Thanks, Antonio I8IOV |
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Re: HP-608A Repair
I don't have any of the 608s. I just remember repairing them when I worked as a calibration technician at Rockwell-Collins, Canada.
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Merchison On 2012-12-23 10:28 AM, Patrick Wong wrote:
It appears that there are several members with 608s responding to this string. |
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Re: S11 and S22 comparisons on 8753
On the 8752/8753/8720 etc., and pretty much all newer VNAs, even what you call "uncalibrated" is actually calibrated at the factory or at the service center when you send the analyzer for calibration. The problem is that you don't know what cables were used for the factory calibration. Hence, two analyzers that were calibrated with different cables will show different results giving the impression that the hardware is vastly different. I think, the 8510 was the last VNA which showed true uncorrected hardware performance when the instrument wasn't calibrated. And it was impressive!
This factory calibration is in a way similar to the user calibration, but the correction constants are saved in non volatile memory and protected with a jumper on the processor board. This then is the default state of the VNA when it powers up without a user calibration. A VNA with 35dB return loss is perfectly usable for most work. Realistically, the accuracy improvements for most work are very small as you get past that range. The log scale of the return loss measurement makes it easy to forget that going from 40 to 50 dB return loss requires heroic efforts for an improvement that is tiny in absolute terms. Vladan --- In hp_agilent_equipment@..., David Kirkby <david.kirkby@...> wrote: If you have not calibrated the VNA, then you are just seeing the...... Dave |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 23 December 2012 18:43, David McQuate <mcquate@...> wrote:
On "missing parts": some opens(mostly early, and I'm specificallyWas sort of like this though for 3.5 mm, not N as in this diagram? My own 3.5 mm kit does not have anything like this - the standards are self contained - no extra bits needed, and nowhere to fit anything. On "open / short combo": Neither standard has much length, so the twoTrue - they are convenient. There are 3 types of these 1) With just the open and short. 2) With open, short and load 3) With open, short, load and thru. Eiether way, one needs to have the data on the bits. If you read the 8753 manual, you will find the calibration kit it is deisgned to work with is the HP 85032B (as in the photo I showed). Any other cal kit has to be entered as a user calibration. Dave |
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Re: S11 and S22 comparisons on 8753
On "missing parts": some opens(mostly early, and I'm specifically
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thinking of APC 3.5 connectors) consisted of a body having no center conductor attached, plus an insertable center conductor on a plastic rod. Without the inserted center conductor, the characteristics of the "open" would not match the values assumed in the calibration calculations. On "open / short combo": Neither standard has much length, so the two can easily be packaged into one assembly, strictly for convenience (less likely to be misplaced because it is larger). There's no coupling whatsoever between the two ends. Dave On 12/23/2012 7:11 AM, Peter Bunge wrote:
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Clear Stream Technologies |
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Re: HP 3456a was Re: HP 3478A general questions
Thanks again, I've downloaded the manuals on most of the HP DMM's from that era. I'm now looking at the 3456 or 3457. I've got some prices on a cal and yes around $140 should do it for a NIST traceable cal plus shipping. Of the two meters, 3456 or 3457 which would be the smarter purchase ? The issues with the batteries I'm well aware of. My Tek 2465BDM lost it's Dallas chip internal battery. I've had to recal it after replacing the chip. A process that takes a while. It's accurate within about 0.1%. Good enough for a scope. The DMM is not anywhere near it's rated cal of 0.03% due to the data loss.
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In the interest of saving space I'm also looking at the HP 3468a or 3479a. I'm not seeing a major difference between the two except for perhaps some lower ranges on the 3478a. Any helpful info regarding those devices. If I can score a 3456a or 3457a for a reasonable price then I'll be heading that direction. At the moment I'm stuck doing projects with 4,000 count B&K meters and a 20,000 DMM on the Tek 2465 which is not in cal to it's spec. So my purchases will be pretty soon. I have a Fluke 8010 on the way which I'm sure will also need cal. Thanks, Jeff On 12/23/2012 7:08 AM, marvgozum wrote:
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Re: HP-608A Repair
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----- Original Message -----
From: "Patrick Wong" <patwong3@...> To: <hp_agilent_equipment@...> Sent: Sunday, December 23, 2012 9:35 AM Subject: [hp_agilent_equipment] Re: HP-608A Repair Hi Richard,It is very odd. I need to give this some thought. The only think that comes to mind immediately is that the monitor may be affected by harmonics that do not affect the other instruments. I would also check the output at lower levels to see if the difference is affected by the position of the attenuator probe. -- Richard Knoppow Los Angeles WB6KBL dickburk@... |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 23 December 2012 17:09, David Kirkby <david.kirkby@...> wrote:
I meant "gold plated metal", not "gold played meter" Dave |
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Re: HP 3456a was Re: HP 3478A general questions
I treat buying gear much like a trip to Vegas, I save up a few dollars and enjoy myself knowing full well that I'm wasting money. In the end it's not what you pay, it's how much you enjoy the experience. So if I pay too much for a piece of gear and it turns out to meet all my expectations..then money well spent. If on the other hand I get a lemon and have to sink more cash in to it..then it was a bad trip. It's often why I don't mind paying more for auctions that show proof of life. Better still proof of accuracy. I paid too much for my Tek 2465BDM, however it's in mint condition, works perfectly and I use it just about everyday. Money well spent.
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Thanks, Jeff On 12/23/2012 10:20 AM, Bob Albert wrote:
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Re: HP 3456a was Re: HP 3478A general questions
Bob Albert
Thanks, I guess I will have to just keep looking. For $50 I would love to have one of these, or one of its sister units. And being in Los Angeles, there is always a likelihood I can find one that doesn't have to be shipped.
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Bob --- On Sun, 12/23/12, marvgozum <mxg003@...> wrote:
From: marvgozum <mxg003@...> |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 23 December 2012 15:11, Peter Bunge <bunge@...> wrote:
Merry Christmas all!Merry Christmas My friends and I have been comparing what we see from the S Parameter Test Set on the two ports. These tests are with the VNA uncalibrated and with proper opens or shorts (even from APC7 cal kits).If you have not calibrated the VNA, then you are just seeing the uncorrect performance, and the fact that varies is no surprise. In fact, I'm a bit surprised you managed to get 35 dB uncorrected. There are a large number of systematic errors in a VNA. It does not matter, as the whole idea of the error correction is to remove those. I get very similar results using the same S Parameter Test Set on an HP8753B and an HP8753C so the curve shape is caused by the test set not the VNA.Don't worry about it. Typically we see one port 10 dB better and flatter than the other.It is only important once calibrated. The calibration removes the systematic errors. p.s. the cal kit discussion was very informative and timely. I still don't understand the comment (that was later corrected) about the open usually missing a part. My friend's Type N cal kit does not have extra parts for the open.It depends on what cal kit he has, but on for example and 85032B you will often see something like this: The small bit of gold played meter you see, is designed to increase the diamteer of the last few mm of the pin, so it is 50 Ohms, and not higher. If you think about it, to get as near as possible to an open, you want to have a 50 Ohm line that is cut off sharp at the end. Now consider what an open N male looks like. The male pin is thicker at the bottom. That bits makes 50 Ohm transmission line. Then the diameter is reduced for about 5 mm, so it can go in the female. That will not make a 50 Ohm transmission line, but a higher impedance line, due to the formula Zo=60 log(d_outer/d_inner) So an open N plug is not as close as possible to an open. Does that make sense? Hence the female part has an extender. I would add it is possible to calibrate a VNA with an open N connector without that. Accuracy suffers a bit, but that technique is used in Agilent's portable VNA's. A better bet is an shielded N. But again you need to know the paramters. Also I have seen an open/short combo advertised and wonder if this comes apart to use the open??? I have not used one and find the concept of one end a short (OK) and the other an open (how?) confusing.If you see an open/short advertised you MUST make sure you have the paramters on it. It will have an offset in ps, and three capacitance coefficents C0, C1, C2 and C3. You should then enter them in your VNA. If you don't have that information, the kit is effectivly useless. The short will have an offset too. The short might also have inductance paramters L0, L1, L2, and L3, but you can't enter them in the 8753 series, so don't worry about them. They are not important for the the frequency range of an 8753. I hope that makes a bit more sence. Dave |
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Re: S11 and S22 comparisons on 8753
J. Forster
A 30 dB return loss is nothing to sneeze at.
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-John ===================== Correction! We are seeing this with a good load attached, no calibration. |
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