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HP 478A Thermistor Sensor. Input return loss and matching 6
In the last few weeks, I've had my old HP 432A power meter on the bench along with its 478A thermistor sensor. I normally only use it about once a year to check the 1mW (50 MHz) reference on another power meter. However, I've spent a bit more time looking at the 478A sensor and wondered if it was worth sharing some of the knowledge gained and also some of the options for reducing the measurement uncertainty compared to using a standard sensor at 50 MHz. I've looked at the input match, the efficiency and also at how the 478A has had some changes internally over the years. One obvious option to improve the input match at 50 MHz is to buy a special version with option H75 or option H76. These are probably quite rare and expensive. Another option is to improve the input match of a standard sensor by adding a low loss (external) matching section inline with the standard sensor. I have done this and have achieved good results. I'll show the design process and test results in this thread. The standard sensor has a fairly grim spec for input VSWR at 50 MHz of about 1.3:1. However, it shouldn't be this poor at 50 MHz if you look at what is inside the sensor and model the VSWR. In theory, an older version of the 478A (like mine) should manage a VSWR of about 1.07:1 at 50 MHz. The later versions might be closer to 1.05:1 at 50 MHz. So in this sense, there probably isn't much point trying to improve the match if the aim is to measure a 1mW reference from a typical HP power meter. This is because the source VSWR of the 1mW reference is likely to be much lower than its spec of about 1.06:1. So the mismatch uncertainty should be negligible. Only a calibration house should really be concerned here, but I thought I would have a go at improving my sensor anyway. The following posts show the thought process and the modelling and the test results. I've attached a VSWR plot of the input VSWR of an early HP 478A sensor. This was taken with a lab VNA set to a really slow sweep time of about 20 seconds, although slowing the sweep time from less than 1 second to 20 seconds didn't seem to make much difference. You can see there is a kink in the VSWR at 50 MHz and this has always bugged me because it causes a bump in the efficiency across about 40-60 MHz. I've lived with this 'bump' issue ever since I first got this sensor back in the 1990s. But now I've managed to get rid of it and I'll show what causes it and how to upgrade an older sensor like mine to get rid of it. -- Regards Jeremy
Started by jmr @ · Most recent @
HP8757A Display Problem (Scalar Network Analyzer) 2
Hi all, I have a HP8757A scalar network analyzer with a display problem which has appeared after some 6 months of no use. It was previously working just fine, with a HP8350B sweep generator and the 10MHz - 20GHz plug-in. What happens is that on switch-on, it goes thru the self-test and then reverts to a display which seems to contain some correct information such as frequency span, key button names (at the right), and a 'noisy' scan waveform (as expected) - BUT the display refresh is very slow and is well off-centre - it is clearly cycling through the 4 'display channels sources' but it is nearly unreadable (certainly unusable). I have another 8757A which I use with another sweeper which works well, and by using this as a 'test reference' I can determine which buttons to the right of the screen to use to perform some tests. In this way, I have called up the test pattern display (SYSTEM -> MORE -> SERVICE -> DISPLAY -> TEST PATTERN) and this generates the wanted test pattern BUT this is also well off-centre and refreshed slowly. I have checked the error-code LEDs (removed the top cover of course) and they are all off (zero) after switch-on or after "PRESET" which indicates no error found, and also checked the +15V, -15V and +5V on the small power board with the fuses. The +105V rail there is also correct. This problem is independent of whether the 8350B sweeper is on or off, and if it is on the PRESET button initializes both the 8757 and the 8350 as it should. I have compared the problem unit with the working unit and the basic functionality would appear to be present. I am wondering if the battery on the CPU board (backing up some constants?) could be a reason, but I doubt it - I can replace this tomorrow if I think it might be. I know that the refresh frequency of the display will be lower with the more channels that are being scanned (A, B, C, R) but this does not appear to change the problem on the unit that I am dealing with. For what it's worth, I have a comprehensive workshop and lab at home and I am used to working with both microprocessor designs and (more so) with microwave / ATV designs. I have read the service manual and operating manual but with so many pages and different references I am not sure where I should be looking. Would anyone here have a good idea of where the problem could be? My sincere thanks in advance.
Started by Trevor Gale @ · Most recent @
HP 8566B repair 9
Hello everyone. Suddenly my spectrum analyzer (HP 8566B) has the following problems: the low band signal is about 40 dB lower than it should be. The high band has stopped working: the various bands no longer appear on the screen, but a single band similar to the low band and the signal is completely absent! I strongly suspect that the YTX oscillator is dead or almost dead! Does anyone have any ideas about this? Thanks. Images: HP8566B and output at first LO connector. IMG_20250504_121626.jpg (89.93 kB, 1000x750 - viewed 13 times.) IMG_20250504_121605.jpg (122 kB, 1000x750 - viewed 16 times.)
Started by gsl@... @ · Most recent @
Recap 6205B
I am seeking replacements or substitutes for these caps: C10 HP p/n 0180-1852 x2 C14 HP p/n 0180-1888 x2 C20 HP p/n 0180-1851 x2 I have tried a variety of cobbled together solutions and they have not worked. I do not want to scrap this device but I am out of ideas. Thanks -- Joe White KW4YW
Started by Joe White @
1 mw - 0dbm lab calibration 124
Hi all Regarding 1 mw lab calibration I am looking for comparisons between the old and trusted HP 432A the replacement N 432A and the Tegam 1830A and I was wondering if anyone hear Can give any feedback on the Tegam 1830A compared to the new N 432A Also is there a report comparing the 3 meters Regards Paul
Started by Paul Bicknell @ · Most recent @
how to convert HP83711B to 83712B!
Hi folks, I have converted my HP83711B signal generator into an HP83712B and have added options. See here how I did it: /g/HP-Agilent-Keysight-equipment/files/All%20HP,%20Agilent%20and%20Keysight%20instruments%20in%20folders%20by%20part%20numbers/A%2080000%20to%2089999/83711B%20and%2083712B%2020GHz%20signal%20generators/HP83711B_to_HP83712B.pdf Maybe useful to someone or just fun to read. Tom
Started by tom_iphi @
HP DC Power Supply modification 2
Hi to all, I am looking for a modification for the following PSU to ioncrease the voltage to 13.8V , any ideas? HP DPS-1400CB A PWS 1400W HSTNS-PD43 754383-001 DL360 G9 DL380 G9 LFF Thank you all Nick SV1VS
Started by NICK K. PLUMIDAKIS @ · Most recent @
Looking for service manual/schematic for early E3611A DC Power Supply 4
Hi, I'm currently repairing an early HP branded model E3611A DC Power Supply to give to a friend, but the schematic from the usual online sources is for later models that differ in some parts (notably around the area I am trying to repair....) Does anyone have a copy of the service manual for early HP units they can share? I just need the schematic and parts listing in particular. Thanks! Jared
Started by Jared Cabot @ · Most recent @
5334A replacement capacitor
I need a replacement or substitute for A1C19 (0180-2991), Sprague 67D398H020JL5A. Mine let go in spectacular fashion, magic smoke, magic goo, pungent atmosphere. Thanks -- Joe White KW4YW
Started by Joe White @
Question: Is there a correct* way to get an HP T141/855X Spectrum Analyzer to sweep logarithmically? (* as in: HP provided specific instructions/equipment for this) 3
(Bear with me, I¡¯m still learning how to use this platform) I¡¯m primarily interested in obtaining logarithmic sweeps/bode plots while using my 8556A audio frequency plugin and 8570A Storage Normalizer specifically for audio amp, loudspeaker, and crossover characterizations. Its native linear sweep/plotting makes it incredibly difficult to distinguish things at the low end of the frequency range; effectively prohibiting one from gathering useful data from a single 20Hz - 20KHz pass (I instead have to break up the single measurement into multiple, across smaller ranges¡­ a very inconvenient endeavor). Did HP ever publish any sort of instructions or app notes that address this? Did they produce any accessories/equipment specific for this? I understand there were logarithmic converters available for XY plotters, but I¡¯ve yet to get any confirmation as to whether or not they would be best applicable to my specific needs, and/or how they would work in conjunction with the 8570 normalizer. Thoughts? Recommendations? Thanks-
Started by Petejalley@... @ · Most recent @
HP3582a problem no chanel 2 4
Hello, I recently purchased an HP3582A, and I'm encountering a problem with channel B. It's constantly in overload and always displays a saturated spectral line, even with nothing connected. Channel A seems to be working fine. To diagnose the issue, I swapped the cards for channels A and B, and I found that both cards function correctly, but only when plugged into slot channel A. I also swapped 4 digital filter components , but the problem persists. Is there anyone who could guide my investigation? Thanks Patrick
Started by edipsoft@... @ · Most recent @
ftp.agilent.com tar-file on archive.org 7
The Internet Archive has what appears to be a snapshot of ftp.agilent.com from 2014. Link is https://archive.org/download/ftp.agilent.com. The file is rather large (317GB) and an attempt to download failed after approximately 220GB. I don't want to blow my monthly data plan and thus decided to wait a little before attempting it again. The Internet Archive allows the download of individual files from the tar-ball, but I'd rather have a replica of the whole site to browse and explore locally. Has anyone successfully downloaded this tar file? Don't want to waste time and bandwidth if the file is known to have issues. Thank you, Wolfgang KI7PFX
Started by Wolfgang Schraml @ · Most recent @
Twelve(+/-) bins of original HP/Agilent manuals free for pickup in San Diego 7
I have approximately twelve plastic storage bins (22" x 15" x 12") of test and measurement related manuals that are surplus to my needs. The vast majority of them are HP/Agilent manuals (e.g. scopes, analyzers, generators, and many, many more), and are predominantly operating and service manuals. All are original hardcopy in original binders, and are in very good to excellent condition. There is also some software on 3-1/2" floppy disks. I'd like them to go to someone who can use them, and hopefully make scans and copies of them for the benefit of all. I do not want to have to pack them and mail them, so I'd very much prefer that they be picked up here in San Diego. I'm also willing to drive a reasonable distance to meet whoever wants to take them all. Any interest? Thanks, Stan
Started by Stan @ · Most recent @
HP 432B display 6
Hi all I have managed to find a HP 432B unfortunately the digital display is shot Has anyone got a spare working display alternatively a non worker? Also has any one successfully repaired a display Paul located UK
Started by Paul Bicknell @ · Most recent @
5334A part reference 9
What is the replacement for part 1820-3639, IC-8-bit-4K ROM? I am also seeking option 010, XTAL oscillator for this device. -- Joe White KW4YW
Started by Joe White @ · Most recent @
HP E6380A - 8935 Frequency range
A question on the HP E6380A - 8935 test set. Does that test set allow you to test 1.2 GHz analog FM equipment? The set mentions the range from 1.7 to 2.0 GHz and then 400 kHz to 1 GHz from what I read. So is there some kind of gap where say you cannot test a radio for TX/RX at 1288 MHz? Thanks - Sig
Started by Siegmund Souza @
FS 8660C Keyboard-Logic assembly
HP Group, FS, Keyboard, with logic assembly attached, removed from 8660C. Knobs, keys all intact. Was working when removed. $40.00 shipped to your door, US- L48. Gary WA2OMY
Started by Gary Hitchner @
HP 10525H Logic Probe 2
Hi , I need the service manual of the HP Logic Probe 10525H . Many thanks in advance . Best regards Maurizio IZ1MDJ in Turin
Started by Maurizio IZ1MDJ @ · Most recent @
HP Basic for Windows 6.33, printed documentation 20
I have found the installation image for HP Basic for Windows 6.33 on the internet archive From the images in the archive it looks as though there were a number of printed manuals that were supplied with the package I am especially interested in the Installing and Using and User's manual Does anyone have access to these documents in .pdf from? Peter
Started by Peter Brown @ · Most recent @
Several problems with Agilent 54810 15
Hello, I am asking you to move forward on several issues. First this oscilloscope did not start at all. I found the failure by dismounting the main acquisition board which had a capacitor on the burnt-out, short-cuircuit -12v. Now power supply OK, it starts. All voltages controlled. Good! Of course on 2nd failure, the disc is completely mechanically out of order. To be see later so disconnected at this time. Now on the outside screen, i have the bios and its errors. I have the impression that the retro lighting does not work (in theory powered by 12v and give HT.) LCD screen black. I don¡¯t think there is a feature that starts the retro backlight later. Can you confirm that it simply starts basicly when power on. As, there is no keyboard, I wanted to plug one.It ¡¯s a 5-pin din on an Atlas 757 PCI3 board. So I adapted the cable of a PS2 keyboard (cut + welded a din). It initializes (flash of the 3 leds at power on) but after impossible to communicate. So is the keyboard accounting AT or XT, it¡¯s not the same protocol ? Somebody have made the test? So for that i am blocked for the bios Thanks for your answers cdt
Started by Gerard @ · Most recent @
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