hybridfree/eevblog-posts huggingface dataset:
HP745A switch circuit - frustrating square wave generator problem - Page 1
Forum section: electronics / repair

author: tonycox01
author_rank: Contributor
timestamp: July 19, 2020, 08:51:23 pm
content: Hi,I'm trying to fix up an HP745A AC calibrator. The main square wave generator is an astable multivibrator that feeds a 1kHz square wave in to a bistable multivibrator to produce 30v p-p 500Hz square wave. See first pic. The astable section produces a nice 1Khz 29v p-p square wave but the bistable section generates nothing at all.It is a frustrating problem. I replaced the three transistors (Q3-5) as they were only 2N3904's and also the diodes. Initially I found that the -25V rail was not working properly but that is fixed now and checked as working. The +/-15v rail, the -25v and +22v rails all seem to be working fine - although the +22v is a little high at nearly +26v.If I put a scope both sides of CR2 I see the incoming +/- pulses from C4 on one side and only negative rectified pulses on the other side (see 2nd pic) - which is what Id expect. But if I do the same to CR1 I see the incoming +/- pulses on one side but nothing at all on the other side (see 3rd pic). Both diodes are new so I know they are good.I'm struggling to understand how these rectified pulses disappear for CR1.Any advice/help would be very welcome!many thanksTony

author: duak
author_rank: Super Contributor
timestamp: July 19, 2020, 10:24:59 pm
content: I think there won't be any pulses on the anode of CR1 if Q4 is turned on. What are the voltages on the collectors and bases of Q3 & Q4?I see from your schematic that CR1 & CR2 might be 1N645. I don't know if this is correct and wonder why the designer chose these parts as they appear to be rectifiers rather than signal diodes. If so, there may be more to this circuit than meets the eye. ie., the resistor and capacitor values might be fairly critical.The circuit is not symmetrical as there is a buffer that brings back some current (through R16). Have you checked Q5 and the parts around it?

author: tonycox01
author_rank: Contributor
timestamp: July 21, 2020, 08:59:01 am
content: Thanks Duak.If Q4 was turned on it would have to be all the time to see no pulses and in which case I should see some output which I do not. I'll check the base voltages however to be sure.CR1/2 are rectifiers according to the parts list and I replaced them with similar spec 1N4002's. I don't think these are the problem as the originals checked OK too. I agree that this circuit seems to be doing more than is obvious. I thought about disconnecting the buffer stage to see if the core multivibrator circuit itself still functions.I really am running out of ideas - and parts to replace....thanksTony
HP8116a   eprom content - Page 1
Forum section: electronics / repair

author: xantia_99
author_rank: Contributor
timestamp: October 06, 2024, 01:28:56 pm
content: HiI got HP 8116a I got some minor and some severe problem with it.I do a repair och upgrade of my 8116a. I also want to upgrade the Eprom content.Serial number 2334G02751.with a A3 microprocessor board 08116-66503In the update documentation is says it should in Eprom content versionU5 08116-10021U6 08116-10022U7 08116-10023U8 08116-10024U9 08116-10025U38 08116-10026Now I got an earlier version, I found the same which is possible to down load from ko4bb.com.So can anyone help me and the best would be to download it to k04bb.comRegardsXantia_99
HP83630B EPROM firmware - Page 1
Forum section: electronics / repair

author: Drirr
author_rank: Regular Contributor
timestamp: February 24, 2020, 10:18:27 am
content: Hi,Does anybody have HP83630B firmware? There are two EPROMs on PC board.ThanksDavid

author: DominiqueB
author_rank: Newbie
timestamp: March 19, 2020, 02:24:17 pm
content: Hi avid,I have one HP 83630L opened on my bench. I do not know if the Firmware is identical for the B and the L model. If you think it's the same, I can send you the image of the L Firmware.Best regards,DominiqueB F4HIJ
HP8485A power sensor reads erratically - Page 1
Forum section: electronics / repair

author: alan.bain
author_rank: Regular Contributor
timestamp: December 22, 2024, 02:28:30 pm
content: I've got a working HP 8485A power sensor and another one which I suspect is dead, but am curious as to the failure mode. Most of the dead one I have seen won't zero. This one zeros fine and can be calibrated but the reading is unstable. It's easiest to see on an analogue meter like the 435 the needle wobbles significantly (rendering it unusable of course).Is this a known failure mode? I'm aware they are basically unrepairable!Alan

author: Stray Electron
author_rank: Super Contributor
timestamp: December 22, 2024, 08:35:26 pm
content: Are you sure that the problem isn't in the cable assembly? The cable for my HP Power Meter is gimpy and sometimes works and sometimes doesn't. And it acts the same with all of the sensors that I own.I don't use the meter much so I've never tried to located the bad spot in the cable or to fix it.

author: alan.bain
author_rank: Regular Contributor
timestamp: December 23, 2024, 12:00:34 am
content: Good thought. I have two other cables so will try them.Alan
HP8558B Versus HP182T Sweep Fail. - Page 1
Forum section: electronics / repair

author: hcapela
author_rank: Contributor
timestamp: February 19, 2022, 12:21:40 am
content: Good year 2022 without the accursed bug.Well there everyoneIn April 2019 my HP8558B decided to let it do the sweep Fig0 , I found that only with external sweep it worked, it was on the waiting list for a better analysis, however I was around the HP8116A and with external help I got there (well there Markl).In December 2021, in a visual inspection of the HP8558B plugin, I found that some of the contacts (fingers) of the 4 switches were loose, and I thought it was here, and the novel that I summarize below beganPreliminary Notes: Understanding certain details implies access to the HP182T/C Service Manual.I urge HP experts to speak up.1st 2019 I lost the HP8558B scan Fig02nd 2021 I considered that the failure was due to lack of contact finger in the SW. Fig1 and Fig1.1 , ward work.3rd mechanically fixing the fingers of the SW Fig24th Malfunction remains☹5th Test of the switches all OK, with the help of a kit adapted from the IC card HP10529-20005 Fig3 and fig4.6th Why not use my HP180C+HP1802 and HP1821A that is stopped !! fig5 , because I haven't used it before ☹Test with the Main Frame HP180C and the HP8558B, after de-rusting the switches and adjusting, voilá HP8558B OK!!7th Use 182T with HP1801 and HP1821 OFF, I confirm the failure is in the HP182T.8th All voltages on HP182T OK.9th Summary measurement of transistor and diode junctions (all?) OK10º Measurement of HT -3KV †† and 19KV †† , result +-2.9 and +- 18KV, OK10th Use of two 1V 100 Hz sine wave generators for input on the HP1801A and the EXT INPUT sweep on the 180C11º Results in a distorted Lissajous image by pressing FIND BEAM Fig612th With Intensity CW almost at MAX. clear image Lissajous Fig713th In sweep INT values of UNBLANKING GATE board A7 pin14 is -0.2V should be -0.7V14th Output on board A7 ALT TRIGGER pin13 for Plug-in not detected?15th UNBLANKING SIGNAL output values also in A7 pin w4, is between +20 and +75V when it should be between +42 and +92V DC values, and is not a square signal.16th I'm in a fish situation with is tail in the mouth.Best regardsBem Hajam
HP182T Sweep Fail. - Page 1
Forum section: electronics / repair

author: hcapela
author_rank: Contributor
timestamp: February 18, 2022, 09:50:32 pm
content: HP8558B Versus HP182T Sweep Fail.Good year 2022 without the accursed bug.Well there everyoneIn April 2019 my HP8558B decided to let it do the sweep Fig0 , I found that only with external sweep it worked, it was on the waiting list for a better analysis, however I was around the HP8116A and with external help I got there (well there Markl).In December 2021, in a visual inspection of the HP8558B plugin, I found that some of the contacts (fingers) of the 4 switches were loose, and I thought it was here, and the novel that I summarize below beganPreliminary Notes: Understanding certain details implies access to the HP182T/C Service Manual.I urge HP experts to speak up.1st 2019 I lost the HP8558B scan Fig02nd 2021 I considered that the failure was due to lack of contact finger in the SW. Fig1 and Fig1.1 , ward work.3rd mechanically fixing the fingers of the SW Fig24th Malfunction remains☹5th Test of the switches all OK, with the help of a kit adapted from the IC card HP10529-20005 Fig3 and fig4.6th Why not use my HP180C+HP1802 and HP1821A that is stopped !! fig5 , because I haven't used it before ☹Test with the Main Frame HP180C and the HP8558B, after de-rusting the switches and adjusting, voilá HP8558B OK!!7th Use 182T with HP1801 and HP1821 OFF, I confirm the failure is in the HP182T.8th All voltages on HP182T OK.9th Summary measurement of transistor and diode junctions (all?) OK10º Measurement of HT -3KV †† and 19KV †† , result +-2.9 and +- 18KV, OK10th Use of two 1V 100 Hz sine wave generators for input on the HP1801A and the EXT INPUT sweep on the 180C11º Results in a distorted Lissajous image by pressing FIND BEAM Fig612th With Intensity CW almost at MAX. clear image Lissajous Fig713th In sweep INT values of UNBLANKING GATE board A7 pin14 is -0.2V should be -0.7V14th Output on board A7 ALT TRIGGER pin13 for Plug-in not detected?15th UNBLANKING SIGNAL output values also in A7 pin w4, is between +20 and +75V when it should be between +42 and +92V DC values, and is not a square signal.16th I'm in a fish situation with is tail in the mouth.Best regardsBem Hajam
HP8559A Vertical Offset Problem - Page 1
Forum section: electronics / repair

author: Gregory
author_rank: Regular Contributor
timestamp: December 11, 2021, 02:39:07 am
content: Hello guys! I scored a HP8559A spectrum analyzer, but I'm unable to make the calibration procedure.One of the steps says to use VERT POSN adjust to place the trace at the bottom of the display.But it seems my trace is offset upwards, I can't get it to the bottom.Now I'm trying to understand if it is a problem on the vertical amplifier or before it, like in the log/lin amplifiersI recorded a video explaining the problem
HP8563E On the way. - Page 1
Forum section: electronics / repair

author: djsb
author_rank: Super Contributor
timestamp: October 20, 2021, 03:29:45 pm
content: I've just gone and done it again. Just bought a HP8563E spectrum analyser from the same seller off that auction site. This one is for spares or repair as the screen is blank. Paid £130 for it including postage.As the HP8563E and HP8564E share some (or a lot) of the same parts, I'm hoping to get at least ONE (or maybe both if I'm lucky) working properly. I've also ordered an ArtekManual package fromhttps://artekmanuals.com/manuals/hp-manuals/And I've joined the HP/Agilent/Keysight test equipment group.io group to hopefully get some assistance in the repairs.https://groups.io/g/HP-Agilent-Keysight-equipmentThis is probably going to take me a couple of years (or more) to complete. Hope I'm successful.

author: rfclown
author_rank: Frequent Contributor
timestamp: October 25, 2021, 01:59:32 am
content: Quote from: djsb on October 20, 2021, 03:29:45 pmThat is so cheap. My HP8562A weights a ton. Shipping couldn't have been cheap. They gave it away. (unless I'm not figuring £ to $US correctly)
HP8563E replacement for noisy cooling fan-Which one? - Page 1
Forum section: electronics / repair

author: djsb
author_rank: Super Contributor
timestamp: May 14, 2023, 09:08:30 am
content: The power supply cooling fan on my HP8563E Spectrum Analyser is noisy, and I would like to replace it before I button up the case.Has anyone replaced theirs and if so which one did you choose? Which size is it, and where can I find a replacement? Thanks.David.
HP8563E SIMMCONN LABS NewScope-6 final adjustment procedure help please. - Page 1
Forum section: electronics / repair

author: djsb
author_rank: Super Contributor
timestamp: April 28, 2023, 08:40:40 am
content: I'm in the final stages of adjusting my NewScope-6 VGA installation on my HP8563E spectrum analyser. The instructions are as followsQuoteHere is a brief email exchangeQuoteAndQuoteI have attached the 2 pictures of the screen on the HP8563E that I took during my first attempt at the adjustment. I'm wondering if anyone else has successfully done this adjustment procedure, and can you explain to me how I can change the reference level so that the modulating waveform (400Hz or 1KHz) fills the whole screen. I can post additional info from the service manual if needed, or take additional photos from a second and any subsequent attempts later. Thanks.
HP8564E Spectrum Analyser on the way. - Page 1
Forum section: electronics / repair

author: djsb
author_rank: Super Contributor
timestamp: October 20, 2021, 10:07:13 am
content: I've got a HP8564E Spectrum Analyser (9KHz to 40GHz) on the way. It has an attenuator fault but works on the -20db range and passes all the start up checks (according to the auction blurb). I'm hoping I can eventually fix it. Cost me £630 including postage. Downloaded the service manual and I've watched this videoSo I'm hoping the HP8564E has a similar layout. May do a gradual recapping job whilst I try to find the attenuator problem. Wish me luck as I may need it.

author: tggzzz
author_rank: Super Contributor
timestamp: October 20, 2021, 10:28:30 am
content: This one?https://www.ebay.co.uk/itm/115054048559But that shows the single bid price to be £750?FWIW, I bought a metcal iron from that purchaser. Well packed, as described

author: djsb
author_rank: Super Contributor
timestamp: October 20, 2021, 11:27:13 am
content: Yes. I put in a cheeky offer and the seller made a counter offer which I accepted. Reconned that repairs and/or calibration would cost a fair bit so thought I'd put in a lower offer. After all I'm taking the risk of it being a large doorstop if I can't fix it. It is at least usable with the -20db attenuator.

author: tggzzz
author_rank: Super Contributor
timestamp: October 20, 2021, 12:07:41 pm
content: Quote from: djsb on October 20, 2021, 11:27:13 amThat sounds reasonable. I was tempted, but already have a Tek 492 and HP8562B, and insufficient space for anotherThe 8565b I bought in a "general auction", condition unknown except for a photo that showed it was in cosmetically good condition. It turned out that it was allegedly from a bankruptcy sale, and was in good working order. I have subsequently replaced the PSU delayed action smoke generators (RIFAs), finding that the only ones that would fit were identical new types. They should last me out.So, a "big" risk, but I could tolerate "losing" £350 - which I haven't.Good things come to those that wait; I hope yours matches expectations.BTW, internally they are a mechanical marvel, and you can see why they cost so much! There are a couple of pictures herehttps://www.eevblog.com/forum/testgear/hp-vs-tektronics-design-philosophies/msg3153112/#msg3153112which give a flavour of why I don't want to disassemble them more often than necessary!
HP8566b Bandwidth Adjustment - Page 1
Forum section: electronics / repair

author: tkamiya
author_rank: Super Contributor
timestamp: November 29, 2022, 09:58:48 pm
content: As part of alignment procedure, display section of HP8566B spectrum analyzer has to be adjusted. Filter Bandwidth adjustment is done as part of the display section. I recall seeing *somewhere* chain of filter has to be bypassed all except for one that is tweaked, so that they are isolated. I spent few days looking for a documentation or a web page explaining how this is done, but alas I cannot find one. Can anyone please point me to the right direction?

author: davidwenrich
author_rank: Contributor
timestamp: January 30, 2023, 03:21:29 am
content: Did you ever find a solution for this question? I have a complete tests and adjustment manual set. I remember reading about this procedure, I believe construction of bypass filters is required, of which parts and schematics for building them is included.
HP8568B Marker measurement error. - Page 1
Forum section: electronics / repair

author: Johnny10
author_rank: Frequent Contributor
timestamp: October 11, 2019, 09:53:59 am
content: I have an 8568B Spectrum analyzer that seems to work displaying frequency.However when using marker to find that frequency I get an erroneous number.Example: 760MHz signal is measured as 440MHz.What circuitry controls these measurements?

author: xwarp
author_rank: Frequent Contributor
timestamp: October 11, 2019, 09:25:53 pm
content: Can you do a short video showing what you are talking about?
HP8590A repair... - Page 1
Forum section: electronics / repair

author: Oberon
author_rank: Contributor
timestamp: May 01, 2025, 09:08:00 am
content: Greetings! The problem is that I have a Spectrum analyzer HP 8590A, Ser. 2816A02744, which I really want to repair. Unfortunately, I can't find the circuit diagram of the A7 partner 08590-60001 board anywhere. In many of the files that I managed to find, there is no such card with this exact number anywhere. I want to ask the group for help in finding documentation and diagrams for my device, and not for other devices. With great respect to you and your business, Alex.

author: Oberon
author_rank: Contributor
timestamp: July 20, 2025, 04:50:56 pm
content: I am glad to welcome you! Colleagues, I fixed my HP8590a!! To do this, I had to buy a second converter. I changed the faulty one to the purchased one and everything worked! Replacing the HP 1GS1-4210 in TO72 transistor with a BFW30, as described in the link:http://f1chf.free.fr/F5DQK/2_Amplis_RF_amplifiers/432%20MHz/HP8970b%20erreur%2018.pdf, did not lead to success, as I could not set the frequency to the required value. Thank you all for your attention! Here is my screen with display cal data:

author: Oberon
author_rank: Contributor
timestamp: July 20, 2025, 04:52:02 pm
content: Display cal data^

author: Oberon
author_rank: Contributor
timestamp: July 20, 2025, 04:55:23 pm
content: Colleagues! please tell me if everything is fine with the device with these calibrations?? Sincerely, Alex!
HP8590A Spectrum Analizer repair A5 - Page 1
Forum section: electronics / repair

author: Oberon
author_rank: Contributor
timestamp: April 07, 2025, 08:51:41 pm
content: Good time! Colleagues, I ask for your help. The HP8590 ser. 2816A02744 device is available. My second mixer (A5 Second converter 08950-600048) stopped working. As I found out, the contact in the HP40156 1GS1 4210 transistor was broken. I could not find an analogue for this labeling. Can you tell me how I can replace the specified transistor from modern samples? I understand that HP labeling differs from the generally accepted labeling of transistors worldwide. I would be very grateful for the information. Sincerely, Alex, R3DCF.

author: Oberon
author_rank: Contributor
timestamp: April 10, 2025, 07:30:34 am
content: I ordered transistors for the restoration of 2N2857 and 2N5031 in TO-72 cases and according to the parameters of the BFW30 and KT399A. I will try to restore A3 as soon as the package arrives. We're waiting.

author: Oberon
author_rank: Contributor
timestamp: April 10, 2025, 07:32:55 am
content: Unfortunately, I have not found any information about the 1GS1 4210 transistor anywhere..... very sad!

author: Oberon
author_rank: Contributor
timestamp: April 28, 2025, 09:13:23 am
content: Colleagues! Good time! Unfortunately, no one answered... Now I'm asking for help with something else. I need a diagram of the parts and the schematic diagram of the 09590-60001 Analog Interface board (A-2739-53). I kindly ask for your help in finding a schematic diagram for this board. I have an old device and I want to restore it! With respect, to the whole society, Alex.
HP8591E phase noise question - Page 1
Forum section: electronics / repair

author: sp9bsl
author_rank: Contributor
timestamp: July 07, 2022, 09:30:20 pm
content: Hi all,I have HP8591E analyser and while comparing it to some newer equipment like Siglent SSA3021X, I noticed somewhat high side noise of my HP. I can't find any screenschoot of such measurement one of the HP8590E series so, I'd like to ask here. This is measurement of CAL output (300MHz) available at the front panel. Cal signal was measured also with mentioned Siglent and it is much cleaner, about -90dBc at 2kHz offset from the carrier (same RBW, same VBW and span).I unplugged the SMB connector from third converter (321.4 input) and signal measured on Siglent has exactly the same shape and 2kHz dBc value I see on HP. The 600MHz output to tripler has side noise about -90dBc at 2kHz offset - I think hits bottom limit of Siglent.My analyser passes all calibration routines with no errors. HP spec says about side noise: <-65dBc at 30kHz so technically ok but... I'd be happy to see such measurement from another user.RegardsSlawek

author: Bud
author_rank: Super Contributor
timestamp: July 08, 2022, 03:26:21 am
content: Here is a shot from my 8594E.

author: sp9bsl
author_rank: Contributor
timestamp: July 08, 2022, 06:30:54 am
content: Hi Bud,Thank you! Looks close to mine. I think the few dB difference around 1kHz (and overall slight different "skirt") might be because of different (better) YIG in your HP.
HP8593A  attenuator fail - Page 1
Forum section: electronics / repair

author: maxniz
author_rank: Contributor
timestamp: July 23, 2025, 05:30:33 pm
content: Good evening everyone, I'm having a problem with the attenuator of my HP8593A. There's a short circuit, i must to disconnet the module for turn on the SA . i have found two diodes in cc and i don't know what thet exacly are!! it's marked: 33321RV 5086-7776 (look at the photos) I look at everywhere bau i can't find the wiring diagram. Could someone please tell me where to find it? The components, except for the 2003, have strange markings. . Thanks.

author: VK5RC
author_rank: Unknown
timestamp: July 24, 2025, 02:53:27 am
content: While I can't be sure of the specifics for that attenuator - but like a lot of HP gear they tended to repeat a successful strategy.If you are not already aware The Signal Path youtube channel has some great high level test gear repair including an HP high frequency attenuator - hope this is helpfulhttps://youtu.be/IQZxvtEn4T8?si=sU8sPsl9ABtZRVYZ

author: maxniz
author_rank: Contributor
timestamp: July 24, 2025, 09:38:53 am
content: Thanks, great video but it doesn't help me with the electronic components... only the mechanical ones and to fix it I need the wiring diagram of the second board mentioned.

author: Hamelec
author_rank: Regular Contributor
timestamp: July 25, 2025, 10:40:27 pm
content: --
HP8593A  fail - Page 1
Forum section: electronics / repair

author: maxniz
author_rank: Contributor
timestamp: July 21, 2025, 02:13:52 pm
content: Good morning everyone, I've finally retired(!) and am making up for lost time. I'm trying to repair two of my old SAs, an Anritsu and an HP; I'm working on the first one, but I'm having a hard time with the second one, partly because I can't find the wiring diagram.i have seen a simimilar post "https://www.eevblog.com/forum/repair/help-needed-to-repair-hp-spectrum-analyser/" but it didn't help me.The SA is an HP 8593A and the screen suddenly became dimmer than usual. I checked the voltages and the -15 was almost absent but trying in stand alone the power supply I found no problems. I did however replace all the capacitors. By disconnecting the various boards, the voltage returned when I disconnected the attenuator, the one with the relays, to be clear. After that the screen returned to brightness but the trace moves jerkily and when injecting a signal that skips the attenuator I don't see it.I see background noise for two seconds, pause for one, and then another two seconds of trace.However, if I unplug the A7 board, the trace is uniform and the SA responds instantly to all keys. I'd think it was an interrupt, but without a schematic, I don't know where to start.Can anyone help me?

author: m k
author_rank: Super Contributor
timestamp: July 29, 2025, 07:15:55 pm
content: 8590 CLIP is available.It has many A7 schematics and -15V is regularly needed.

author: maxniz
author_rank: Contributor
timestamp: August 04, 2025, 01:25:26 pm
content: Hi, I'm back from vacation thanks for the answer .... can you tell me where i can download the schematic ?? i also loojing for that for the attenuator...thanks!!

author: m k
author_rank: Super Contributor
timestamp: August 05, 2025, 01:04:51 pm
content: xDevsScribdKO4BBElektroTanyaSize is ~17M and ~339 pages.
HP8593A spectrum analyzer firmware / ROMs needed - Page 1
Forum section: electronics / repair

author: kazubek
author_rank: Newbie
timestamp: January 29, 2022, 02:27:37 pm
content: Hi,I have an HP 8593A SA with a failed U23 ROM chip. This SA has four 27C512 ROMs... . Anyone has got a dump of these ROMs ?My FW daycode was 90-01-03 and PN of the failed U23 chip is 08592-80077.Thanks for help !

author: ESTechnical
author_rank: Contributor
timestamp: January 29, 2022, 02:46:43 pm
content: Hi,Tryhttp://ftb.ko4bb.com/getsimple/index.php?id=manualsI found this there:http://ftb.ko4bb.com/getsimple/index.php?id=download&file=HP_Agilent/HP_8591_8593_8594_8595_Performance_Spectrum_Analyzer/Agilent_8593A_Set_of_ROMS_1M_new_MB_EPROM_08592-80083848.zip

author: kazubek
author_rank: Newbie
timestamp: January 29, 2022, 03:13:52 pm
content: Thanks for Your reply !Unfortunately these ROMs are not for my processor board. These are for the new version and are 1M. My ROMs are 512k the SA does not boot with the newer FW installed .... Still looking for 8593A 512k ROM dump

author: inlinebeginner
author_rank: Contributor
timestamp: November 03, 2023, 02:38:24 pm
content: I just saved my HP8593A EPROMs, 4 chips, each one is a 27C512 (64K Bytes).See attached file.

author: ps
author_rank: Regular Contributor
timestamp: November 10, 2023, 01:41:54 pm
content: For the later firmwares using 1 Mbit EPROMs you need a different decoder PAL. Replace 08590-80094 with 08590-80159.A zip file with the JEDEC file can be found in this thread:https://www.mikrocontroller.net/topic/404954. You will need someone who is able to burn a 22V10 type PAL or GAL with 25 ns or faster.
HP8594E cal log and linear amp problem - Page 1
Forum section: electronics / repair

author: higgx
author_rank: Newbie
timestamp: August 31, 2022, 09:55:13 pm
content: Hello everybody. I'm calibrating my hp8594e. According to the service manual 2-7 an IF test board(Injector board)(P/N 5062-6421) is Required."A 21.4 MHz signal is injected into an IF test board that has been inserted in place of the first resolution bandwidth assembly, A11. The gain of the A14 log amplifier assembly is adjusted by observing the voltage at the AUX VIDEO OUT on the rear panel with a digital multimeter."The problem is that I can't find any place to buy this board.Does anyone know how to cal a14 without using IF test board ?thanks！！
HP8594E: CAL not possible because reading is 100MHz off! - Page 1
Forum section: electronics / repair

author: Bicurico
author_rank: Super Contributor
timestamp: December 08, 2020, 07:02:35 pm
content: Hi,My HP8594E (one of three) is out of CAL, but I cannot run the CAL routine, because it does not find the 300MHz signal. This signal is currently at around 200MHz!The problem lies within the motherboard, as I have swapped virtually all other components and the problem remains.I hope it is just like a capacitor that went bad, but that is wishful dreaming.The spectrum itself is rendered correctly, I can see the same spectrum as on the other working unit. It is just the frequency reading that is wrong. The AMPL calibration needs to be run, too, but thats another story,Any advise would be welcome.Thanks,Vitor

author: Bicurico
author_rank: Super Contributor
timestamp: December 08, 2020, 07:05:36 pm
content: I do get "ADC-GND FAIL", too.

author: MarkL
author_rank: Unknown
timestamp: December 10, 2020, 03:18:01 pm
content: I don't know what relation the frequency error would have to the ADC-GND FAIL, but I think you could start by digging into why you have that error.There are several pages in the Assembly Level Repair manual on troubleshooting that specific error, including some power supply tolerance checks. Page 615:http://www.keysight.com/upload/cmc_upload/All/08590-90316.pdf
HP8595E YIG Hot-To-Trot 5086-7903 - Page 1
Forum section: electronics / repair

author: wa4whl
author_rank: Newbie
timestamp: May 18, 2024, 06:43:29 pm
content: Hi Fellow HP analyzer owners. I have an interesting problem that has me stumped and maybe someone has seen the same problem and come up with an answer. I am the proud owner of an old HP8595E SA that has worked fine for many years but recently it has been giving me the old refusing to start due to low/no YIG out signal. Opened up the oscillator to have a look and could see no obvious loose gold wire bonds, burned or cracked tracks and the top circuit board tests fine. Finally gave up hoping that it wasn't the notorious bad rf transistor and put it into storage (the attic carefully wrapped) and ready for wherever SAs with dead YIGs go. Hoping maybe some genius will design a cheap YIG replacement (hope springs eternal ;-) )Got bored on a hot rainy afternoon and decided to see if I might decide to part-it-out on ebay given the rest of the unit (ex-YIG) had worked when signal present. Before digging into the unit I thought I'd plug it in and see if power supply still good. Low and behold it the unit started right up like nothing ever was wrong and continued to operate normally for the rest of the day. I powered it off at the end of day normally and assumed the unit had somehow undergone a miraculous " self repair ". Following day I started it up and yes same old death following the initial self checks. I put back in the hot attic and left it for a while, brought it back to the lab and yes it started right up. No problem. So a little testing over next couple hours and a good temperature sensor and the unit has a reproducible pattern:Unit can't get past initial boot tests as long as unit temperature is 81 degrees F or less.Unit boots right up if I put the unit into a room at 83 degrees or higher (after equilibrium) and continued to function normally even at "normal" room temperature until I shut down. Won't come on even if I immediately restart it following a day of operation during which the fan keeps the unit operating normally at a cool 73 degrees.Before I open up the YIG oscillator and start poking around on what appears to be an otherwise clean unit I thought I'd see if anyone has run across this temperature dependence and can suggest a way to focus on the potential source of the problem? That unit is so d#@* sensitive and small to work on. The yig sphere? The obsolete transistor? The silver bonds?Any ideas would be appreciated. WA4WHL
HP8596E no signal in input - Page 1
Forum section: electronics / repair

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 12, 2021, 09:01:46 am
content: P8596E no input signal, only atocal level is performed correctly. By passing the attenuator entering the first converter with a few millivolts 300 MHz, the autocal continues to reply no signal, I ask what exact value in mV it must have at the input to perform the autocal in frequency, in case the problem lies in the first converter module , do I have any chance of being able to locate the fault? Do I have big problems getting into the circuit of the first converter?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 14, 2021, 10:55:44 pm
content: I have not worked on this unit, but since no one else has replied, I will take a guess.The boards in the aluminum cases are surface mount and the first board probably contains a preamp and a mixer followed by another amp.I would think that the sensing circuitry for the input signal is not directly from the input but from the IF signal somewhere close to the first mixer, on the IF freq. I really do not know this unit however.The input signal is mixed there with the Local Oscillator frequency and makes the IF for further processing.If you open it up you can check the various components. The covers come off with multiple screws. If there are discrete transistors (not MMICs) involved check with a multimeterYou can check if you have a Local Oscillator (LO) frequency present at the mixer. You can check if you have the test frequency there also.You can also check if the test frequency goes through the attenuator.Perhaps join Groups.io and try this group, maybe someone there has experience with this particular unit.https://groups.io/g/HP-Agilent-Keysight-equipment/messagesWally

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 17, 2021, 06:30:49 am
content: thank you for your suggestion
HP8753B "Caution: No IF Found Check R Input Level" - Page 1
Forum section: electronics / repair

author: BalticLab
author_rank: Regular Contributor
timestamp: July 18, 2023, 11:07:37 am
content: Hey everyone,hope somebody can give me some helpful pointers to repairing a HP8753B network analyser.On start-up, the frequency range from ~1.5 GHz to 3 GHz works just fine. In the lower range up to 1.5 GHz, the device displays a "Caution: No IF Found Check R Input Level" error message. If I set the start frequency to around 1.6 GHz and the stop frequency to 3 GHz, the message disappears and the measurements appear to be correct. After a short warm-up period, the same error message is displayed in the 1.5 to 3 GHz range. However, there's a small range around 1.7 GHz +- around 100 MHz where the VNA works fine.I have checked all supply rails on the main power regulator card. All self-checks yield a "PASS" result. If I connect the RF OUT connector to an external spectrum analyzer, and set the HP8753B to a CW frequency around 1.6 GHz, a 1.6 GHz signal is clearly visible. However, the displayed level is around -30 dBm with a power level on the 8753B set to 0 dBm. In the range where the "Caution: No IF Found Check R Input Level" message occurs, no output signal can be detected.Before I pull the source assembly out of the device and check the outputs of the two oscillators with an external spectrum analyzer individually, I was curious to hear if anyone has experienced the described behaviour before and could give me some pointers. Also, while I do have the entire service manual, there seems to be no documentation on the source assembly in the service manual. There are quite a few test pins. For instance, there are two pins, 10- and 10+ (could also be ID+ and ID-), which both carry a constant 14.7 Volts. Given the + and minus, this seems a bit suspect.On a side note: I saved the data from all 4 EPROMS on the main CPU card. So if anyone needs the hex files, let me know.

author: Maurizio1957
author_rank: Contributor
timestamp: July 18, 2023, 03:09:19 pm
content: Hi, I repaired my old 8753C in this way:https://www.simonsdialogs.com/2020/04/hp-8753c-network-analyzer-a-new-old-yto-and-a-new-old-firmware/with the help of mr. Simons!73, Maurizio IU5BEC

author: khach
author_rank: Contributor
timestamp: July 18, 2023, 03:41:17 pm
content: Try to reduce output power settings to -5 or -10dbm. At my partially damaged 8753 that settings INCREASE output power to desired level and device working properly except 2-th harmonic generator at 85047 test set.

author: Bud
author_rank: Super Contributor
timestamp: July 18, 2023, 04:51:58 pm
content: Dr Joel Dansmore, the designer of the 8753, frequents the "RF and Microwave" board of the forum. You can move your topic there to help grab his attention.
HP8753D to E conversion - Page 1
Forum section: electronics / repair

author: sixtimesseven
author_rank: Frequent Contributor
timestamp: December 20, 2019, 11:19:27 am
content: HiI was looking into how to convert a HP8753D to an E Version via CPU upgrade.There are new boards available HP parts: 08753-60272However, I did not find any information on how to setup the board and transfer the cal data to the new board. There are commercial services but they charge lots of $$$

author: DarkHelmet
author_rank: Newbie
timestamp: July 07, 2021, 07:18:24 pm
content: sorry for the bump, but did you manage to solve this? I have the same issue.

author: sixtimesseven
author_rank: Frequent Contributor
timestamp: July 07, 2021, 08:41:57 pm
content: Quote from: DarkHelmet on July 07, 2021, 07:18:24 pmUnfortunatly no... In the end i found it to much hassle and cost to upgrade.
HP8753E repair - Page 1
Forum section: electronics / repair

author: bat
author_rank: Regular Contributor
timestamp: January 21, 2025, 01:22:53 pm
content: Hi everybody,I rescued an 8753E a while ago, but I have no clue what happened to it. All I know is that there's a lot of oxidation and traces of salt !!The only bit of info I could get is that this particular 8753E was situated in Casablanca, Morocco, and it was brought back to France in the 2010s.I disassembled the whole analyzer. I am stuck at the moment on the PSU; I wasn't able to find a service manual with the pinout of the power supply. It appears clean, but I believe I am missing something when trying to test it.For the time being, I can't reassemble the analyzer.I will post pictures for the curious later.

author: m k
author_rank: Super Contributor
timestamp: January 24, 2025, 05:58:45 pm
content: If there is a fan, maybe it made the machine sucking sea winds.Still, don't taste the stuff.Can you find any popped capacitors?
HP8753E VNA repair - Page 1
Forum section: electronics / repair

author: cyma
author_rank: Newbie
timestamp: August 26, 2022, 10:07:35 pm
content: I have an HP 8753E that I’m trying to fix.I noted that I was getting a very poor response from port B prior to calibration. Upon disassembly I determined that there had been ESD damage to the coupler and the ~265 ohm film resistor inside was fried. I replaced this with a 270 ohm resistor using instruction I found online. After the replacement, the performance improved somewhat but it is still problematic.I tried swapping the port couplers and the samplers, but regardless of the changes the problem stays on port B. My next suspicion is the solid state switch (A24 - HP 5086-7539).Is there any way to easily test this? Is it possible and/or likely that ESD damage coming into port B would also knock out the switch behind it (which evidently is static sensitive)? Is there any way to repair the guts of this switch or is this a lost cause? Thanks for any insight you can provide.Images:Port B before fixing resistorPort B after fixing resistorPort B with a different (probably good) port couplerPort A (working fine for reference).

author: KE5FX
author_rank: Super Contributor
timestamp: August 26, 2022, 10:14:03 pm
content: The repetitive nature of the artifact is interesting. Its period is long enough to suggest that the fault is not actually at the coupler, maybe as much as a foot or so away. Do you have the time-domain option? If so, switch to that and see what it tells you.

author: cyma
author_rank: Newbie
timestamp: August 27, 2022, 01:08:25 am
content: I did a lot of probing removing various cables along the line and came to the conclusion that the frequency of this only changed when I played with the cable between the coupler and the switch. This seems to be an artifact of the switch coupling to the coupler. I have tried 3 couplers and I know that's not the issue, so I'm leaning more and more towards the switch as the cause of the issue.

author: cyma
author_rank: Newbie
timestamp: August 29, 2022, 11:27:30 am
content: Additional analysis showed that it was indeed the switch that was bad. The problem and solution is well described herehttps://www.mattmillman.com/agilent-8753es-repair-part-2/#comment-103920. I will include a few photos of my repair below for anyone interested. Bottom line: ESD damage on port B . This was clear by connecting port 1 to port 2 and then measuring S21 and S12. One was fine and the other was more than 10 dB off. So I took apart the switch and noted ESD damage to a diode near the input. I tested the DC resistance between the switch inputs and ground and also noted that on the good side it was about 3.6 ohms and on the bad side it was about 1 ohm. I removed the diode (that was shorted) and the switch started working normally again. These diodes are kind of microscopic, so I used a microscope during the process. Ideally, I'd like to replace that diode with a similar one. If anyone knows what diode was used there or the specifications, I'd really appreciate some insight.
HP8921A service monitor high stability reference noisy(fixed) - Page 1
Forum section: electronics / repair

author: TheSteve
author_rank: Unknown
timestamp: September 12, 2015, 09:50:28 pm
content: I recently traded some gear for an HP8921A service monitor. It had a problem which I narrowed down to the high stability reference board. I ordered a replacement board and that fixed the problem. The 8921A now works great. However that still leaves me wanting to fix the original board. HP has never released schematicsfor the 8920/8921 series of service monitors which is a shame. They have released board level repair information only.Enough information was provided to power up the board on the bench. It has a TCXO running at 10 MHz with a 1 GHz VCO that is phase locked and also divided by two to output a phase locked 500 MHz. The main problem is that the 1 GHz output is noisy, the 500 MHz is also less then perfect but doesn't look as bad after going through its divide by two circuitry. I have gone through the amplifier stages and everything seems to look good. It outputs the proper levels. The power supply to the oscillator itself looks good as does the control voltage. I can see it changing to adjust frequency and it looks pretty clean with no noise on it. The main VCO transistor is an MRF581. I have output scans from both the good and bad modules - you can see the noise on the bad one and a slight variation in its output frequency. The various traces are min/max/average and instant.I have also included a pic of the board. It is pretty easy to see the flow of RF through the left hand side of the board starting at the top.I have checked all resistors, power supplies etc, all look fine. If anyone has any thoughts let me know. I already swapped the MRF581 as I happened to have one and it made no difference.

author: TheSteve
author_rank: Unknown
timestamp: September 13, 2015, 05:03:54 am
content: Just a quick update.I identified the bad part. It is U21, an MMIC amplifier. Marked A06 it is an Avago MSA-0686. It still seems to amplify but its input appears to no longer be 50 ohms which causes the VCO to be unstable.

author: py5lf
author_rank: Newbie
timestamp: November 20, 2022, 07:01:32 pm
content: Dear SteveDo you have the schematic for HP8921A ? Mine are showing an alarm RF INPUT OVERPOWER and I want to fix it.Thank you in advance

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 20, 2022, 11:48:53 pm
content: This group has a CLIP with lots of infoHere is the files addresshttps://groups.io/g/HP8924-Family-Spectrum-Analyzers/files/HP-8920A%20and%20HP8920B%20related/8920%20CLIP.pdfI don't know if you have to join to read this, but its free and easy.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 20, 2022, 11:53:18 pm
content: Steve:I had a problem with another MMIC in a HP 8713 VNA. Just stuck in another MMIC that I had with the correct Freq specs and all is good.I think it was the same MMIC (A06), in a different functional location,of course.Wally
HP_8904A partial battery failure - Page 1
Forum section: electronics / repair

author: gmac34
author_rank: Regular Contributor
timestamp: January 16, 2023, 05:52:09 pm
content: Hi, I have replaced the ram battery in a HP 8904A synthesiser, I have followed the instructions on the SM to keep the ram powered while replacing the battery but it seems something has gone slightly wrong. The unit booted and gave me a brief warning about some corrupted ram sectors, and that ram might be defective or battery low, I didn't manage to take a picture of it. The unit now seems to work fine, and still shows the right serial and options, the error doesn't show up on subsequent boots, did it fix itself? should I bother doing anything?Thanks

author: coppercone2
author_rank: Super Contributor
timestamp: January 17, 2023, 12:11:04 am
content: crap I just took mine apart after reading this, looks like I got some lithode bull shit going on. Need to replace with a different cell, it might be ready to goI looked at this a few years back and decided I would fix it and I forgot about it.Going to put one of these bad boys in its placehttps://www.digikey.com/en/products/detail/panasonic-bsg/BR-2-3AT2SPN/31750Looks like it needs a mechanical adapter of some kind, made of silicone paste most likely.set condition red on the ship!

author: coppercone2
author_rank: Super Contributor
timestamp: January 17, 2023, 12:50:02 am
content: and I think I had errors on that when I bought it for some reason, they went away but all functions work.I recommend you hook it up to a scope and try the diff functions and see if there is a problem.

author: gmac34
author_rank: Regular Contributor
timestamp: January 17, 2023, 01:19:07 am
content: that should be the right battery but it would be easier to get one with 3 pins like this onehttps://www.batteriesdirect.com/product/details/specialty-batteries/panasonic/br2-3ae2spnthat should be a direct replacement, at least for the models with serial prefix 2942A and above, I'm not sure what is best to use in the early version. It's also a pain to get those in Europe because you cannot ship them by air...I still had the original one in, marked 1991, still measuring 3.1v.. the don't make them as they use to... but how could I trust a 30 Y old battery? It did it's jobI tried a few things and all seems normal, not sure what is on the RAM apart form the serial and options, and perhaps some saved settings, the rest of the important stuff is in the ROM.There is anyway a way to recover form a battery brownout, but I did not see any mention about a partial, recoverable? corruption.

author: coppercone2
author_rank: Super Contributor
timestamp: January 17, 2023, 02:17:35 am
content: oh no I have one that looks like a disk that is stainless steel welded. That is the newer one, but the battery voltage is correct, so I just need to make an adapter. I though that one would be easier to inteface with wires since certainly it will be glued upright with silicone and some extra wires.
HP/Agilent 33120A - both broken cables for BNC output  - Page 1
Forum section: electronics / repair

author: flair4ever
author_rank: Newbie
timestamp: January 25, 2020, 05:27:21 am
content: hello, allI am pretty new to repair and I got a Agilent (same as HP) 33120A from junk yard.When I opened it, the output cable and BNC cable were both broken.I powered it up, and probed at the open-ended output cable and found that it is working just fine. Lucky me!Now, my problem is how to repair the BNC cable inside the unit. Please refer to the pictures as attached.Do you guys have any ideas??Thanks a lot!!Zhao

author: mr.fabe
author_rank: Regular Contributor
timestamp: January 25, 2020, 09:13:19 pm
content: Potential remedies in order of cost...You can try and trim the cable, insert the cable back into the BNC jack and solder the cable outer shield to the BNC ground but it may not be a reliable connection for the center clip.You can replace the BNC jack, trim the cable, solder the center and ground to the new panel jack. The original BNC jack may be tough to remove.You can look for replacement cables or a panel with front jacks installed.

author: flair4ever
author_rank: Newbie
timestamp: January 26, 2020, 04:55:46 am
content: Thank you very much for the detailed suggestions!!I was lucky yesterday to carefully put it back to BNC connectors, and kapton taped it around the inner side of the case.Now it works just fine!!Thanks again

author: HighVoltage
author_rank: Super Contributor
timestamp: January 26, 2020, 11:03:45 am
content: You are lucky, that was an easy fix.Usually these coax cables are crimped on to the front connector and it seems the crimp tubes are still on the cable. I would try to crimp them on again or may be just push them on for good ground connection.

author: humgar
author_rank: Regular Contributor
timestamp: July 15, 2022, 06:41:52 am
content: I also had a beat up BNC port for my 33120A. I wonder how was the BNC port secured to the plastic case in the first place as I don't see any screw/nut there. Do you know any compatible BNC header/socket that'd fit the plastic panel? Thanks in advance.