HP 8595E stops hard on 2.930GHz - Page 1
Forum section: electronics / repair

author: Astralix
author_rank: Regular Contributor
timestamp: April 01, 2023, 10:17:41 pm
content: Hi!I have a HP8595E 6.5GHZ Analyzer that I used for years. I also added in the missing tracking generator and used that for years. But I only worked far below 1GHz, till today... I tested the unit against an SMIQ 03B and stunningly found that the signal displayed disappears from the analyzers screen as soon as I step over 2920MHz. The SMIQ is working fine, I tested it against an FSEB30.When I look at the screen in full span, I can see a slightly rising graph from 0 to ~3GHz and then it gives a slight notch and the graph is going vertical. So some mixing thing must be bad.I also observed a carrier at around 570kHz that has almost 0dBm that probably shouldn't be there at all.The photo shows the CAL signal fed into the RF input. See the small dent on the graph short of the 3GHz center line?

author: rhb
author_rank: Super Contributor
timestamp: April 02, 2023, 10:51:41 pm
content: I have an 8560A & 8593E. Both have the tracking generator which stops at 2.9GHz. The 8593E will not sweep across the 2.9GHz boundary.I suggest asking on the HPAK groups.io list, but I think it's a design limitation.Reg

author: Astralix
author_rank: Regular Contributor
timestamp: April 03, 2023, 06:09:57 am
content: Hi!The TG only works up to 2.9GHz, that is correct. But the Analyzer still works up to 6.5GHz when not being used in combination with the TG.Astralix

author: shashitej
author_rank: Contributor
timestamp: April 03, 2023, 07:35:07 am
content: Hi,Can u show the pic of the Analyzer, CF set at 3GHz, Span as per conveniencefeeding an 3GHz, 0dbm from working SG.shashi

author: fourierpwn
author_rank: Regular Contributor
timestamp: April 03, 2023, 08:42:14 am
content: Module A3A7 is a 3 to ~ 6.8 GHz YTO, which gets fed into module A3A6, a dual band mixer. Looking at and around these to ensure all signals are present and within spec would be a good start.

author: Astralix
author_rank: Regular Contributor
timestamp: April 03, 2023, 09:25:45 am
content: Hi!Yes, I will check around the 3 to 6GHZ YTO. I already feared that there is a chance that the YTO has died because of it's age. But I'll check all signals around there.Shashi,I set an SMIQ to 3GHz @ 0dBm and I have a -40dBm signal on the screen of the 8595E.Shifting the SMIQ frequency slowly below 2.8GHz and I have to shift the CF a bit up and down, but then the signal is shown as ~2dBm. Moving the CF to 3GHz again, the signal is shown at -40dBm again.Looks like at the moment it hands over to the other YIG, a signal is low.

author: shashitej
author_rank: Contributor
timestamp: April 03, 2023, 11:46:45 am
content: HI,As U & fourierpwn mentioned, the YIG's are to be checkedcheck the input of the RF Switch A3A2 i.e. the outputs of A3A3 LPF & A3A8 YTF ,the output of LPF is ok so no problem.If the output of YTF is ok then RF switch might the problem, if not as u both said YTF or beyond module to be checkedShashi

author: MarkL
author_rank: Unknown
timestamp: April 03, 2023, 01:33:43 pm
content: Before digging into troubleshooting, you might want to try running the FREQ & AMPTD self-cal, and then follow with the CAL YTF.If the YTF pre-selector is not correctly tuned, it can cause amplitude problems on the high band.

author: MarkL
author_rank: Unknown
timestamp: April 03, 2023, 01:47:57 pm
content: Quote from: shashitej on April 03, 2023, 11:46:45 amI think you are looking at the wrong diagram (8593E?). The 8595E has a combined YTF and RF switch module called the SYTF. It unfortunately is a common point of failure.

author: Astralix
author_rank: Regular Contributor
timestamp: April 03, 2023, 03:26:56 pm
content: Hi!Quote from: MarkL on April 03, 2023, 01:33:43 pmI had not used the instrument for over a year, so when pulling it from the storage shelf I let it warm up 30 Minutes and did a full CAL. So unfortunately that will probably not solve the issue.Quote from: MarkL on April 03, 2023, 01:47:57 pmOkay, it is time to pull the diagrams and dig into that myself. I initially posted the request for help as I am running out of time before my vacation. But with all your hints it look like I have to dig into the unit somewhat deeper. But that has to wait two weeks.Thank you all and I keep you updated about the repair.

author: shashitej
author_rank: Contributor
timestamp: April 04, 2023, 09:32:41 am
content: Quote from: Astralix on April 03, 2023, 03:26:56 pmHisorry for the errYeah Astralix update the repairs

author: rhb
author_rank: Super Contributor
timestamp: April 04, 2023, 01:06:26 pm
content: I am fairly certain that what you are observing is a design "feature". I just put my 8593E in storage at another location. I'll bring it home and perform some tests tomorrow.I spent a *lot* of time in your rabbit hole. The upward slope is also present on my 8566B above 2.9 GHz.I strongly recommend reading the manual again. That was how I determined it was not a fault condition.As I remarked before, join the HPAK list and ask there. They are the hardcore HPAK folks. Many of the original design teams follow it. And it's entirely devoted to repairs.Reg

author: Astralix
author_rank: Regular Contributor
timestamp: April 04, 2023, 06:22:04 pm
content: Hi Reg,I already opted in for the HPAG forum as I am already on groups.io helping out myself in R&S repairs. I posted the question and pictures.The repair now has to wait a little time till I am back. But I keep everyone updated.Astralix

author: MarkL
author_rank: Unknown
timestamp: April 05, 2023, 12:56:19 am
content: The 8595E uses two bands to cover its input freqeuncy range. Band 0 is 9kHz to 2.9GHz and Band 1 is 2.75GHz to 6.5GHz, so there is some overlap between the two.Your 2.9GHz test signal falls into both bands, so the analyzer will choose one band or the other for the sweep. The reason you are seeing your signal drop is because some of the sweep settings you've chosen have fallen into Band 1 (the high band) and something is clearly wrong with Band 1. You can force the analyzer to use one band or the other if you'd like to verify this behavior (under the FREQUENCY menu, "Band Lock").Did you perform the YTF CAL, and did it complete successfully?With the symptoms you are describing, there is likely something wrong with the high band conversion or filter. As mentioned before, a common failure is the SYTF module.The easiest way to troubleshoot this, when you get back, is to feed the analyzer the test signals shown on the Assembly Level block diagram (5GHz to test the high band), and check the test points for the indicated signal level and frequency (also on the diagram).The Assembly Level manual also has detailed descriptions of the RF and LO sections shown in the block diagram, which is worth reading.I participate on HPAK too, but I find eevblog much easier to operate.

author: rhb
author_rank: Super Contributor
timestamp: April 05, 2023, 11:37:55 am
content: I agree about EEVblog, but there are some real heavy hitters on the HPAK list. All the many OEM lists on groups.io are a must if you are repairing or diagnosing T&M kit from those makers.MarkL's comment suggests that my 8593E has the "band lock" set. I bought it mostly because it was too good a deal. The 8560A is the one on the bench as my interests are HF and it was already on the shelf when I got the 8593E. The latter was an AT&T cell site kit with the backpack.Reg

author: MarkL
author_rank: Unknown
timestamp: April 05, 2023, 03:57:59 pm
content: The Band Lock persists through a power up if you have POWER ON LAST set. The analyzer will also set the Band Lock to Band 0 (9kHz to 2.9GHz) if the tracking generator is turned on. Even if the tracking generator is turned off, Band Lock 0 will still stay set.Band Lock is automatically turned off (reset to the full range) on PRESET, or you can turn it off manually through the FREQUENCY menu. Your 8593E should be sweeping the full range after PRESET.It's possible that your 8593E could be overriding the default band behavior if it was programmed with ONPWRUP or other event command, but that seems unlikely.I have two 8595E, one of which was diagnosed and repaired that had the exact symptoms the OP is reporting.

author: rhb
author_rank: Super Contributor
timestamp: April 06, 2023, 01:31:25 pm
content: Thanks! That probably explains my experience as I pretty much did the steps you outlined when I powered it up for the first time. Since my 8560A is already on the bench w/ a TG and the 8993E is in its backpack I don'i use the latter often unless I either need the range or take it somewhere.Reg