HP8594E calibration question. - Page 1
Forum section: electronics / testgear

author: stigwurx
author_rank: Contributor
timestamp: September 08, 2019, 02:31:29 am
content: Hi all,I'm in the process of rejuvenating a HP8594E that was rescued from a dumpster , the poor mite. First issue was a failure to boot , blank screen and only a splash of vertical lines when I hit the preset button. Pullled the GPIB interface card and it came back to life , that's another days work but in the meantime I decided to see what she could do.Ran the self calibrate frequency and amplitude which returned CAL: RES BW AMPL FAIL .Went to the manual which suggested either a hardware failure needed addressing or a calibration issue . So I went the recalibrate route for starters, that's chapter 2 section 5:Crystal and LC Bandwidth Filter adjustment in the "8590 Series Analyzers Assembly-Level Repair" service guide.Made the crystal shorts as specified and followed the instructions , went along until I got to the section on LC centering. The following is the part of interest25.Short A11TP10 and A11TP11, A11TP12 and A11TP13, andA13TP10 and A13TP11 using the crystal shorts used in the crystalalignment section. Press the following analyzer keys.BW, 30, kHzSPAN, 200, kHzMKR FCTN, MK TRACK ON OFF (OFF)BW, 100, kHz26.Adjust A13C45 LC CTR for maximum signal at center-screen.27.Move the short from A11TP10 and A11TP11 to A11TP12 andA11TP13, then adjust A11C23 LC CTR for maximum signal atcenter-screen.28.Move the short from A13TP12 and A13TP13 to A11TP10 andA11TP11, then adjust A13C45 LC CTR for maximum signal atcenter-screen.29.Move the short from A13TP10 and A13TP11 to A13TP12 andA13TP13, then adjust A13C23 LC CTR for maximum signal atcenter-screen.30.Disconnect all the shorts from A11 and A13 bandwidth boardassemblies.As soon as I got to step 27 I went , huh ? So I guessed A13TP12 and A13TP13 were to be shorted given the adjustment that was to be made. I just followed the remaining steps as written but suspect they might be ass too.I finished the procedure with Marker delta frequency of 4.5kHz , so that's within spec. Went through the Final BW Amplitude Check , passed self cal amp and freq , the CAL DATA correction numbers were within the margins specified. All looks to be fine ... but is it ?So to cut a long story short, has anyone got a corrected version of this part of the manual or is it actually correct and I'm just missing the point. Has anyone else out there done this procedure successfully ?Any suggestions gratefully received.Regards to all.

author: ps
author_rank: Regular Contributor
timestamp: September 15, 2019, 10:59:28 am
content: There are four filter stages, and you are calibrating one after another. So you are shorting out three of them while adjusting the fourth one.In step 27 it should read A13... instead of A11... You always adjust at the position where no short is.

author: Bicurico
author_rank: Super Contributor
timestamp: February 11, 2020, 10:14:31 pm
content: Hello,One of my HP 8594E is behaving strange...I turned it on today just to check on it and it gives a LOCK OFF error and asks me to perform a calibration.First it did not work, because the 300MHz signal was more than 50MHz off. After I connected a signal source that showed a signal where the SA thought 300MHz was, I managed to get it to calibrate itself to a point where it started to run the calibration on the CAL OUT port again.So far so good.But now I am seeing the "CAL: RES BW AMPL FAIL".I read the service manual (chapter 2 - 5 Crystal and LC Bandwidth Filter), but I have some questions, since I never did anything like this and the manual lacks pictures...1 ) With the cover removed, I can see the A14 and A9 boards, but there are no labels on the remaining boards! I assume they are (in this order): A14 - A13 - A12 - A11 - A9. Can someone confirm? Why is ther no A10?2 ) A13 and A11, which are to be configured during calibration use the same board, correct? They look exactly the same to me.3 ) I don't have any "crystal shorts", but from looking at the boards the pins look like I can just use regular computer jumpers. However, I am afraid I might drop them by accident inside the board cases. I imagine that the HP crystal shorts have some long extensions that makes inserting and removing them easier. I could glue some strips on the regular jumpers... Am I correct to assume that this is what those crystal shorts are all about?4 ) The manual warns to not ground the pins by accident. That can easily happen since the casing is GND. Any tips on how to avoid an accident? I considered removing the cover of A13 and A11, so that inserting and removing the jumper is easier.5 ) The manual says " adjust A13C17 LC dip for a minimum signal amplitude": Am I correct to assume that the minimum amplitude is indeed a minimum as in: if i turn the dip's too much to the left or right, the amplitude will increase in both cases and I need to adjust the dip (plastic screw) to get the minimum amplitude?6 ) CAN I INSERT/REMOVE the jumpers with the SA switched on?7 ) When it gets to LC Alignment, the manual says: "19.Widen all but one of the LC filter poles by shorting A11TP10 and A11TP11, A11TP12 and A11TP13, and A13TP10 and A13TP11 using the crystal shorts.": what do they mean with "Widen"8 ) Do I have to do the LC alignment/centering in any case or should I try and do only the first part for the Crystal Alignment and then try to run the CAL FREQ/AMP again?Sorry for the lame questions but this is totally new to me without any additional information besides the service manual.Thanks,Vitor

author: Bicurico
author_rank: Super Contributor
timestamp: February 11, 2020, 10:33:49 pm
content: Just found that the Crystal Shorts are NOT plain jumpers:https://www.eevblog.com/forum/repair/hp-8594e-87461/msg1470524/#msg1470524Crystal bandwidth shorts (set of three) 5062-4855 A,TComponents Needed to Build One Crystal Short6a 0.01 µF capacitor 0160-48326b 90.0 Ω resistor 0757-04006c Square, single-connector terminal (two required) 1251-41826d Two-terminal connector body 1251-06896e 3/16 inch dia. heat shrink tubing, 1 1/8 inches long 0890-0029The next page on the service manual shows how to build this.Regards,Vitor

author: Bicurico
author_rank: Super Contributor
timestamp: February 11, 2020, 10:39:54 pm
content: I have another question: having the resistor and capacitor in series, will it matter which way around I insert this crystal short?I guess not, but thought that I better ask anyway...Thanls,Vitor

author: ps
author_rank: Regular Contributor
timestamp: February 26, 2020, 06:49:14 pm
content: a) it does not matter.b) on a PCB you would put the capacitor to the low-impedance side (output), and the resistor to the high-impedance side (input)