53132A TB CAL FAIL - Page 1
Forum section: electronics / testgear

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 06:44:11 pm
content: Anyone know what in particular causes this error? Is it the timebase itself, the incoming signal, or something else? "Fail" doesn't mean a whole lot to me. Per the manual:"TB CAL FAIL You have invoked the TIMEBAS? choice from the Calibration menu item CAL:, and the calibration failed."The manual claims it should not fail if the 53132A has been heated up/on for 24 hours. I've had it plugged in for over a month now (the PS+oscillator heater are always on if the unit is plugged in). I tried leaving the counter actually on (display on) for several hours, and yield the same issue (don't think this helps, as the counter is already hot from being powered all the time).Some background:A few months ago I bought a new-old-stock 53132A, and then upgraded it with a clone high-stability timebase and 3ghz prescaler from eBay (shipped from Poland, same as the one reviewed by Shahriar).I'm feeding in the 10Mhz sine output from my BG7TBL (2014) unit. The BG7TBL is locked but has only been running for about 12 hours. The output "looks" stable on my other counter.The cal runs for a while, and then results in "TB CAL FAILED".I was able to successfully calibrate the unit a month or so ago with FEI rubidium oscillator, but now I get the same error with that. Also tried feeding the OCXO output from my Philips counter, get the same error.I'm wondering if maybe the used OCXO that came with the high-stability timebase from Poland has failed in some fashion?

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 08:40:41 pm
content: I should add that the clone high-stability OCXO seems to have drifted about 12Hz in the past two months. This makes me think that the OCXO is dead/dying and can't be trimmed back into spec.The Morion OCXO I received did look quite torn up/old. I contacted the eBay seller, but would still like to know if anyone has had a similar experience.Thanks in advance.

author: motocoder
author_rank: Unknown
timestamp: August 26, 2015, 08:47:18 pm
content: Quote from: dadler on August 26, 2015, 08:40:41 pmCheck for a missing shorting jumper on your OCXO. The one commonly sold on eBay comes in two configurations. One just has a trimpot and does not have the D/A circuitry populated. The other has the D/A circuitry for auto-cal, but does not have the trimpot. There's a jumper that needs to be installed to enable the D/A functionality, and for some reason putting that jumper on there seems to be beyond the technical capabilities or care of the eBay seller.I bought one of these OCXO for my 53131A off of eBay. I had the same problem. I hooked up the frequency reference to channel 1/trigger on my scope, and the counter 10 MHz out to channel 2, and ran a timebase calibration cycle. It was immediately apparent that the oscillator was not having its frequency adjusted at all. I checked, saw the missing jumper, put one on and re-ran the cal - problem solved.

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 09:03:29 pm
content: Ah thanks so much for the response!Here's what my board looked like before I put it in:

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 09:08:16 pm
content: Now that I actually look at the circuit, seems that trace in the center of pic #4 is going off into the ether... Guess that's the trim pot and buffer? I'm not familiar with the pinouts on these oscillators. Can't tell what's under the OCXO/DAC exactly although I can sort of make it out.Is the jumper your referring to the one in pic #6?I was able to calibrate this OCXO once, just after I received it. Don't know if it was actually adjusting anything, but on first try I got TB CAL PASS and it was nearly in-spec compared to my other counter.

author: bson
author_rank: Unknown
timestamp: August 26, 2015, 09:50:18 pm
content: Quote from: dadler on August 26, 2015, 08:40:41 pmThis is likely the problem - not that it's dying, but that it has drifted too much to be tuned to spec, or to be calibrated.However, doesn't this particular OCXO have a trimmer for a rough frequency adjustment? Of course, the presence of a trim pot is a problem since the pot is likely to be the least stable piece, so adding a pot means you'll have to regularly adjust it.

author: motocoder
author_rank: Unknown
timestamp: August 26, 2015, 10:00:47 pm
content: Quote from: bson on August 26, 2015, 09:50:18 pmAgreed - 12 Hz is awful. The Morion OCXO are very good if they don't fail, but I have read they have a high failure rate in the first 30 days. You may just have a bad one. But we should first establish if the frequency trimming is working at all.dadler - that is a totally different board than the one I installed. To establish whether its frequency adjustment is even working at all, can you do what I did and connect the input ref and 10MHz output (from the back of the counter) to your scope and see what happens during cal? You should see two waveforms, one of which appears to be moving forwards or backwards relative to the other one. During call, the speed of movement should change (if it was working, it would slow and eventually come to an almost complete stop). This will tell you whether the instrument is able to adjust the OCXO at all.If it's not too late, I would also make an attempt to contact the seller. If you haven't left and can still leave feedback, that's usually an effective tool to get them to respond. I can also provide a link to the OCXO board that I bought, which I know works well.

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 10:10:27 pm
content: Quote from: motocoder on August 26, 2015, 10:00:47 pmThe fact that I was able to calibrate it once, and it matched my old-school Philips counter w/ OCXO within 1Hz, makes be suspect the OCXO (they now differ by 12Hz, and the Philips matches my two GPSDOs and the Rubidium unit, for the most part).I purchased this board from this seller:http://www.ebay.com/itm/Ultra-High-stability-Timebase-for-HP-Agilent-53131A-53132A-53181A-Counters-/111678771404?ssPageName=ADME:X:AAQ:US:1123I believe this is the same seller than Dave/Shahriar purchased their clone upgrades from.I contacted the seller and told him of the issue, waiting on a response.I bought this oscillator back at the beginning June, so I already left feedback as it worked and calibrated. Probably should have waited, but in my experience, if I wait a super-duper long time to leave feedback, I seldom get feedback left for me in return.I will perform the procedure you have mentioned and try to see if the DAC is actually changing the output of the oscillator at all.I'm also thinking of picking up a less-ratty-looking Morion MV89A on eBay, just as another device to test with.Thanks again for all of your responses.

author: motocoder
author_rank: Unknown
timestamp: August 26, 2015, 10:15:36 pm
content: Quote from: dadler on August 26, 2015, 10:10:27 pmI updated my previous post. I didn't realize it was 12 Hz - and bson is right that this is likely the issue. I have read that these Morion units have a high failure rate in the first 30 days, but if you make it past that they are pretty good. So could be your OCXO has just gone Tango Uniform.This is the one I bought:http://www.ebay.com/itm/181759655189?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITI want to compare the photos and see if they are actually different. I didn't recall the board being that small, but it does look more similar to yours than I thought initially.

author: dadler
author_rank: Unknown
timestamp: August 26, 2015, 11:32:46 pm
content: Thanks.Do you guys know if there are lots of different versions of these MV89A oscillators?Mine came with one labeled MV89A XO00281M-CT-MV89I see some on eBay with this labeling, but usually no production year.There are some newer ones that are labeled e.g. "XO00281M Rev.3 30062000011", but I don't know if these are the same class or not.None of the numbering seems to match the datasheets I have found:http://www.morion.com.ru/catalog_pdf/MV89-OCXO.pdf

author: motocoder
author_rank: Unknown
timestamp: August 27, 2015, 12:04:42 am
content: Quote from: dadler on August 26, 2015, 11:32:46 pmI don't know, although I haven't heard of there being versions of the MV89 with significant differences for the MV89. The only thing regarding class that's mentioned on the data sheet is the "A" suffix, which just specifies a temperature grade, not any difference in other specs. I think they go for about $25 - $30 on eBay, so that might be a cheap fix if you can determine conclusively that it's the OCXO that is the issue.BTW, I confirmed the board in the pics you posted is definitely different than the one I bought. Yours does not even have the jumper that I mentioned, so jumper having fallen off is not the issue.

author: dadler
author_rank: Unknown
timestamp: August 27, 2015, 07:00:55 am
content: I see-thanks for the info.The seller responded and says he offers a 12 month warranty. I am sending the timebase back to Poland for repair. I guess I'll be back on the old Agilent tweak-a-pot crystal for a while. The factory oscillator in these units is terrible.

author: motocoder
author_rank: Unknown
timestamp: August 27, 2015, 07:20:56 am
content: Quote from: dadler on August 27, 2015, 07:00:55 amYeah, it's pretty bad. Glad to hear the seller stands behind his product. You could also grab a GPSDO and set it up as an external reference. There's a couple of recent threads on this topic:https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/https://www.eevblog.com/forum/testgear/economical-option-for-precision-frequency-reference/

author: dadler
author_rank: Unknown
timestamp: October 28, 2015, 07:30:54 am
content: Just an update: I returned the timebase to Poland, and the seller sent me a replacement (which calibrated correctly).Turns out the OCXO itself was working--It seems the DAC failed. Generating negative voltage regardless of input.I don't know what would cause a DAC to fail spontaneously.

author: Orange
author_rank: Frequent Contributor
timestamp: October 28, 2015, 07:44:33 am
content: Quote from: dadler on October 28, 2015, 07:30:54 amMost likely ESD (Electrostatic Discharge) during manufacture. These failures can sometimes manifest themselves after a while....

author: BarsMonster
author_rank: Contributor
timestamp: October 24, 2022, 09:05:07 pm
content: For future generations: I've verified calibration range for 53132A 010 timebase option. It can adjust OCXO in approximately +-3.5Hz range.If it drifts beyond that range - that's the root cause of the issue for this error message for original OCXO.