7A13 Differential Comparator

[Hoopty]

OK, I'll start this forum off.  I've been wondering if anybody out there is replacing their 7A13 Diff Comps?  If so, with what?  And conversely, if not, what are you substituting?  

Jesse

[browndav]

Well, I wrok at the PMEL lab at Eglin AFB and we have three 7A13 differential comparators.  We also have the 7A22 diferential amplifiers, but thats really a k3/k4 section peice of equipment and you listed this posting in the k1/k8 section.

[Hoopty]

Yeah, I was a little concerned with where to put it...  but I ended up putting it in K1 because we use them mostly for beer cans and 500 testers, which are handled in that section @ Nellis.  The K3 forum would have worked as well too I suppose.

Jesse

[browndav]

I see your point as to where its used but is the forum to be set up for where the equipment is used or where it is CALIBRATED?  Such as EVERY section uses a DMM but Im not sure I'd want to post a question about a 3458A in the K6 area simply because im using it to cal equiptment in that section.  Maybe there should be a note or something stating to post questions about particular peices of equipment within the k-area they are calibrated.

Just a thought.

Thanks.

[Hoopty]

Well, my question dealt with the use (which is pretty much limited to a few items for this plug-in).  If it dealt with the repair and/or cal, I suppose that would have been different.  Ultimately, it's not a big deal.  If I'm coming to the site to look for a 7A13 problem, I'll use the search function, and it'll show me all relevant topics.

[Anonymous]

As the section supervisor of the section that calibrates the 7A13s here at Eglin, we are managing to keep our running at this time.  There are some work arounds for using other items.  But that depends entirely on application.

[MikeyB]

We dont even use the 7A13 anymore for beer cans and other sorts of test sets.  For beer cans, 501s and 500 testers i just use the LeCroy O'Scope.  All you have to do is hook a 5700 up and make sure the offset is right.  From what I remember from F15/16 stuff, the accuracies(sp) of the 7A13 became so bad that you have to hook up a 5700 and transfer standard it anyways.  Correct me if im wrong....

[Mr.Steve]

Jesse

As I recall, I used something like the TDS 420A Tek Scope in lieu of the 7A13, when I worked K1 and beer cans at Kirtland.  Kirtland I think had a TDS 620? not sure?  But any ways, you can use the 3458, but have fun using the hard to find peak function.

Steve

[Targo]

I've been working this issue myself simply because the 7A13's at Kunsan both took a dump last year.  What we came up with therer was to use the Lecroy scope and set up an offset using a DC level from the 5700A().  Worked like a champ!!!

Tried it here at my current base but had an awful lot of noise.  I was able to make the measurements but cant recommend it as a replacement method yet here.

More along the issue that I believe needs to be dealt with.... particularly on the 130 mV pulse amplitude.  I did some research on this one a while back.  If you read the section in the Mailnt TO that tells what this step actually checks.  Then read the calibration section and the K-pro.....  It is my understanding that an "almost" arbitrary pulse of more than 120 mV will suffice to make the test work.  Any input on this?

It seems that everyone have asked, can only think of the beer cans and 500 boxes as the reason they need to keep 7A13's around anymore.  In fact, at Kunsan, we had started making the entire 7000 series CBU after the LeCroy work-around .... there was no other reason to keep the entire series calibrated

[Hoopty]

I had been looking at this item as a possible replacement while I was at Nellis.  It looks like AFMETCAL has done some research and the LeCroy is actually good enough to replace the 7A13.  Below is straight out of the latest newsletter. (The entire document can be found in the download section)

REPLACEMENT FOR THE 7A13 DIFFERENTIAL COMPARATOR



LeCroy Differential amplifier model DA1855A. AFMETCAL has identified a replacement for the 7A13 Differential Comparator. The LeCroy Differential Amplifier model DA1855A has specifications very similar to the 7A13 and was designed by engineers that had previously worked on development of the 7A13.



AFMETCAL was able to borrow a DA1855A and schedule a trip to Wright-Patterson AFB PMEL to run 33K1-4-1506-1. This technical order (TO) supports over 380 Voltage Detectors, Part Number 467-2 (CS9216-2) and 467-3 (CS9216-3), in the Air Force inventory. We were able to run the TO successfully using the LeCroy Differential Amplifier in place of the 7A13 without any problems.



The 7A13 is used in 81 additional calibration procedures. Technical Content Managers will be conducting a review of these TOs and the 7A13 will be removed if you can make a make a direct measurement using an oscilloscope. If the required accuracy is such that a differential comparator is needed, TOs will be modified so that the DA1855 is the primary Differential Amplifier in Section 2, Equipment Requirements and the 7A13 will be listed as a substitute item. This will give PMELs maximum flexibility.



AFMETCAL encourages labs that use the 7A13 heavily to consider procuring the LeCroy DA1855A. The DA1855A is stocked listed and item managed under NSN 6625-01-495-8054, the unit price is $3,495.

[howiesatwork]

We use an Infinium.