Stancor A-3898 Data?

[KA8WTK]

All,
  In my quest for a good match between modulator and final, I have been re-evaluating my connections on the A-3898 modulation transformer in my 812 rig. I seem to find two sets of connection data avilable and they don't seem to be the same.
  If you look on "The AM Window" you will find one set of connection data. This is what data can be found with a Google ther and in other places. I have a data sheet (attached) that shows a different set of connection data. To further complicate things, the current listing in the easily found data is lower that what appears on the sheet I have. I know it is not a clear image, so look close.
  Anyone have a guess as to why? Did the transformer ratings or construction change somewhere along the way? It sure is a mystery to me.

Bill

[ae7db]

Bill,

The sheet is hard to read when I download it, but to me it really looks like it is for a 3896 transformer.  The font used and the smudging make it look a bit like a final "8", but to me it looks more like a "6".

May be worth your while looking at with a little magnification.

73,
Dean

[W8VG]

Bill,

I had same problem with A-3894 (125 W version) used in 811A modulator.  I was old beastie I lugged home years ago--got it for a song--appeared very old and and several lugs were broken off, etc.  When I was building modulator and looked at the terminal numbers and layout, noticed they were different from those on the AM window.  Finally after much searching, found older yellowed sheet posted on some forum--was similar to what you have here. 

That particular version had numbering consistent with terminals on my tranny.  After being confused by ohming them out, I decided to use filament tranny and VTVM to check voltages for several connections on primary vs secondary--the older yellowed sheet was correct and had terminals numbered consistent with older model. 

Left me wondering if STANCOR modernized/updated these over years.  To wit, I have since acquired a newer A-3894 with same connection/numbering as what's on AM window.  Appears to be much newer also.  Additionally the original 3894 had both sets of connections on one side whereas newer one has connections on both sides in addition to different numbering for windings and taps.  Interesting!

My original appears very old--like a pre-war or early post-war model.

Hope this helps.  All my stuff is back in my basement in VA unfortunately or I'd post my older copy and some pics. 

73's Geo

[W8VG]

This should point out differences.  Found pics of newer 3894 on web--note how terminal numbering in both these pics is different from what's on your connection diagram?  That was my problem in building modulator.  Suspect windings are same but numbering was changed from older variant to newer model.   So I just used the one that was consistent with my terminal layout/numbering and checked voltages with output of filament tranny and VTVM.  Was a go. 


73's
Geo

[KA2DZT]

I have a 3898.  I think Stancor used two different numbering layouts of the terminals.  I'll have to take another look at it, but I remember when I had the xfmr on the bench that there was something different about the terminal numbering from what other Stancor mod xfmr used.

I'll recheck the 3898 and report back in a few days.

Fred

[KA8WTK]

Thanks for the information so far!
The unit is really an A-3898. The problem with the image I posted is it is a scan of a print out of a TIFF image. I can't post a TIFF so I had to print it and scan as a JPEG and lost a lot of clarity. The TIFF image, enlarged, reads "A-3898" in the upper right corner. Also, the numbering and layout of the posts on the sheet matches.

What may have happened, as Geo indicates, they may have kept the numbering and layout the same but a manufacturing change caused the terminals to be different actual connections inside. As in if post #1 was the end of a winding, it might in later production be a center tap of a winding.

Now that I know the possibility really exits for there to be a different connection scheme, I will ohm it out and see "who" really is "who" in that hunk of iron.

THANKS!

[Steve - K4HX]

Post the image as a PNG or GIF for better resolution.

[KA8WTK]

A better scan of the data sheet.

[KA2DZT]

Can't really see the data sheet that well.

Question,  how are the numbers laid out.  1-2-3 in top row and 4-5-6 in bottom row as same on other side??  Or, is it 1-3-5 in top row and 2-4-6 in bottom row??

Just located my A-3898 (I have 1000+ xfmrs).  My numbering is the 1-3-5 on top row and 2-4-6 on bottom row.  What is strange and not the same as the smaller Stancor mod xfmrs is that each winding is connected to a row of numbers.  1-3-5 is one winding tap being 3, etc.  So, what's different is that each winding is not connected to consecutive numbers.

That's the reason there is a different impedance chart for the A-3898 and A3899.  You can't use the chart that is for the smaller Stancor mod xfmrs.

Hope this helps,

Fred

[KA8WTK]

Hi Fred,
  Mine is wired like yours: 1, 3 and 5 in the top row with 3 being the center tap.
  Like was mentioned in an earlier post, there must be two different "flavors" of the A-3898; perhaps early and late production. So, you need to take care to see which data sheet matches your particular transformer. I would like to know if you can visually tell the two apart. That could be worthwile knowing if someone picks one up at a flea.
  BTW, the size of the file is large and takes a while to download. Try saving the file and then printing it. A printed version is quite easy to read.

Steve: Feel free to add the data sheet to the AM Window.

Bill