Ampex Bridging

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CJ

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Here we have a couple of Ampex 4580200-01 bridging transformers, courtesy of Ciminosound.

1:1 turns, 10 K impedance.

http://vacuumbrain.com/The_Lab/Ampex/ampex_bridging.jpg

There is a slight difference between the black and green base models.

Black Base:
150 H
DCR: 1.44 K
Leakage: 25 mH and 146 pf for a predicted resonance of 82 K CPS

Green Base:
188 H
DCR: 1.44 K
Leakage: 19 mH and 167 pf for a calculated resonance of 88 K CPS

Freq plots were fairly identical, there is a slight shift on the rez peak, as predicted.There was a slight rise at the upper end on one of the units.
So the cores are probably the same, but the coils have to be slightly different.

There's that weird bass rise I see from time to time.
Have not figured that one out yet.

http://vacuumbrain.com/The_Lab/Ampex/ampex_bridging_freq.jpg

B-H was a bit different from the norm:

http://vacuumbrain.com/The_Lab/Ampex/ampex_bridging_bh.jpg
 
What, tear up a perfectly good xfmr?
Have you lost it? :razz:

I think Gerry might want one back, but I could dig tearin up one of these guys.

Going home to think about which one gets the axe.
 
I have one of those, but mine is black.
somewhere here I read that they were used as mic input transformer on ampex mic preamps. but 1:1 10k don´t look like a mic preamp transformer isn´t?
 
:shock: whoa - interesting stuff!

I always wondered how you'd do the winding geometry for relatively high-Z bridging transformers like these.. 2x150H (!) that is quite a bit - and with that low leakage cap/ind - wonder what the trick(s) are...

Jakob E.
 
Lams: 312 EI 27 ea. Probably 50/50.

Structure:
1/2 Sec-Pri-1/2 Sec

Inner Sec - 12 Layers-0.0020" green enamel #44- 2000 Turns
Middle Section-Pri - 24 Layers - 0.0020 green enemel #44 - 4060 Turns
Outer Sec - 11 Layers - 0.0020 green enamel #44 - 1850 Turns

Two shields, between the sections.

So a few new things,

1) The turns are unequal, but this is a 1:1, they should be the same
This means unequal coupling between pri and sec, so this tweaks it into place so you get the same volts out as you put in.

2) Unequal turns on the two sec sections.
Less turns on the outer sec means a little better dcr match up between thew inner and outer sections.

Margins were offset quite a bit, 0.075 on the left, 0.144 on the right.

Pics tomorrow.
Tie game. Still time to catch some action.

cj
 
Wow cool info, thanks CJ :cool:
I have a bunch of these in the 2, 4 and 8 track 440Cs I have scattered around here at the moment, its interesting to know that the different color input transformers are different inside aswell.


M@
 
Alright, deleted the Cannon uploader, found out the twain in my grapghics program does uploads one pic at a time, so tomorrow, reload cannon 800 mb clogg fest. :twisted:

But I did get a lot of pics.

Like this one:

ampex_a.jpg


Remember, torch in the winter, ice axe in the summer.
More comfortable for Hack Masterson!

Always nice to take apart more than one to verify and find differences.
Thanks to the generousity of Ciminosound, I got the OK to hack both!

Differences?
Of course! No two transformers are exactly alike.

The weird unbalanced turns in the first one was probably a winding mistake.
The guy snapped the wire on the last layer, did not want to throw away the whole coil, so he let it slide.
That's why the freq plot resonances are slightly different.

So turns on the first guy were 2000 and 1850 =
3850 Sec and
4060 pri

where as the Green base has 2000 and 2017 =
4017 Sec and
4015 Pri.

See what us hackers go thru?
Some yoyo snaps some #44, then I start thinkin that it's a new design or something! Then I spread it arount the net, then I get busted by a guy with the prints!
Dang winders.

Entrails becoming visible:

http://vacuumbrain.com/The_Lab/Ampex/ampex_b.jpg

Another difference, the BH curve on the green base model is different.
Therefore, the lams are diferent.
You are going to have to go back to post one to compare.

Green BH:

ampex_bh_green.jpg


Extracted carcass.
That square thingy is just to elevate the assy a bit. Pressboard.
Never seen that so kind of neat.

http://vacuumbrain.com/The_Lab/Ampex/ampex_d.jpg
http://vacuumbrain.com/The_Lab/Ampex/ampex_f.jpg
http://vacuumbrain.com/The_Lab/Ampex/ampex_g.jpg

De-lammed:

http://vacuumbrain.com/The_Lab/Ampex/ampex_i.jpg

OK, so the black base model used green wire...
ampex_k.jpg


and the green base model uses....
ampex_red_b.jpg
 
OK, lams are 312 EI
27 Each.

ampex_lams.jpg


The black base lams looke like a different alloy, or it could be things got a little too hot, and the potting compound made it look like that.
But I do know that the something is different because of the BH curves.

Here are both sets of lams side by side:

http://vacuumbrain.com/The_Lab/Ampex/ampex_p.jpg

Another weird first: I found 5 lams that were 0.004 instead of 0.013.

I do not know if they wanted to use up the more expensive and less popular 004 stuff or if it was to make the fit between the coil and lams better, or if it was some weird tweak meant to throw off our hacker minds into turmoil?

ampex_q.jpg


Self explanatory:

http://vacuumbrain.com/The_Lab/Ampex/ampex_m.jpg
http://vacuumbrain.com/The_Lab/Ampex/ampex_n.jpg
http://vacuumbrain.com/The_Lab/Ampex/ampex_o.jpg

The green base model had a copper core contacter thingy inside there.
The black base model did not.

http://vacuumbrain.com/The_Lab/Ampex/ampex_r.jpg

Glass tape on the sides of the finished coil:

http://vacuumbrain.com/The_Lab/Ampex/ampex_red_c.jpg

Copper shield:

http://vacuumbrain.com/The_Lab/Ampex/ampex_red_e.jpg
http://vacuumbrain.com/The_Lab/Ampex/ampex_red_shield.jpg

Margins are important. They set up the leakage and also provide distance from the winding to the core to prevent short outs:

http://vacuumbrain.com/The_Lab/Ampex/ampex_red_margins.jpg

Secondary splice:

http://vacuumbrain.com/The_Lab/Tmpex/ampex_s.jpg

A new way of unwinding.
Much nicer!

Old way, heat the coil, unwind a few layers, counting the turns by hand, write it down on the paper, re-heat, unwind, write it down.

Now, I simply put the heat gun in a vise and unwind interupted, and the turns counter keeps track of everything.

Spoiled now, but hey, I paid my dues!
http://vacuumbrain.com/The_Lab/Ampex/6611.jpg

Thats it.
Thanks again to Gerry.
And I have three more different xfmr's to go from him, so stick around!

Plus the 25 still on death row. :green:
 
Jake, I will do an Al test and see what the grade is.

I did notice the paper between layers was a bit thicker than normal, they specify a certain thickness depending on the wire size you use.
Also, when heated, you could pull the coil apart section by section
The pri slipped right off the sheield at one point. I had to stick it back on there and let it cool.
So this induicates loose winding, in order to get more air between layters.

So the thicker paper and lower wire tension helps keep capacitance down.
 
Just spotted a pair of these up for grabs on ebay.
Auction ends tomorrow and I'd love to bid, but I'm far too broke at the moment.

Here's the link if anyone's interested;
http://www.ebay.co.uk/itm/231697401450?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I've got no affiliation whatsoever to the seller, Just thought I'd post a friendly "heads-up" for you guys about the auction.
 
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