McCurdy Input Transformer-MRI 2001

[CJ]

There comin in faster than I can hack em, so got to stay on top elst be banished for life.

This time it's a fine sounding McCurdy input transformer:

http://vacuumbrain.com/The_Lab/McCurdy/mc_a.jpg

Octal base, of course:

http://vacuumbrain.com/The_Lab/McCurdy/mc_b.jpg

Two pri's, one sec.

Pri A: 17.2 Ω DCR 6 Henries on the B-K Fish, 2300 mH on the Sencore.
Pri B; 17.2 Ω DCR 6 Henries D= 0.682

Sec 40.3 Ω DCR, 19.8 Heries B-K, D = 0.571

8130 mH on the Sencore.

Imp ratio looks like about 1:3.35, which translates to a theoretical turns of 1:1.83.

We will se when we sweep it.

Leakage:

pri to sec - 152 pF
Pri to pri - 128 pF

either pri to shorted sec - 14.9 mH
sec to shorted pri - 55.8 mH

Here's the freq graph.
Something I have not tried but should have with all these dissections, trying sweeps with different pri configurations.

With this xfmr, the best hookup was series pri's.
Flattened out everything to about 100 K.

Worst was pri's in parallel, it was flat, but the res peak was 74 volts at 440 K Hz, compared to 33 volts at 440 K Hz with the single pri hookup.

Single pri was interesting, a rise til 55 K Hz, then a dip, then a bigger rise at 440 K Hz. Not your typical filter response model!

The green line is way off the paper.

No wonder Tommytones likes this thing. It saturates at 1 volt RMS at 20 hertz, and I mean by then, the core is getting hammered.
Mushy nickel can sound good.

Here's the BH:

http://vacuumbrain.com/The_Lab/McCurdy/mc_bh.jpg

OK, noew the fun part!
:twisted:

 

[CJ]

OK, dissection done.

Running late, no pics but:

Lams: 31 UI same as UTC but these are 0.006 thick.
Fist time I have seen a whole transformer lammed with anything but 0.014.
Expensive.

Has to be 80 Ni.

Struture is simple, dual coil, pri-sec- 0.0045-0.0050 wire - #37 ga.

Copper shield between pri-sec.

364 turns - 4 layers for both pri and sec on coil A,

367 Turns 4 layers for both pri and sec of coil B.

Internal splice links pri's in series.

So this is a 1:2 xfmr.

Later!

Pics tomorrow.

Thanks to Tommytones for this beauty.

cj

 

[tommytones]

:green:

 

[jetboatguy]

MRI = McCurdy Radio Industries

although, I do beleive that most of McCurdy trannies were made by Hammond, like the one I see in CJ's pic... and sometimes McCurdy used Beyer trannies in the smaller circuits.

 

[CJ]

Yes, Canada. MacIntosh use to send them transformers and tubes for the MC-30, as an example, and McCurdy would build it to avoid tariffs.
So Hammond (Canada) makes sense, although this build quality is a lot beter than what you see in say, a Hammond pwr trans.

This guy was easy to take apart, at first.
All I had to do was pop the top off with the screwdriver:

But then the darn thing got stuck, so I had to break out the torch:

Here's the reason it got stuck, false bottom for shielding:

http://vacuumbrain.com/The_Lab/McCurdy/mc_g.jpg
http://vacuumbrain.com/The_Lab/McCurdy/mc_h.jpg
http://vacuumbrain.com/The_Lab/McCurdy/mc_i.jpg

I knew the second I saw this lam stack that something was up.
After you stare at 0.014 lams all your life, anything else is easy to spot:

Pri leads on one side...

Sec on the other, with the splice.

http://vacuumbrain.com/The_Lab/McCurdy/mc_L.jpg

Lam type, 0.006".

http://vacuumbrain.com/The_Lab/McCurdy/mc_lams.jpg
http://vacuumbrain.com/The_Lab/McCurdy/mc_m.jpg

Coils without lams, some space left in the window.
High perm core and low turns go together.

http://vacuumbrain.com/The_Lab/McCurdy/mc_n.jpg


1/8 inch copper strip is snipped, bent out and used for the screen hookup:

http://vacuumbrain.com/The_Lab/McCurdy/mc_o.jpg

One of the starts:

http://vacuumbrain.com/The_Lab/McCurdy/mc_start.jpg
http://vacuumbrain.com/The_Lab/McCurdy/mc_u.jpg

A little space between turns.
http://vacuumbrain.com/The_Lab/McCurdy/mc_v.jpg

Screen under the insl:
http://vacuumbrain.com/The_Lab/McCurdy/mc_w.jpg

Last layer is a partial fill, leaving the big margin:
http://vacuumbrain.com/The_Lab/McCurdy/mc_x.jpg
http://vacuumbrain.com/The_Lab/McCurdy/mc_margins.jpg

 

[BYacey]

What ya got there CJ is what looks like a Hammond 800 series transformer. I have a few of these myself. The new versions come in a square can, although the older ones used a round can like you have. These aren't too bad a transformer, but certainly not Jensen equals either.

 

[tommytones]

I wonder if it's like an 800 or not. Hammond used to make a 585 series which was a round can. Definitely does not sound like any 800...much much cooler IMO. Maybe I should send you an 800 to inspect :green: I'm thinking that these McCurdy's are similar to the 585 because to me, they sound different than 800's.

 

[BYacey]

I think you may be right TommyT. I'll have to dig through my parts bin and see what the number is on those cans.

 

[bALLdo]

So no love for the 800 series Hammonds? I've got 8 of the 842's from a McCurdy console, and haven't figured out what to do with them yet. (I'm an electro-newbie). I had hoped they'd be useful for something.

What would one of the MRI 2001's be useful for? I've got one, and I've got a couple of other MRI series in an old McCurdy eq. I'd love to get your takes on them!

 

[jetboatguy]

That style of McCurdy EQ is quite rare... that's all can say ?

 

[rafafredd]

seriously, man.. 842´s are very nice transformers... If you don´t find any use. I´ll be happy to take it.

 

[bALLdo]

I had been thinking of some uses for them. I'm sure they'd be great for something.

 

[CJ]

print for McCurdy MRI 2001  - Hammond 842>

 

[mutterd]

Hey CJ,

thanks so much for posting this - I'm a big fan of Hammond transformers so its nice to see them around here...

and while i cant see the original photos of the Hammond/McCurdy 2001 - for the sake of archival accuracy - the Hammond 842 and the Hammond/McCurdy 2001 don't seem to be drop in replacements for each other.

the Hammond 842 is a +20dBm, 24k:600, Split tap, Push Pull Plate to Line output transformer. And a really good one at that.

So while the 2001 might look the same and share overall and mounting dimensions with the 842, they are quite different electrically.

attached is a data sheet for the Hammond 800 series transformers - if you ever want to poke around any of these, or any other McCurdy branded Hammonds i'd happily donate a select few to science - in particular, the McCurdy 3002 is of special interest to me.

thanks CJ,
Timothy

 

[CJ]

thanks Timothy  i was looking all over for that, 
cj