CJ

Chicago Transformer BO-1 SE OPT
« on: June 19, 2020, 01:01:27 AM »
this guy says Stancor on it, but it also says Chi Town on it,

so it was either sub-contracted out to Stancor, or Stancor was a part of CTC at some point,  i  have seen some Stancor stuff that looked a lot like UTC,   and RCA stuff that looked like UTC,  and RCA tubes that were really Mullard and all that kind of stuff.

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #1 on: June 19, 2020, 01:07:31 AM »
CTC stuff is built like a tank,  only way to get in there is by brute force.

any idea of saving cans or header plates should be dismissed beforehand.

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #2 on: June 19, 2020, 01:10:14 AM »
try  not to cut the coil or core in half. sometimes they are leaning right up against the tank.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #3 on: June 19, 2020, 01:16:32 AM »
we tried to peel this guy apart with just one incision, but the steel was too good,

looks like those DIY  popsicles we used to make, don't taste as good,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #4 on: June 19, 2020, 01:23:18 AM »
see how close that coil was to getting hacked?  it takes the  precision of a skilled surgeon to extract the coil/core assy without collateral damage,  if i had a longer arm i would pat myself on the back.   :D

built like a tank, see how the core is clamped to the can with that bracket?

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #5 on: June 19, 2020, 01:39:07 AM »
the coil/core assy has been liberated from it's domicile,

primary leads (2) coming out on one side,  secondary leads (6) opposite side,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #6 on: June 19, 2020, 01:45:22 AM »
this is a single ended xfmr that can handle some DC, so we need a gap, and probably some regular silicon steel,

this has a partial air gap in that the core is butt stacked in two sections,

there is no paper in the gap.

this will put the core slightly into a regular 3 x 3 lace as far as inductance is concerned, so you gain a little primary inductance and still keep the core out of saturation by way of the partial gap.

how many sections you can get away with without saturation is figured out on the slide rule by some vicious engineer who was trying to support a large Catholic family back in the early 60's.  ;D
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #7 on: June 19, 2020, 01:48:54 AM »
who's up first? looks like a secondary.

so i bet the primary is in the middle somewhere.

outermost section is the worst as far as the black tar is concerned,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #8 on: June 19, 2020, 02:05:00 AM »
nice winding job,   


"fill factor"  is a spec that is sometimes used on winding prints,

it represents who tightly packed the turns are,  there are many different fill factors possible on a precision winding machine, especially the old 60's machines with gear driven cams.

a layer can look like the turns are touching each other, but in reality, it is not feasible to wind coils this way on a multiple winding machine where you have 10 or 20 coils being wound at the same time.

allowing a little space between turns will mean that you will save crossovers on one or more coils due to wire tolerances playing havoc with the winding process,  all wire varies a bit diameter wise as you un-spool it.

so if one coil's wire decides to run .0003" wider than it's next door neighbor, having a fill factor of say. 91% will allow plenty of room so that the thicker wire does not overlap itself.

with a single coil of larger size, you can hand wind it with a higher fill factor.  as you simple hold the wire at a slight angle to the left if winding left to right so that the wire is actually rubbing up against itself . if the angle is too high, you have to stop and rewind the coil to undo any crossovers, this is where the art of winding comes into play, good winders can hear and feel the wire touch as it spools on the coil, too much vibration or noise means move the wire a bit faster to the right,

so you can get less leakage inductance with a hand wound coil. but you also have more capacitance. so fill factor can also be used to control capacitance between turns. however, out of all the capacitances you have in a coil, turn to turn capacitance is usually the least worried about.  layer to layer capacitance plays a more important part in high frequency characteristics.
« Last Edit: June 19, 2020, 02:08:19 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #9 on: June 19, 2020, 02:21:54 AM »
CTC  used varnish instead of wax to impregnate this coil. that means that over time, the insulation in a varnished dipped coil can harden and become impossible to remove layer by layer. heating the coil with a heat gun does not solve the problem.

so the trick is to heat up the coil a bit and pull the thin wire through the paper.
pulling #39 (0.0038") wire through 1 mil Glassine layer insulation is easy if you take your time, but it takes forever to count out 4200 turns like you have  in this guy. sometimes the wire breaks as there are weak spots in the copper along the way, so in order to not lose track of the turns, you have to set the machine to low and take it down layer by layer.


this is the primary in the middle, between two inner secondaries and two outers,
so coil structure is sec-pri-sec.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


rackmonkey

Re: Chicago Transformer BO-1 SE OPT
« Reply #10 on: June 19, 2020, 02:34:53 AM »
Chicago and Stancor were divisions of the same company at some point. I don't know when that happened. But my catalogs from the early 60s are all "Chicago/Stancor".

Been eager to see this one hacked. Thanks for taking the job!
Whether you think you can or you think you can't, you're probably right.

CJ

Re: Chicago Transformer BO-1 SE OPT
« Reply #11 on: June 19, 2020, 03:26:01 AM »
My pleasure! Thanks for sending them!  :D

Here is the print,

CTC does not spec DC current, so we used 12 ma based on a tube chart or a 6C4.

this guy is loafing along at about 3.5 K Gauss at the rated operating level,

so +15 dbm is very conservative however, primary inductance is only about 50 H for a gapped core, still, distortion should be pretty low.

if you know of any circuits where this guy was used i would love to see them!

since we had an open primary, we had to sort of guess at the inductance and DC flux as those specs are based on core permeabillity. and we have to guess at the natural air gap as there was no paper gap installed.   depending on who stacked the core, there will always be a bit of space between the butt stacked sections.

we can rewind the coil with 4232 turns and measure it i guess,

turns ratio indicates about 12.6 K pri Z compared to the 15 K spec, as with the LS-51, these specs can be high or low o the actual turns ratio not counting voltage loss due to DCR.

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

rackmonkey

Re: Chicago Transformer BO-1 SE OPT
« Reply #12 on: June 19, 2020, 03:26:04 PM »
The BO-1 was used in the Fairchild 666. See attached.
Whether you think you can or you think you can't, you're probably right.

CJ

Re: Chicago Transformer BO-1 SE OPT New
« Reply #13 on: June 20, 2020, 11:57:49 PM »
build chart
« Last Edit: June 21, 2020, 12:05:35 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


 

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