Maxson Compressor OPT

[shabtek]

This is exciting;
Way More fun than Mary...

 

[mjrippe]

This is so great to see CJ!  Amazing work AND a sense of humor  ;D

Did you find any shorts or breaks?

 

[emrr]

Good work! 

I've got an Atlantic Transformer Co. version of this wind that's good, haven't documented any measurements though. 

 

[Tubetec]

Damn they sure used some weird stuff in transformer winding way back in the day,not sure if a fume cupboard wouldnt be out of place when heat is applied to the funky goo or maybe working outdoors. At first it looked like an oil filled component with the ceramic seals and soldered case . Always worth remembering  PCB's (polychlorinatedbiphenyl) and heat can result in the formation of dioxin, a substance that has no place in living organisms of anykind .

 

[CJ]

now you tell me! 

my best years are behind me, i'm just an old chunk of coal,  so no big.

did not find any shorts or opens,  but a coil that old needs a rewind, modern wire and a bobbin will make it bullet proof.

 

[emrr]

Those 1940's films about how records are made are just a cornucopia of hazardous materials and no human protections in sight. 

 

[CJ]

used to wash my hands with TCE, best hand cleaner in the world, 55 gallon drum on it's side with a spicket, just like a faucet,  :

 

[Tubetec]

My mom used work in the public health system as a dental nurse ,years ago the staff thought it was great fun to play with mercury in their hands ,its mixed with silver powder to form the 'amalgam' which is still used to some extent for fillings . I guess we have the abillity to cross check the safety of anything nowadays with the internet ,they had no such thing back in the day .

I got tired of trying to use lead free solder ,recently  I got a reel of very old stock tin lead rosin cored  ,I knew the moment I smelled that smell I was back to lovely shiney solder joints ,sure theres a downside ,but being carefull and having good ventillation or fume extraction , not breathing  in the smoke,and washing of the hands before eating or smoking reduces any risk by a large factor. When I think back to river fishing as a lad ,we used 'tooth' crimp the lead shot on the line ,and spit  out afterwards ,not something Id do now ,but that was then. I miss fishing alot ,must get back into it .

 

[gyraf]

Thanks, CJ - I so enjoy these show-and-tell of yours...

Jakob E.

 

[PRR]

...it is interesting how the DCR per wire gauge changes over the years, a #29 might 82 ohms per 1000 ft in the old days and now be  65 ohms these days due to better insulation which allows more copper for the same width wire.

Not doubting your historical observations.

But this seems odd.

Copper is more expensive than shellac. Why would they give you more?

The "gauge" is a measure of the *metal*, not the *wire*. You can't hammer a 20 ton pig directly into mike ribbon foil, you have to go in steps. For sheet, the pig is worked to 1/4" slab. Run it through rollers 8 times, you get #8 gauge, good for truck frame; hit it a dozen more times and you get the 20-gauge tin the home-store sells for roofing chicken sheds. Wire starts with 3/8" or 1/4" copper rod, pulled through holes. Two pulls makes #2 wire 0.202" diameter (and rarely used as solid copper). Ten more pulls through smaller holes makes your #12 house-wire. 28 more pulls makes your fine #40.

Some products are painted. If that #20 shed-roof tin had heavy powder-coat, it might measure #19. But there's only a #20 worth of steel in it.

So when measuring gauge you would normally strip all paint/shellac/powder and get down to bare metal.

Yes, the improvement from old-skool shellac/resin to poly-whatzit insulation *does* allow more copper in the same space. This gives several options when rewinding old iron. More turns, or lower DCR, or more interlayer paper... your choice.

 

[rackmonkey]

What’s on your wish list still, CJ? This is too entertaining/informative not to feed the beast if possible,

BT

 

[CJ]

we have a test coil wound with #36, #43 and # 29 wire ,

DCR of original coil vs test coil:

Original :
#37  321 Ohms
#29    6.4 Ohms
#43  2.33 K

Test Coil:

#36  (no #37 in stock)  307 Ohms
#29  5.6 Ohms
#43  3.12 K Ohms

so the #36 we used is actually the right gauge,

the #29 DCR on the test coil is low, so we conclude the original wire was actually #30,

and the #43 test coil resistance was high, so we conclude that #42 was the original gauge,

even gauges are more common for some reason than odd gauges, so this makes sense. micrometer measurements of vintage wire do not match up with modern gauges as far as DCR, this is the reason for the discrepancies, as PRR noted, the bare copper measurements will determine the DCR. The ratio between copper and enamel will be different with modern wire.

So we need to go to a thicker gauge for Pri 1 and Sec 2 and thinner for Sec 1 if we want to match the original coil.

So we will order some #30 and some #42 for the rewind job and keep this coil for a possible DIY Maxson in the future, 

here is the updated print with the tweaked wire gauges>

 

[CJ]

transformer rewind complete, switch to #42 AWG brought DCR down to the original specs,

s wave response on 600 ohm sec>

 

[CJ]

freq response starts to change (phase shift) at about 10K, with the first drop at 17 K just like the original, then it builds back up and is back to normal at 20 K  then about 4 more peaks and valleys on the way to oblivion, 

control winding chokes off completely at 50 K Hz, Bessel style,  but who needs to compress at 50 K? not much of that will reach 600 ohm wind anyway,

 

[CJ]

got the coil wound, steel came in, laced it up Lap 2, put the brackets back on, dried it out at and varnished dipped, then re-bake overnight,

the heat tightens up that glass cloth tape which tightens up the coil, ready to do some hookup,

 

[CJ]

winding machine can be used as a drill press, drilling out the terms after the solder sucker job, got to make room for 18 ga wire,  and also get to  remove any black tar that might have hidden in there, otherwise the solder will not take.

 

[CJ]

ship it!

 

[Tubetec]

Incredible job Cj ,better than new .
Just out of interest ,what did you replace the black gunk with ?

 

[mjrippe]

Beautiful as always, CJ!  Can't wait to install it!