OT Windings

[Jazz P Bass]

Beautiful photo!

[Dave H]

I'll write the long explanation instead of just throwing a naked formula on the table

Naked is fine by me

Doh! I got it wrong all ends up didn't I? I couldn’t even get the wrong calculation right! That’s what you get for posting on autopilot at 3:00 in the morning when you can’t sleep. OK, I think I got it now. Here’s the short version - They’re in series so have the same current therefore power is proportional to R as I^2 is constant.

Thank’s Juan

[J M Fahey]

Actually, I was wondering "where's the card reader?" Those were really cool machines. With all the register lights on the front panel it put on a great display when the machine was running.

Thanks for the links Jazz

Ours had the card reader, of course, but cards themselves were expensive so we poor students who wanted the machine for personal use, relied on their poor cousin: perforated paper tape.

Functionally the same, cheap as dirt, could be rolled up and carried in a pocket.

We typed/punched them, let them inside a signed envelope and hopefully got results a couple days later, depending on queue length.

Results might be another punched tape, if they were intermediate results to be combined with others in a more complex job, or final, human readable ones, printed in "bedsheet" size fanfold paper.

Yes, total modules were about twice what is shown in that picture.

FWIW I still have an IBM 1620 (empty) chassis in my backyard, use it as a table to cut full size chipboard sheet (6' by 12/14') into more manageable chunks.

Languages available were FORTRAN for serious work, BASIC fos smaller student tasks and although the machine could run COBOL we intensely despised it as "Merchant stuff" .

[J M Fahey]

Thanks, I have the time of my life when they both are staying with us. But they both will be going home after New Years!!!

Attached is a picture on my wife's 70th birthday.

Alan

Beautiful picture, beautiful Family.

Congratulations

[Dave H]

My first attempt at programming was done on one of these, a flexowriter. My typing skill was so poor back then (and nothing has changed) that I never got more than a few lines of code to run. I was really more interested in trying to play like Eric on the Beano album and I'm still trying.

[Dave H]

Attached is a picture on my wife's 70th birthday.

Alan

That must be a typo. I'm sure you meant 50th.

[Alan0354]

Thanks guys for complementing on the picture. My grandson Conor is almost 15 and is taller than me. Grand daughter Alena is 8. And no, it's not a typo, my wife just turn 70 in Nov. Finally I am winning the battle with the printer and scanner!!!!

Happy New Year guys.

[Alan0354]

Ours had the card reader, of course, but cards themselves were expensive so we poor students who wanted the machine for personal use, relied on their poor cousin: perforated paper tape.

Functionally the same, cheap as dirt, could be rolled up and carried in a pocket.

We typed/punched them, let them inside a signed envelope and hopefully got results a couple days later, depending on queue length.

Results might be another punched tape, if they were intermediate results to be combined with others in a more complex job, or final, human readable ones, printed in "bedsheet" size fanfold paper.

Yes, total modules were about twice what is shown in that picture.

FWIW I still have an IBM 1620 (empty) chassis in my backyard, use it as a table to cut full size chipboard sheet (6' by 12/14') into more manageable chunks.

Languages available were FORTRAN for serious work, BASIC fos smaller student tasks and although the machine could run COBOL we intensely despised it as "Merchant stuff" .

Ha ha, some of us are old enough that actually used the IBM punching machine and run the card reader for programming!!! I took my first class of Fortran in 75 using that. That was a hassle. You drop the cards, you're really screwed!!!

[The Dude]

My first programming in tech school was on one of these.

[trem]

Sorry but that's not the case.
You think both windings use same diameter wire .
The 4 ohms winding uses half the available turns, but also 40% thicker wire, so half resistance per turn.

And that, in guitar OPT, or general purpose ones; in Hi Fi types (or some Pro PA ones), there are not 4/8/16/whatever windings per se, but a bunch (at least 2 but might be up to a dozen) of independent windings connected to a patch plate, and there you combine them in series/parallel as needed to get whatever impedance.

In that case, it would have 2 x "4 ohms " impedance windings, which are used in parallel for 4 ohms and in series for 16 ohms.



See above.


No, power dissipatedis the same, radiation and convection surface is the same, so temperature rises by the same amount in both.

The only difference is that the 16 ohms coil is lighter than an 8 or 4 ohms one; speaker is not louder but may be snappier, brighter.

Man... THIS (along with a Million other "things") I did not know, but have always wondered about.
Will read it all again, and may have another question(s).
At any rate.....Thank You
Extremely interesting Discussions/Info going on here.

[trem]

My post above .....I had not read past Juan's post in my quote. I see my questions were probably addressed by others. Going to have to print and/or save this thread. Incredible knowledge in all this mess.
I should start another post but.....looking at Juan's old pictures, makes me think back even further in time.
You guys would have been in Heaven at Bletchley Park. Can you imagine.?
Not JUST Bletchley...but that whole 1940's electronics revolution during the war. The sky was the limit for guys with your Knowledge/Education/Intellectual Horsepower.
Alan Turing, Tommy Flowers.....but just in general...all the unknown Techs/Innovators working on RADAR...amplifiers...detection devices of all types...smaller and better batteries...improvement in navigation of all types for Naval and Aviation application.
The ideas (some of them, no doubt, crack-pot) submitted to The War Department must have been endless.
Anyway.....I have rambled.
Thank Again (once again) For All The Expertise

[trem]

Sorry but that's not the case.
You think both windings use same diameter wire .
The 4 ohms winding uses half the available turns, but also 40% thicker wire, so half resistance per turn.

And that, in guitar OPT, or general purpose ones; in Hi Fi types (or some Pro PA ones), there are not 4/8/16/whatever windings per se, but a bunch (at least 2 but might be up to a dozen) of independent windings connected to a patch plate, and there you combine them in series/parallel as needed to get whatever impedance.

Just making sure I read you correctly.....I should pull apart a donor OT some day.
IF I did look at the secondary of a multi-tap guitar amp OT.....the 4 Ohm winding would use bigger AWG Wire...and then be soldered to smaller AWG for the 16 Ohm tap.?
Is that how they are built...just one continuous winding, with a "tap" connected at the proper spot for the appropriate Impedance.?
Thank You

[Jazz P Bass]

As far as I know, that is the proper procedure.

"A tap is nothing more than a wire connection made at some point on a winding between the very ends. Not surprisingly, the winding turn/voltage magnitude relationship of a normal transformer holds true for all tapped segments of windings. This fact can be exploited to produce a transformer capable of multiple ratios"

[Mick Bailey]

Ours had the card reader, of course, but cards themselves were expensive so we poor students who wanted the machine for personal use, relied on their poor cousin: perforated paper tape.

Now, The Facit high speed reader had a really nice 'feature'; it read the tape so fast it could play a note. If you programmed it right it could play a scale. If you spent enough time you could get a tune and stick the tape in a loop. The boredom of mainframe engineering......

[J M Fahey]

the 4 Ohm winding would use bigger AWG Wire...and then be soldered to smaller AWG for the 16 Ohm tap.?

Yes, that's the way.
FWIW I design and wind my own PT and OT and would never even dream of using "one size fits all" wire.

Is that how they are built...just one continuous winding, with a "tap" connected at the proper spot for the appropriate Impedance.?

Not "continuous" as in you use the same wire from end to end.

Of course, sometimes there are practical/convenience considerations in which you do things a little different, but always "erring" in a safe way.

Examples:
a) if the transformer is only 4/16 ohms, you will definitely use different wires.
Otherwise the 4 ohms winding will be too lossy or the 16 ohms one will not fit in the window.
b) now in a 4/8/16 ohms one, unless you are extremely short of window space, you may start with a thicker wire for 4 ohms, continue with a thinner one for 8 ohms and keep it for the 16 ohms tap.
The "wasted" copper, thicker than needed, may be compensated by not needing to carry yet another wire size plus the annoyance of having to set the winder for the still thinner wire.

And going from 8 to 16 is not that many turns: if the 4 ohms tap is 60 turns (think Fender 2x6L6 OT) , the 8 ohms one is 85 turns, or just 25 more ... just 1 layer ... and 16 ohms is just 35 turns more, probably fit in just 2 layers with space to spare, so you might decide to keep using same wire as in 8 ohms.
As you see, electrical specs must be followed but sometimes a little "waste" is not that bad, considering other factors.

Same as when a chassis is punched with more holes than needed, to cover different models, or using the "Reverb model" PCB also for the "non reverb" amp. and so on.