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18th June 2018, 02:33 AM  #11 
diyAudio Member
Join Date: Mar 2009
Location: Buenos Aires  Argentina

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Design/make/service musical stuff in Buenos Aires, Argentina, since 1969. 
18th June 2018, 08:15 AM  #12 
diyAudio Member
Join Date: Sep 2012

Diameter of all wires is shown with varnish.
The approximate dimensions of the core are 2668/1998 for Marshall 100W: Set  37 mm Width of the tongue is 41 mm Width of sides is 20 mm Window height is 60 mm Width of the window is 18 mm Thickness of the plates is 0.35  0.5 mm, depending on the year of production. 
20th June 2018, 08:27 AM  #13 
diyAudio Member
Join Date: Oct 2005

using wolpert formula,can someone teach us how dagnall c1998 came up with 620+620 primary.............
np=E x 10^8 / 4.44 x Ac x F x B np=no. of turns Ac=area of the core in sq.in 4.44=constant F=lowest frequency B=flux density lines/sq.in or gauss x 6.45 lines/s.in 
20th June 2018, 09:54 AM  #14 
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Join Date: Sep 2012

We are talking about Marshall, so you have around 460 Vdc B+, that are around 400 Vpp, so 141 Vrms.

20th June 2018, 10:12 AM  #15 
diyAudio Moderator

He's referring to the primary no. of turns, not the B+ voltage...

20th June 2018, 10:24 AM  #16 
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Join Date: Oct 2005


20th June 2018, 12:49 PM  #17 
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Join Date: Sep 2012

jazbo8, there are two ways of reading the messages.
One is reading the messages, the other one is reading between the lines. I perfectly know what engel wants, but due to the book he cited, I also know that Engl already has all the other informations of the formula, except the voltage. That's what I gave him, then it's just a matter of calculating it. 
20th June 2018, 05:07 PM  #18 
diyAudio Member
Join Date: Oct 2005

replicas playing with this data
merren 1.75K 1.5in stack classic tone 1.7K and 2.2K @350v ct @ 290mA sowter 1.75K 50H metropolous plate v 498v Calculate Tube Amp Power Transformer Current here 479v if i knew i would not ask,all i can do is guess even if i tried some of wolpert given figures 
4th July 2018, 05:30 PM  #19  
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Join Date: Jun 2003
Location: Maine USA

Quote:
Many cores listed above are near 38mm square stack. This is 2.24 square inches. Lowest note of guitar is nominally 82Hz. Whether we need full power at 82Hz is a musical question, not engineering. If you have 490V supply you have say 440V peak or 880V pp one side, which is 314V RMS one side. 630V RMS both sides. I am NOT a transformer designer so some of this is WRONG. As an extreme guess, iron can take 10,000 Gauss which seems to be 64,000 lines. Bottom of fraction is 4.44 * 2.24 * 82 * 64,000 is 52,194,509 Top of fraction is 630 * 10^8 which is 63,000,000,000. 63,000,000,000 / 52,194,509 gives 1,207 turns. 1,207 is "exactly" 620+620=1,240 within the coarseness of our assumptions (82Hz, 440Vpk, 10K Gauss). 

5th July 2018, 04:26 AM  #20 
diyAudio Member
Join Date: Oct 2005

thanks prr,
copying is easy understanding what was you are copying was the hardest part, this helps a lot............. If you have 490V supply you have say 440V peak or 880V pp one side, which is 314V RMS one side. 630V RMS both sides. thanks 
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