EHT power supply design and construction

<<<<Latest revision @ post #698>>>
http://forum.allaboutcircuits.com/blog/expansions-of-select-abbrivations.765/
LOPT preparation tutorial development
Last action @ 9/17/2016 --- 15:10 UTC


====Introduction====

Scope of series:

Central topics:
This tutorial is one in a (prospective) series with focus upon low ripple, medium current/power PSU solutions for radiography and other modest photon energy (≤ 2 MeV) particle accelerator applications - and, to a lesser extent, exploration of certain 'current intensive' electrostatic phenomena (e.g. electret photography, electret formation, electrokinesis, establishment of electrostatically 'cordoned' (atmospheric) pressure gradients, high volume ion-flow systems, etc...

Peripheral and extraneous topics:
While everyone is welcome to view and post questions (within the confines of this site's TOS/UA) - Please be advised that those having interests confined to the following topics/applications will not likely find this series particularly useful (owing to the availability of significantly less 'labor-intensive' solutions to same):

--'Pedestrian' and 'Quasi'/'Peri'-EHT applications:
(e.g. CRTs, PMTs/Image tubes, Gas discharge devices, lasers, 'negative ion air purifiers', TC primary drivers, GM tubes, etc...)
--Low current demonstration topics (e.g. 'Lifters', 'Jacob's Ladders', 'Plasma Spheres', 'Kirlian photography', 'Ion Motors', etc...)
--Capacitor discharge demonstration: (e.g. 'Quarter Shrinkers'/'Can Crushers', 'Rail/Coil Guns', 'EMP generators', electrical weapons, etc...)

Please be advised that site policy prohibits my response to most inquiries coming under the latter category...
=================================================

Scope of this tutorial
Provision of a minute, 'step by step' procedure for modification of 'heavy duty'
AC LOPTs for 'serious' EHT application/research...

Said procedure having the following principal goals:
-- Improvement of insulation integrity via removal of auxiliary windings coaxial to the EHT winding.
-- Enhancement of versatility via electrical 'floating' of the EHT winding.
-- Appropriate adjustment of reluctance gaps.



The desirability of LOPTs:

Of the commonly available magnetic components applicable to low through medium power EHT production, the LOPT offers the advantages of relatively high power intermittent operation (several hundred to >1kW per transformer) and useful continuous power operation (to Ca. 600 Watts each transformer under forced air cooling). Moreover, LOPTs' amenability to resonant (and, hence, sinusoidal) drive permits development of systems productive of highly desirable mean output EMFs (≈70% peak) as opposed to the rather low (< 1% through 5% 'spike' EMF) characteristic of flyback and similar pulse driven/energy storage topologies. Additionally, the inherent output symmetry attending resonant drive topologies facilitates implementation of effective external EMF 'multiplication' schemes.

Prominent among the LOPT's disadvantages are the common expedient of integral rectification/EMF multiplication circuitry and 'end point' grounding schemes --- While the former objection is readily addressed via judicious transformer selection, the latter requires minor 'reconstruction' - said procedure being the subject of this tutorial.

A few words regarding the unsuitability of DSTs and their ilk:
Principally:
1) Integral components electrically unsuited to general application.
2) Practical impossibility of modification for improved EHT winding to core insulation.

Re: point 1 (above) Although asymmetric drive may permit peak forward (and hence output) EMFs well in excess of the internal rectifiers' PIVs - such is, of course, inapplicable to 'filtered' or otherwise capacitively loaded schemes sans additional external rectifiers - moreover internal rectification greatly complicates cascading of multiple LOPTs for increased EMF and/or development of balanced output schemes...

Re: Point 2
(above)
'DC' LOPTs are constructed as indivisible units sans 'margin' for modification -- moreover (in the case of DSTs) the rectifiers are 'distributed' throughout the winding...

LOPT Selection:
The most desirable transformers are those intended for direct production of (pre-rectified) accelerating potential for large CRTs -- Contrary to 'conventional wisdom' such units are yet readily available from long-established electronics supply houses (whom, in my experience, are only too happy to wave 'minimum purchase' and 'wholesale only' policies at the prospect of disposal of what they regard as 'dead stock') --- That said, one should expect to size their purchase so as to offset the supplier's 'invoicing costs'... Prices ranging from $20 (USD) per transformer (in reasonable quantities) are not uncommon...

The following images are offered as an aid to recognition of the desired form factor:

Assorted LOPTs typical of the desired geometry:
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http://forum.allaboutcircuits.com/attachments/lopts-jpg.101773/

Detail - Axial view:
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http://forum.allaboutcircuits.com/attachments/lopt2-jpg.101772/

Detail - Transverse view:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/nos_tyre_lopt-jpg.101774/


The modification procedure:
--Please do not commence disassembly of the transformer prior to reading and comprehension of the entire tutorial...

=== Part 1 -- Disassembly of the LOPT unit ===


Step 1-1) Identify construction style of LOPT to be optimized.


Task:
1)
Identify construction style via the description most closely matching the reader's device in the following...

Full EMF AC LOPTs feature one of two general construction styles as outlined below:

Style 1)
Features a single piece frame ('clamp') -- the rails of which maintain compression on the core via a single linear ligature fashioned of a metallic strap or bolt extending from frame rail to frame rail across the top of the upper form leg 'facet'.

Example of style 1
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http://forum.allaboutcircuits.com/attachments/lopt_desc-jpg.101778/

Style 2) Features two independent metallic frame pieces OR a metallic half-frame and a backing plate/PCB -- such assemblies are bound by a single "U- bolt"/"U-strap" or two linear bolts/straps extending along the outer aspects of each horizontal form leg...

Examples of style 2


View of LOPT from 'closed' side of "U bolt" ligature
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http://forum.allaboutcircuits.com/attachments/ubolt1a-jpg.101781/

View of LOPT from 'open' side of "U bolt" Ligature
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http://forum.allaboutcircuits.com/attachments/ubolt1c-jpg.101784/

View of LOPT from 'closed' side of "U strap" Ligature
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

http://forum.allaboutcircuits.com/attachments/ubolt2a-jpg.101785/

View of LOPT from 'open' side of "U strap" Ligature
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http://forum.allaboutcircuits.com/attachments/ubolt2b-jpg.101786/

Step 1-2) Removal of form frame ('clamp')

Tasks:
1)
Remove any tape, looped conductors, ground leads, etc. ensnaring/bonding the frame to the form.

2)
Free each end of the frame ligature{s}

3A)
In the case of cylindrical bolt{s} or a cylindrical shaft 'U Bolt':
Remove backing fasteners (i.e. nut{s}/burs{s},etc...) then carefully withdraw the bolt{s} from the assembly.

3B)
In the case of independent strap{s}, or a 'U Strap': Straighten and/or unsolder each fastening 'tab' then splay the frame rails such that the frame 'ears' clear the ligature 'tabs' --Or-- if so constructed, remove the backing plate/PCB from the ligature ends ('tabs').

4)
Remove the transformer (i.e. form and winding assembly) from the framing/clamping/mounting components -- please retain the frame and all associated hardware!

Image of transformer following removal from a single strap-ligature frame:
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http://forum.allaboutcircuits.com/attachments/loptdesc2-jpg.101780/


Annotated image of assembly features referenced in following steps:
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http://forum.allaboutcircuits.com/attachments/annotated2-jpg.110920/

Step 1-3) Procedure for removal of strap ligature{s} from LOPT core/winding assembly:


Tasks
1)
Meticulously straighten and deburr exposed segments of the frame ligature{s}.

2)
Carefully 'work' the frame ligature{s} free of the adhesive, then withdraw it/them from the space intervening the form and winding (and, hence, from the assembly) -- Under no circumstances apply counter-thrust or torque to the EHT winding!

Ligature partially withdrawn from assembly.
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http://forum.allaboutcircuits.com/attachments/loptligwdr-jpg.101790/

Ligature (in foreground) fully withdrawn from assembly.
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http://forum.allaboutcircuits.com/attachments/loptligout-jpg.101789/

Note: Inasmuch as same will be removed and discarded in later steps, damage to the external auxiliary windings (i.e. those on the form leg opposite the EHT winding) or coaxial auxiliary windings immediately adjacent to the core/form leg is of no consequence -- Care must be exercised, however, to avoid damage to the brittle ferrite form/core via excessive force or mechanical shock... Also - avoid handling the assembly by the EHT winding!

Step 1-4) Removal of external auxiliary windings from 'lower leg':


Tasks:
1)
Using an appropriate scalpel, 'X-Acto knife' or similar implement, linearly section the full length of the external Aux winding assembly. --- Again, the referenced winding resides on the form leg opposite that carrying the EHT winding!!!

2)
Peel, crumble and/or break the 'external' Aux windings off of the lower form leg.

Step 1-5) Separation of form pieces


Caution: In performance of the following tasks, it is of paramount importance that neither torques nor linear forces are applied to the EHT tyre! -- Moderate forces may be applied to the auxiliary shell and moderate compressive force may be applied to the ferrite form longitudinal to the EHT winding 'leg' only!

Tasks:
1)
Endeavor to remove (or loosen) any shims intervening the form and inside surface of the auxiliary sleeve -- While damage to the auxiliary sleeve or winding is of no consequence, care must, nonetheless, be exercised to avoid breakage of the form!

Image of wooden shims (indicated by pick)
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http://forum.allaboutcircuits.com/attachments/loptshim-jpg.101791/

2)
Using a #3 sharp fenestrated uterine curette, or similar non-ferromagnetic stainless steel instrument, carefully 'clean' the lower form leg of superfluous epoxy -- Note: Use of razor blades or other ferromagnetic or 'soft' metallic instruments will likely 'foul' the ferrite via metallic transfer to same!

3)
Submerge the lower leg of the form (prepared as per task #2 above) in acetone for a period of ≈ 90 minutes at 7°C (45°F) through 33°C (90°F) - Note: the EHT winding assembly must not be submerged, splashed or otherwise wetted with acetone! - nor should acetone be allowed to condense on same! Owing to the flammability of ketones, said procedure is best preformed in open air or in an open container 'under' an OSHA (or jurisdiction-equivalent authority) certified fume hood (caution! - this does not include 'range-hoods', 'range fireplaces', 'walk-in fireplaces' or their ilk!) -- Moreover, a closed container is not recommended owing to liability to condensation...

4)
Upon removal of the lower form leg from the acetone bath, drive the reluctance spacer out of the lower form joint using an appropriate feeler gauge leaf --- Note that during and following removal of the reluctance spacer/adhesive from the lower form joint, application of even moderate constrictive or distensive forces to the form will result in significant cantilevered forces at the upper form joint with (almost certain) breakage of one or both form pieces.

Of special concern in this regard:

A) Do not attempt to expand the gap while removing the spacer! -- The leaf thickness must be less than the gap width. Maintenance of a parallel relationship between leaf and form piece ends (i.e. gap 'walls') is imperative!

B)
Following removal of the spacer, take care to avoid application of constrictive/distensive forces or piece-to-piece torsion to the form! -- The safest handling method is manipulation of the assembly from one 'side' (i.e. by one form piece) only!

Note: Following clearance of the lower form joint of its reluctance spacer and adhesive, continued half-to-half form tenure owes to the upper form joint adhesive (at the center of the EHT winding assembly) - and, to lesser extent, adhesion of each form piece to the form sleeve of said assembly.

5)
Using a 'heat gun', play a stream of hot (≈200°C /400°F) air in a swiftly alternating, sweeping pattern upon each 'form rail' taking great care to avoid directing said stream upon the EHT winding tyre! - In this fashion gradually and evenly increase the temperature of each 'rail' to ≈ 100°C / 200°F.

6) With gloved hands, grasp form rails (each to a hand) then apply torque (not to exceed 5.5 N⋅cm!) axial to the upper form leg.

A) If/when form-rail to form-rail angular motion is evident, continue rotation until the pieces rotate freely relative to the form sleeve -- If necessary, the form sleeve may be used as a 'counter torque' but under no circumstances apply force of any kind to the EHT tyre!

B) In the event that relative angular motion is not discernible following 30 seconds' application of torque, repeat Task #5 (above) but heat the rails to ≈ 150°C /260°F then promptly repeat task #6 (above).

c) In the event that, having begun to move, sustained rotation becomes impossible prior to 'defeat' of the adhesive, repeat steps 5 and 6 (above) exactly as presented.

7) Carefully 'work' each form piece free of the form sleeve -- Again, avoid application of thrust or torque to the EHT winding tyre!

8) Thoroughly clean the form pieces of adhesive residue via 30 minute's immersion in acetone followed by scrubbing with an acetone wetted cotton cloth.


=== Part 2 -- modification and reassembly of LOPT unit ===

Here we will consider four (coaxial) features of the EHT winding assembly:

To Wit:
(Peripheral to central).
1) The EHT 'tyre' (comprised of the EHT winding proper, potting material and bunting).
2) The Auxiliary shell (a paperboard or polymer 'collar' intervening the central aspect of the EHT winding and the peripheral aspect of the Aux winding...
3) The Aux Winding{s}.
4) The form sleeve (intervening the central aspect of the Aux winding and the ferrite form).

Please note said features in the image below:

Image of unmodified EHT winding assembly.

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http://forum.allaboutcircuits.com/attachments/i1_1-jpg.101749/


Step 2-1) Locate the lug carrying the EHT return:

The EHT return generally emerges with one or more AUX leads from the peripheral circumference of the AUX winding whence they are tied to a shell lug...

In the case of the demonstration transformer, said lug occupies the 2-o'clock postilion -- The image below shows said leads emerging from the Aux winding immediately below the CCW edge of the lug (as indicated by the ball-point pen) -- of special significance is the extreme peripheral position of the break-out point.

Image of the bundle containing the EHT return.

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http://forum.allaboutcircuits.com/attachments/i1_2-jpg.101750/

Step 2-2)
Separate and identify the EHT return:


Tasks:
1)
Carefully unsolder all leads from the lug identified in Step 1 (above).
2) 'Untwist' and otherwise separate said leads.
3) Using a resistance indicator, check each lead for continuity to the EHT output contact (i.e. 'output tower') --- the return lead will show a resistance of between 400Ω and 1000Ω -- All other leads should show infinite resistance.

In this case three leads were tied to the lug -- the resistance examination identified the 38 AWG lead as the EHT return (said lead indicated by the pen in the attached image).

Image of separated EHT return --- Note that the associated lug was broken out of the way.

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http://forum.allaboutcircuits.com/attachments/i1_3-jpg.101751/

Step 2-3
) Removal of the form sleeve:

Please note:
Far and away the most significant challenges attending this procedure owe to the 'gossamer' nature of #38 and #40 AWG conductors... From this point onward it will behoove the reader to remain mindful of the EHT return whenever handling the assembly - while a severed or broken return lead is not necessarily 'fatal to the cause' - such will greatly complicate matters via the requirement of 'teaseling out' the end of a #40 or even #42 (AWG) lead from the lacquered winding!

Tasks:
1)
Carefully dress the return lead out of 'harm's way'.
2) Twist, pry and/or break the form sleeve out from the center of the Aux winding.

Image of EHT winding following removal of the form sleeve. Note the EHT return at ~ "2 O'clock"

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http://forum.allaboutcircuits.com/attachments/i1_4-jpg.101752/

Step 2-4)
Remove the AUX winding:


Precautions:
A)
While 'unraveling' the Aux winding, apply counter-thrust only to the shell --
as opposed to the tyre!
B)
While debriding residue from the 'central gap' following removal of the Aux Shell - great care must be exercised is damage to the central layer{s} of the EHT winding to be avoided!

Tasks:
1) Cut all leads attached to all remaining lugs.
2) Using a surgical pick or similar instrument, pry a few 'layers' of the Aux winding into the center such that they may be grasped with forceps.
Image of Aux winding prepared for removal.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i1_5-jpg.101753/

3)
Grasp the the loosened layers and begin withdrawing ('unraveling') the Aux winding -- Taking great care to avoid application of tension to the return lead as the periphery is approached.

Image of Aux winding in an intermediate stage of removal.

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i1_6-jpg.101754/

Note: The EHT return will typically be 'laminated' between the penultimate and ultimate layers of the auxiliary winding bunting.

4)
Cautiously break (not tear!) the bunting material away from the return lead.

In the image below you may observe the end of the EHT return (as per the pen) and its emergence from the bunting in the gap intervening the shell and the deflected bunting medial to the remaining lug at 4 O'clock

Image of EHT return embedded in peripheral Aux winding bunting.

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i1_7-jpg.101755/

Image of EHT winding following complete removal of Aux winding

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i1_7-jpg.101755/

Step 2-5) Remove the AUX Shell:

Tasks:
1)
Carefully break, crumble and/or fold the auxiliary shell into the 'central gap' via symmetrical application of force to the distal aspects of the former at quadrature to the plane of the return's emergence.

Under no circumstances attempt to pry the shell from the interstices!!! Doing so will almost certainly damage the EHT winding beyond repair!

2)
having thus loosened the shell, carefully remove the fragments being ever mindful of the return...

Images of the EHT winding following removal of the auxiliary shell...


vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_1-jpg.101757/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_2-jpg.101758/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_3-jpg.101759/

Image of EHT winding and debris following removal of the form sleeve, Aux winding, and Aux shell:

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_4-jpg.101760/


Note:
Should the reader's EHT winding be potted in silicone (as opposed to merely 'jacketed' as in the case of the demonstration transformer) it will be desirable to arrive at this juncture sans disruption of the potting material -- Should a breach occur, prompt repair via application of electronics grade RTV is advisable...

Step 2-6) Preparation of The Dummy Shell:

Note: Owing to the 'brittleness' of 'Purell' grade polypropylene, use of a sharp instrument is recommended!


Tasks:
1)
Excise the base of the polypropylene pharmaceutical vial.
2) Section the (resulting) cylinder longitudinal to its axis.
3) Temporarily mount the dummy shell on the ferrite form -- Verify end clearance ≥ 5mm (form pieces in firm apposition). If end clearance < 5 mm, trim the dummy shell to 'compliance' but try to keep end clearance < 1 cm.

Image of prepared dummy shell

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_5-jpg.101761/


Image of correctly 'trimmed' dummy shell on leg of LOPT ferrite form:

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_6-jpg.101762/

Step 2-7) Prepare Return Lug:
Tasks:

1) Form a #4 solder lug such that the 'tab' is at a right angle to the plane of the fastener surface.
2) Drill a #66 (~0.83mm) hole through the lug immediately above the bend.

Image of properly prepared lug -- Note the small (#66) hole near the fastener angle.

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_7-jpg.101763/

Step 2-8)
Installation of the dummy shell:


Image of EHT winding at this juncture - note return lead:

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_8-jpg.101764/

Tasks:
1) Furl the dummy shell, then position it in the central gap from the side of the winding opposite the emergence of the return lead such that the 'cut' faces opposite the output 'tower'.
2) Using a stylus, scribe, etc - mark the dummy shell at the point 5mm (back) from the edge lateral to emergence of the return.
3) Carefully remove the dummy shell.
4) Using a drill bit commensurate with a #4 bolt, bore through the dummy shell at the point marked in task #2.
5) Liberally coat the dummy shell and gap surfaces with electronics grade RTV. -- Avoid application of RTV to the return lead!
6) Reinstall the shell as described in task #1, taking care to position the cut opposite to the output 'tower', and the bolt hole lateral to the emergence of the return lead.
7) Mount the EHT winding/dummy shell assembly on the ferrite form.
8) Adjust the (linear) position of the winding tyre on the shell such that the former is equidistant from the form piece angles while the end of the shell emerging from the 'return lead side' of the winding tyre extends as far as possible from the winding sans contact with the form piece.
9) Remove the form from the assembly taking care not to alter the relative position of the shell/winding.
10) Manually expand the shell as much as possible -- smooth and 'touch-up' the silicone... --- Again keep the return lead free of adhesive!
11) Allow RTV to cure for at least 72 hours at temps of 7.2°C (45°F) through 15.5°C (60°F) -OR- for at least 48 hours at temps >15.5°C (60°F)

Step 2-9) Installation of the Lug and connection of the return:
Tasks:

1) Carefully insert the #4 bolt from inside the shell.
2) Secure the lug to the top of the shell as shown in the images below.
3) Solder-tin the end of the return lead.
4) Insert ~ 2 mm of the return lead into the #66 hole near the base of the lug then secure it with solder.

Note: It is imperative that the return lead is neither trimmed nor glued at this point! - Please loop any slack as shown in the images.


Images of the assembly; Dummy shell & Lug installed, return connected:

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_9-jpg.101765/

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i2_10-jpg.101766/

5)
Verify that the DC resistance (lug to output tower connector) -- is that measured in step #2-2, task#3

Step 2-10)
Prepare the CPVC Form sleeve:

Tasks:
1) Cut a length of 3/4" (id) CPVC tubing equal to the total length of the form-leg on which it will be placed (In the case of this demonstration 8.5 cm) See the two images immediately below...

Image illustrating desired sleeve dimension

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http://forum.allaboutcircuits.com/attachments/i3_1-jpg.101767/

Image of form and adjacent CPVC section cut as per task #1

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/i3_2-jpg.101768/

2)
Cut 'shoulder stirrups' into the CPVC Sleeve:
Note: the stirrups must be sufficiently deep as to allow a slight amount of end-clearance when mounted upon the form (such that form piece apposition is assured).

Image of form pieces and 'prepared' CPVC sleeve
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http://forum.allaboutcircuits.com/attachments/i3_3-jpg.101769/

Image of form and CPVC sleeve in an intermediate state of assembly

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http://forum.allaboutcircuits.com/attachments/i3_4-jpg.101770/

Image of (temporary) fully assembled form and CPVC assembly

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http://forum.allaboutcircuits.com/attachments/i3_5-jpg.101771/

Step 2-11)
Permanently install CPVC form sleeve in EHT winding assembly:


Image of components referenced in this step:
(L to R) CPVC sleeve, EHT winding assembly, Form [core] pieces

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/1-jpg.101711/

Tasks:
1)
Assemble EHT winding, CPVC sleeve and form as shown (below).
2) Using PTFE shims, center EHT winding assembly about CPVC sleeve (both sides).
Note: While the adhesive does not bond PTFE it is, nonetheless, essential that the shims be so formed as to preclude (interlocked) captivity in the former!

Images of mounted and centered EHT winding as seen from 'EHT return side':

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/2-jpg.101712/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/3-jpg.101714/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/5-jpg.101717/

4)
Using acrylic-based 'hot-melt' adhesive, tack the CPVC sleeve to the polypropylene shell at several points each side.
5) Remove form pieces.
6) Fill the space intervening the CPVC sleeve and the PP shell with acrylic-based 'hot-melt' adhesive taking care not to disturb the relative positions of said structures!
7) Allow the adhesive at least 60 Minutes to cool/cure.
8) Withdraw the shims.

Image of assembly immediately following withdrawal of shims as seen from EHT return side.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/7-jpg.101719/

9)
Fill the 'shim gaps' with acrylic-based 'hot-melt' adhesive.

Image of EHT winding assembly following completed installation of CPVC sleeve.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/8-jpg.101721/

Identification of components referenced in steps #12 through #15 (inclusive):

1) PTFE insulator.
2) EHT Winding assembly.
3) Form pieces.
4) LOPT Frame.
5) Polyolefin (heat shrink) sleeves.
6) Elastic cushions.
7) Frame ligature.
8) Form standoffs.
9) Reluctance gap spacers (see text).

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/lopt_partsnum-jpg.101730/

Step 2-12) Prepare form guides


Prior to proceeding, it is imperative that the form pieces are absolutely free of adhesive residue, etc!

Tasks:
1)
Trim two pieces of polyolefin tubing such that they extend the full inside length of each 'winding leg' of the assembled frame (as shown below).
2) With the sleeves in place on the form, clamp or otherwise place form pieces in firm apposition with close attention to alignment of same.
3) 'Heat-shrink' the polyolefin tubing -- Note: expeditious completion of this step will significantly reduce liability to ferrite breakage (secondary to uneven application of heat) and/or permanent shift of magnetic properties (secondary to excessive temperature)...
4) Allow at least 20 Minute 'cool down' period then carefully disassemble the form such that the heat-processed polyolefin tubes remain installed on each 'half-leg' of a single piece.
5) Trim another sleeve then repeat the above procedure such that one leg is bound by a double layer of polyolefin.

Image of assembled form 'sporting' the unprocessed polyolefin sleeves (Post task #1)
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/preshrink-jpg.101742/

Image of form piece following processing of sleeves (Post task #4)
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/separated1-jpg.101743/

Image of form piece following processing of second sleeve on (arbitrarily chosen) EHT winding 'leg' (Post task #5)
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/separated2-jpg.101744/

Step 2-13) Fashion and place reluctance gap spacers
Note: Reluctance gaps will be incorporated to reduce liability to saturation (in all cases) and to leave the transformer compatible with 'flyback' drive topology should same be desired... --- That said, this series prefers forward transfer paradigms (as explained in the introduction to this tutorial).

Note: The (.95mm) reluctance gap spacers salvaged from the disassembly process are shown in the "component identification image" for completeness of presentation only --- Based upon core material properties and desired output current, optimal operation requires development of reluctance gaps consistent with the inequality: 0.25mm < Gap < .5mm -- To this end 0.4mm (nominal) PTFE sheet stock will be used.

Tasks:
1)
Cut two small disks of PTFE having maximum major axes slightly less than that of the form piece 'ends'...
2) Check actual spacer thickness with a digital caliper -- then verify with a mechanical micrometer.
3) Very lightly smear one side of each spacer with electronics grade RTV.
4) Place each spacer (RTV side down) flat upon each form piece end (inside each polyolefin sleeve).
5) Via firm tamping with a pencil eraser or similar implement assure that the RTV film 'tacks' the spacers to the form piece ends...

Images showing representative spacer and measurement of thickness:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/airgapcal-jpg.101725/
http://forum.allaboutcircuits.com/attachments/airgapmic-jpg.101728/

Image showing correct pre-assembly placement of spacers:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/airgapinplace-jpg.101727/


Step 2-14) Assemble LOPT

Tasks:

1) Tack elastic cushions and form standoffs to frame then position as shown:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/loptframechoks-jpg.101732/

2)
Verify that the reluctance gap spacers are fast to the form piece.
3) Hold the frame ligature in lengthwise apposition with the utmost facet of the form's EHT winding leg. (i.e. the leg carrying a double thickness of polyolefin).
4) Carefully place the EHT winding assembly over the form piece leg and ligature such that the shoulder stirrup engages the form piece as shown below:

Form ligature in pre-assembly position:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/asm1-jpg.101729/

Views of EHT winding, form piece and form ligature in intermediate state of assembly.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/lopt_preasmby-jpg.101731/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/loptpartialasmby-jpg.101735/

5) Slowly press the opposite form piece into place allowing time for displacement of air from the polyolefin tubes.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/loptpreframe-jpg.101737/

6)
Install transformer assembly into frame such that the ligature strap ends extend through the 'ears' of the frame.

7)
Very carefully but firmly clamp the assembly preparatory to fastening...
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/loptpresoldered-jpg.101739/

8)
Solder ligature ends to frame
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/loptpostsoldered-jpg.101736/

Step 2-15) Install lateral insulator


Tasks:
1)
Form a cardioid of 0.093" (AKA "93/1000'ths") PTFE sheet stock as per item #1 in the image (immediately below):
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/lopt_partsnum-jpg.101730/

2)
Size, shape and fit the insulator to the EHT winding assembly in a manner consistent with the following images but do not apply adhesive at this time.
Note that the insulator must be trimmed to closely fit the shell and extend beyond the peripheral aspect of the EHT winding by at least 1 cm.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/final-jpg.101745/
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
http://forum.allaboutcircuits.com/attachments/strikeshldside-jpg.101748/

3)
Having properly formed the insulator, 'de-gloss' one side of same using '00' grit emery cloth/paper.
4) Apply liberal quantities of electronics grade RTV silicone to the appropriate surfaces of the EHT winding assembly and the entirety of the 'sanded' side of the insulator.

5) Attach the insulator to the EHT winding assembly as shown in the above images.
6) Apply an excess of electronics grade RTV to the exposed side of the insulator and adjacent areas of the EHT winding assembly...
7) Distribute the RTV over the insulator and EHT winding assembly surfaces such that an interlocking bond is established.
8) Position the LOPT 'insulator up' then allow at least 48 hours curing time.
 
Last edited:
HP I've done first pass of proofing so plz finish disassembly instructions and ending so I can do final pass:)
OBTW I've made recommended changes to my copy (which is post 609) except for 15 and 17 cuz they are points of style

Here's proofreading log
1 Needs “<=” instead of just “=”
2 It’s clearer to just say frame ears cuz slots are in frame.
3 “assembly{s}” can be deleted cuz only one is possible in description and its back referenced in parenthetic clause so its redundant anyhow.
4 “From the assembly” fits sentence better than “off of the form”.
5 “Inside surface” makes more sense than “central aspect” in this case.
6 To correct misdisplaying punctuation character.
7 In this case “through” is clearer than “-“ which can be confused with negative sign.
8 To fix ambiguous subject to lower form leg.
9 HP you need to finish core disassembly instructions!
10 Clarification of relative reference.
11 To correct two instances of misdisplaying omega symbol
12 HP I say is better to say “resistance examination” than “continuity examination” otherwise some ppl might use dmm in cont mode which says everything >300 ohms is open!
13 Clarification of relative reference
14 Clarification of relative reference
15 HP IMO “medial” is ok there cuz “central to” is just lame so I left it be but wanted you to know I looked at it
16 Clarification of relative reference
17 HP I get it but some ppl will misread that word and if they’re too busy snickering or thinking up jokes then they’re not paying good attention.
18 For inappropriate capitalization of “form”
19 To bold very important point that it has to be ELECTRONICS grade silicone
20, 21, 23 Removed “-“ from “end clearance” to prevent confusion
22 To repair misdisplaying inequality symbol
24 Clarification of relative reference
25 Clarification of relative reference (distal vs axial)
26 Bolded “electronics” to emphasize electronics grade RTV
27 Clarification of relative reference (distal vs axial)
28 To correct inappropriate capitalization on “Dummy Shell”
29 For all of task 11 added Centigrade/Celsius temps as default for more universal accessibility;)
30 To correct w/w error (“the” vs “this”)
31 Removed “-“ from “form-piece”
32 Added “permanently” qualifier to avoid confusion from “temporary” qualifier in earlier image description
33 To correct spelling error
34 To repair spelling error
35 Specified “digital”caliper to be clear
36 To emphasize electronics grade RTV
37 Replaced “siliconed” with “RTV” to enhance formality
38 Deleted duplicate word “the”
39 Added omitted verb “be”
1 - Done
2 - Done
3 - Done
4 - Done
5 - Done
6 - Done
7 - Done
8- Done
9 - I'm well aware of that - Thank you!:rolleyes::)
10 - Done
11 - Done
12 - Done --- Excellent point! - Many thanks!:):):)
13 - Done
14 - Done
15 - Agreed (Addressed via re-wording)
16 - Done

17 -- Re: "Labra"
17 HP I get it but some ppl will misread that word and if they’re too busy snickering or thinking up jokes then they’re not paying good attention.
Ironically, the 'proximate' word you're concerned about would have better suited the context - Thus it is that I'd already made concessions to 'those of puerile sensibilities':rolleyes: That said your point is well taken -- hence:
17 - Agreed (addressed via rewording)

18 - Done
19 - Thank you! -- Done with even greater emphasis than suggested:cool:
20, 21, 23 - Done
22 - Done
24 - Done
25 -Done
26 Done as per flag 19:)
27 - Done
28 -Done
29 - Good idea! - Done!
30 - Done
31 - Done
32 - Done
33 - Done
34 - Done
35 - Done
36 - Done as per flag 19:cool:
37 - Very nice!:cool: -- Done!
38 - Done
39 - Done

All the best
HP:)

 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
HP tnx! I'm glad you appreciate all my effort:)! HP I talked to JC today and he says he'll be back later on tomorrow so it looks like we'll all be set for launch when it's ready:cool:!
 
@Aleph(0) , @Jazz2C et al.

Just so's ya know I'm 'on it' -- I've only just affected several additional edits to the tutorial (Post #625) -- I plan to begin completion of said document later today -- While it will not be completed by tomorrow it WILL be finished this month!:):):)

Very best regards
HP:)
 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
HP I can't find it on AAC but somewhere you posted that repurposing refrigeration compressor for vacuum pump is bad idea? I get it abt lubrication but what else was problem?
 
HP I can't find it on AAC but somewhere you posted that repurposing refrigeration compressor for vacuum pump is bad idea? I get it abt lubrication but what else was problem?
Really! I don't know where to begin!:rolleyes: --- Among the many objections is the fact that the internal electrical insulation scheme 'counts on' hyperbaric conditions -- Hence we might reasonably expect hypobaric operation to result in low intensity electrical discharge with consequent 'NOx' formation, thence highly corrosive HNO2 and HNO3 by way of hydrolysis of same via the inevitable condensate --- That said, inundation with condensate will likely 'catch up' with the machine prior to its succumbing to said 'low PH woes':rolleyes:

The real question is why would you even consider such a scheme?!:confused: --- Quality high-volume mechanical 'deep-vacuum' pumps (Speced/guaranteed to < 10 microns Abs) may be had for ≈1,000 (USD) --- $1,000 isn't going to break anyone! --- To Render JC -- "Jeebus"!:D:D:D:D Which reminds me - @Jazz2C if you want to be a bona fide part of the EHT PSU effort - we need to hear from you HERE (as opposed to email/SMS, etc...:rolleyes:)

Best regards
HP:)
 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
The real question is why would you even consider such a scheme?!:confused:
HP It's not my idea! I just wanted more than my opinion to convince Andy not to bother with it cuz I say one more electrical fire and Lisa will leave him for good! Then I'll have two big babies crying in their beer to console:rolleyes: HP I can almost like being thought of as mad scientist but not so much a social worker:rolleyes:!

$1,000 isn't going to break anyone!
Probably not but I say it would back some ppl up a few squares and make them sit out a turn (ya there JC:D?)

HP if you really want to get tutorial done this month you better get busy on unfinished disassembly instructions and closing cuz there's a lot of fiddly BS to do after that! HP I say tool addendum should be put in your blog and linked wherever hard to find tool is referenced in text? Also how abt instructions to build analog EHT voltmeter? Should that be put in addendum or be subject of mini-tutorial?
 
cuz I say one more electrical fire and Lisa will leave him for good!
FWIW I think it was her fortnight's prostration following his bright idea (pun intended!) of interior lighting via Hg vapor lamps minus their borosilicate bulbs that was the 'penultimate straw', as it were! -- IMNSHO photokeratitis has got to compare unfavorably with even infidelity as regards maintenance of 'connubial bliss':eek::rolleyes: -- But yes! Those late-night fire calls have to take their toll as well! -- Sleep is somehow more restful granting reasonable expectation of seeing another day (Go figure:confused::rolleyes:)

Dedicated to Lisa and Drew
(Sorry, I can't resist):D

Probably not but I say it would back some ppl up a few squares and make them sit out a turn (ya there JC:D?)
$1000 no -- loss of his online gaming console (Xbox?), however, would require crisis intervention followed by at least six month's inpatient psychiatric care:eek::eek::eek::rolleyes:

HP if you really want to get tutorial done this month you better get busy on unfinished disassembly instructions and closing cuz there's a lot of fiddly BS to do after that!
I'll be at it ASAP if not sooner!:)

HP I say tool addendum should be put in your blog and linked wherever hard to find tool is referenced in text?
Sounds like a plan!:)

Also how abt instructions to build analog EHT voltmeter? Should that be put in addendum or be subject of mini-tutorial?
Instruments intended for up to 250KV (DC) 'single ended' measurement are readily available and rather inexpensive (I'll post links later) -- That said, construction advice for balanced units may be warranted...

All the best
HP:)
 
Last edited:

Jazz2C

Joined May 27, 2016
52
@Jazz2C if you want to be a bona fide part of the EHT PSU effort - we need to hear from you HERE (as opposed to email/SMS, etc...:rolleyes:)
Hp my interest in helping with the courses is totally genuine! It's just that I'm up to my ears with this that and t'other right now!:rolleyes: I want to work out a schedule that allows me to devote at least an hour or so a week here but I can't make any promises at this point. But you have my word of honor that games aren't taking me away from anything!:)
 
Hp my interest in helping with the courses is totally genuine! It's just that I'm up to my ears with this that and t'other right now!:rolleyes: I want to work out a schedule that allows me to devote at least an hour or so a week here but I can't make any promises at this point. But you have my word of honor that games aren't taking me away from anything!:)
As stated on several occasions, I neither expect nor request that your activity on this thread in any way competes with your studies! -- quite the contrary! -- If, however, you wish to be part of the tutorial development team you'll need to 'carve out' some time from your leisure hours! -- Moreover your 'Who am I to correct HP' refrain isn't going to fly!:rolleyes:

Sincerely, welcome back!:)

Best regards
HP:)
 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
@Aleph(0), @Jazz2C et al.

This is to advise you that I 'm working towards completion the tutorial (post #625) via 'edit' -- When you find a moment, proof-reading/feedback would be greatly appreciated!:)

Best regards
HP
HP I'll proofread it when it's totally done cuz otherwise it never will be! For now I can just say that some ppl might get confused abt N-cm cuz Newtons are less familiar than force units which are also used for mass! Just saying. Anyhow I like how you finished the disassembly details so now it's just finishing the tutorial and doing the glossary and we're all set:)!
 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
HP did you see my actions on your AdvoSci physics forum regarding thread abt bobbing bird novelty? I say you should pull SuperMod status from idiot RynT_ _ _ cuz he's ignorant of basic principles and needlessly rude to posters! For example he said when air and water are same temp that bird gets energy from disassociation of water:rolleyes: When any ordinary moron knows dTemp is just from evaporative cooling of wet fabric on beak! That's why I showed them it couldn't work when RH is too high or with novelties that expect water temp lower than air temp! HP I know you are open minded to some of Keely's ideas and all that but I also say Super Mods shouldn't ridicule newbies to push fringe ideas in favor of common sense! Anyhow I took the liberties of reinstating banned posters and putting lockout on Ryan's SM account until you sort it out:rolleyes: Sry cuz I know you're busy enough already:(
 
some ppl might get confused abt N-cm cuz Newtons are less familiar than force units which are also used for mass!
Then 'some people' require further study in the physical sciences! -- As stated upon many occasions I refuse to 'teach down' to anyone! While I'm sensitive to the inevitable confusion attending injudicious use of idioms, colloquialisms, etc. -- I assert that accepted terminology will pose no difficulty to those possessed of the fundamental cognitive 'prerequisites' for appreciation of the material offered here -- Please note that, as per your suggestion, I have eschewed 'rigorous' mathematical treatment (i.e. via analysis, vector algebra, etc. {Albeit that may need to change in future editions}) -- Hence the 'bar' is rather low as it stands -- let's not make it subterranean!:rolleyes:

so now it's just finishing the tutorial and doing the glossary
No kidding?:rolleyes:

HP did you see my actions on your AdvoSci physics forum regarding thread abt bobbing bird novelty? I say you should pull SuperMod status from idiot RynT_ _ _ cuz he's ignorant of basic principles and needlessly rude to posters! For example he said when air and water are same temp that bird gets energy from disassociation of water:rolleyes: When any ordinary moron knows dTemp is just from evaporative cooling of wet fabric on beak! That's why I showed them it couldn't work when RH is too high or with novelties that expect water temp lower than air temp! HP I know you are open minded to some of Keely's ideas and all that but I also say Super Mods shouldn't ridicule newbies to push fringe ideas in favor of common sense! Anyhow I took the liberties of reinstating banned posters and putting lockout on Ryan's SM account until you sort it out:rolleyes: Sry cuz I know you're busy enough already:(
ALEPH!:mad: While I have no objection to your described 'actions' nor argument with your concerns -- It does not , by any stretch of logic, bear discussion here!!!!:mad::mad::mad::mad:

With jaded regards
HP:rolleyes:
 

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
Hence the 'bar' is rather low as it stands -- let's not make it subterranean!:rolleyes:
HP Ok I agree that's a good point:cool:!

No kidding?:rolleyes:
HP That's uncalled for:(! Cuz I wasn't criticizing just saying we're almost done:)!

It does not , by any stretch of logic, bear discussion here!!!!
HP, Ryan is a total jerk that you shouldn't be worrying about! Last year when you were on vacation and he explained your absence by saying you committed suicide and ppl believed it cuz of his position as SuperMod you said he was on _thin ice_ and now this! HP I say just cuz he mods for free is no excuse for willful bad conduct! I mean being shot in the back is free too but nobody thinks its ok cuz it's free:rolleyes:

HP I'm so sry my being on YOUR side angers you:rolleyes:!
 
HP I say just cuz he mods for free is no excuse for willful bad conduct!
No, not an excuse but... Let's put it this way - if you're willing to take it on yourself or wish to vouch for a personal acquaintance interested in the 'job' (complete, if desired, with compensation including benefits, etc...) -- then by all means show RT the 'door'!:cool: -- Get my point? --- I'd rather endure the known proclivities of a personal acquaintance ('gratis' or otherwise) than risk the vagaries of a 'web associate'! -- Agreed! RT is a lame practical joker (you will please pardon the redundancy:rolleyes:) and an aggressive proselytizer as regards his 'pet theories' - but such represents the extent of his 'errancy' which is more than could reasonably be assumed of a 'promoted member' or otherwise 'web-only' acquaintance --- But then you seem to have matters in hand, so what's the problem:confused:?

Regarding -- Can it be? The tutorial?! (remember that?) -- Here's the deal: I will be scarce the next few days during which I will endeavor to (incrementally) complete the tutorial (Post #625) -- Although time will not likely permit detailed annotation of progress nor response to posts, PMs etc... during said time, I will, however, 'update' the 'Last Action time' header (at the 'top' of said post) as appropriate. -- Please rest assured that I will view any posts or PMs taging/addressing me in the interum...

SO... If all goes as expected my next post to this site will be by way of announcing completion of the [pen]ultimate draft (i.e. the final draft pending proofing):):):)

All the best
HP:cool:
 
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