EHT power supply design and construction

Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
Edit Feb 20 2018

To all concerned: As a result of _content management_ most internal and external links to posts on this thread are currently misaddressed. Your patience is greatly appreciated pending our resolution of this issue:cool:.

The current version of tutorial starts HERE:)! Tnx!


Edited for formality by Aleph(0) 2/20/18

Fwiw here's original post 1 below:)
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I want to take core from old tv doughnut wound flybacks without damage the winding but they usually break!:( Does anyone know the ways to this?:D
 
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#12

Joined Nov 30, 2010
18,217
I don't think that is possible. After the winding is finished it is dipped in something like varnish. Maybe if you could dissolve the material you could get the wire, but it would also be stripped of insulation.

Transformer manufacturers do not make any accommodation for disassembling their products. (This is part of my job history.)
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
@Aleph(0)

If the 'transformers' in question are of the 'modern' style I tend to agree with @#12 -- You can have one of the core OR, possibly, the 'potted coil assembly' -- both, however, would be a neat trick indeed...

Inasmuch as you described the device as 'doughnut wound' I'll assume you were indeed referring to the 'old style' LOPTs

Yes, with a lot of patience your aims are attainable...

The 'key' lies in the fact that these units are assembled with polyepoxide based adhesive -- which being readily 'softened' via moderate heating...
Said heating is most readily accomplished inductively (~50 KHz being optimal in my experience) --- Make certain, however, to shunt the secondary (i.e. the EHT winding) thus protecting same from damaging EMFs and, at the same time, enhancing core heating...

Note: contrary to common belief, said 'shorting' of the EHT winding will not (directly) result in significant winding temperature rise! -- In point of fact, carried to extremes, thermal 'reflux' from the core will damage the winding long before resistive heating of the conductor itself reaches deleterious levels)...

Alternatively, you could use a 'heat gun' however such is not recommended...

Whichever method you choose take care to limit the temperature to 250° C -- Greater temps risk damage to the winding and permanent shift of the ferrite's magnetic properties...

So... The procedure:

1) Remove all 'hardware' from the form...

2) Using a scalpel, X-acto knife or similar tool, cut the 'signal'/EHT rectifier filament windings and associated bobbin off the lower 'end' of the form -- then carefully scrape away excess epoxy, etc...

3) Heat the core to approx 250°C --- Then, if using the 'induction method', disconnect the driver...

4) Apply strong, steady and absolutely linear traction to each core piece lateral to the bonds... --- Take great care that moments are not introduced by the inevitable unequal yealding of the bonds!!!

5) Once separated and removed from the EHT winding, the core pieces may be cleaned of residual epoxy via ketone solvents (e.g. acetone) --- take care not to lose the 'handy' 'air-gap' spacers...

Don't despair should you happen to break the core -- 'clean' breaks require nothing more than a bit of high-temp epoxy and 'creative clamping' to put them right (with the addition of an insignificant 'integral air-gap'):)

For your edification/encouragement I have attached the following images: the first image shows a disassembled LOPT of the type discussed --- in the second image is a similar device having been dissembled, then rebuilt for continuous 50KV operation

Here is a disassembled transformer of the type discussed... --- (US $0.25 piece included for perspective)
Dissa_LOPT.JPG

Here is a similar transformer having been first disassembled then 'rebuilt' for continuous 50KV 'open air' operation --- In case you're interested: Inadequate 'winding-to-world' insulation limits 'stock' transformers of this vintage to ~25KV (above which, corona and/or lateral 'strikes' rapidly 'ring down the curtain') although the inter-turn insulation is 'good' to Ca. 75KV -- as evinced by trouble free, continuous operation at such potentials while immersed in dielectric oil (sans provision for admission of same to the inter-turn spaces)...
RePurpLOPT.JPG
 
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Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
Hi Ms. HP
I wind for royer circuit and run voltage at 40 for 10min! High volts wdg not for arcing becauce hold to 4000v by strobe tube so could verify working order. Had to do a duty cycle to save bipolar transistors but core just heated nice anyway :) Managed pull three apart and only broke two! Now I see that the moments means torques sorry because of languge barrer :( I think wonderful so thanks since you said not the likes;) Please tell me more about repair broken ferrite pieces? Also would you say 6bk4 or 2x2 best for x-light lamp?
I'm very happy now but I would like know why you delete my posts? escape from topic?
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
but I would like know why you delete my posts?
You seem to be under some misapprehension, I did not delete your post! Inasmuch as I have no moderator privileges here, the only scenario wherein I could (legitimately) delete another's post is deletion of my own thread upon which said post resides -- Come to that, I’m by no manner of being certain that threads are (standard-user) TS deletable following contributions by others -- That said I received both an alert and a PM from a member of the moderation staff advising me that one of my posts had been deleted for its mootness (my fault) following deletion your off topic post --- It would behoove you to bear in mind, as regards etiquette, that off topic posting/’thread-jacking’ is to textual communication as third-party interruption is to aural communication -- to wit: STRAIGHT UP RUDE!:mad::rolleyes:

But to move on:cool:

Managed pull three apart and only broke two!
I shall assume (based upon your use of the adverb 'only' and the 'happy' emoticon) that you successfully disassembled three of five transformers...

Hence;
"Should Sixty Percent Appear Too Small, Be Thankful You Didn't Break Them All...":p:p:p

Actually that's not a bad 'first round'!:)

Please tell me more about repair broken ferrite pieces?
So long as they're not 'shattered' there should be little difficulty - The 'devil', as they say, is in the 'clamping' --- Images of the broken forms would be helpful:)

Also would you say 6bk4 or 2x2 best for x-light lamp?
The 2X2 is -- far and away -- the best choice! BTW don't concern yourself with 'nation of origin' just observe the anode 'skirt' --- the best x-ray generators will have a sharp (as opposed to rolled) 'hem' - favorability of said geometry owing to the greatly enhanced field emission attendant thereto... It goes without saying that best all around results require 'cold', inverse-polarity operation (the filament makes a superior anode owing to its size, density and characteristic spectra).

Be advised that standard GM counters and ion chambers will be of little use below 45 kVp (~36 keV ~ 0.034 nm) --- the good news is the ubiquity of mammography 'enhancer' cassettes (check Ebay) thus equipped one may either monitor the output via 'fluoroscopic' effects or, with a PMT, construct a scintillation detector implementing the 'Mammo screen' as the 'crystal' :):):)

*Very* pleased to meet another 'Rader' (Grayer?;)):):):)

Best regards and good luck!
HP:D

PS --- Please take care!!!, too many "Clarence M. Dallys" and 'Big Bro' will be handing us the 'guff' he's now serving the LASER enthusiasts:(:(:(
 
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Hypatia's Protege

Joined Mar 1, 2015
3,226
@Aleph(0)

You probably already realize this - however I feel compelled to advise you that the above described cold cathode arrangement will not exhibit the 'self rectifying' behavior characteristic of Coolidge inserts --- This is doubly so as the 'ion current' will rapidly heat the filament which must serve as the anode! Thus application of AC will result in thermionic emission, forward rectification and subsequent overload of the EHT supply! -- To say nothing of 'focal spot' and 'target' material issues...

My advice is that you operate a pair of transformers each with its own (resonant Royer) driver and each followed by a full-wave doubler --- such an arrangement will safely provide up to 80KV at 6 mA (480W) for at least 30 seconds per 15 minutes (assuming open-air convection cooled operation)...

Below are links to a 'hobbyist friendly' HV component vendor:)

Here are the diodes / 30kV, 20ma, 100ns -- use of two series connected devices each leg of each doubler will grant a 33% safety margin at the maximum per-transformer EMF of 20KV Peak (i.e. 40KV p-p)
Note: owing to rectifier construction, equalization will not be necessary:)

http://www.amazing1.com/products/high-voltage-rectifier-30kv-20ma.html

And the caps:
Look for model '80KVDKT' under: "Super High Voltage N4700 Ceramic Capacitors" / 1nF @ 80KV (3.2J)--- No need to 'balk' at the price! You only require four of them!:)

http://www.amazing1.com/capacitors.html

Hope to have been of help!
Best regards
HP
 
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Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
Right I salvage three intact from the five:) taxman? heh! Also I am saying all your time for just me is lovely:D
Pls explain more how 2x2 should be for best use? You say skirt but I think bell? Is that same for structure of the intended to be anode? I understand about CC operating and low energy deaf survey meter:D Dont worry about my death from the ionizing rays like poor Clarance Daily! I understand about radiologic safety! Maybe die from shock instead! Ha! tnx for saying where to buy parts! your right! Not very expensive when I have all there I need for I say 1,000:D I ask where to buy resonance capacitor for royer driver? Will be pp? sorry to blame to you for my posts!:(
 
Right I salvage three intact from the five:)
Again, very good for 'early days':) --- If you need assistance repairing the broken forms please post an image of same --- FWIW: Adequate clamping is generally achievable via elastic bands...

I understand about CC operating and low energy deaf survey meter:D Dont worry about my death from the ionizing rays like poor Clarance Daily! I understand about radiologic safety
Pleased to hear it! -- Even so - beware complacency; The Great Destroyer! I tend to be (perhaps overly) sensitive on this subject owing to the sad fact that avocations involving hazardous 'agents' (CIP ionizing radiation) are especially 'vulnerable' to ignorant legislators and the public hysteria to which they 'dance' --- especially where said pursuits enjoy only a scant following... Your 'quip' (Re: electrocution) is well 'placed' inasmuch as electricity is, arguably, far more dangerous than X-Rays - in that, as regards the latter, undo [unprotected] proximity to the source represents the sole 'avenue' of peril ('cumulativity' notwithstanding) -- electrical hazards, on the other hand, are significantly complicated by the ubiquitous nature of same...
Additionally, it should be noted that, unlike radioisotopes/radionuclides, X-Ray use carries no contamination hazard (and, yes! I am quite aware of the phenomenon of radio-phosphorescence - so let's have none of that!;))

tnx for saying where to buy parts! your right! Not very expensive when I have all there I need for I say 1,000
Am I glad to 'hear' you say that!!!:D:D:D -- Following your 'whinging' Re: the modest cost of a new YU-181, I was given to question your alacrity (Re: upgrading the AL-1200) --- Point being; I am now 'reassured' as to your earnestness as regards your present endeavor...:)

You say skirt but I think bell? Is that same for structure of the intended to be anode?
Correct! - The structure connected to/extending from) the 'anode cap' ------ "Threads", "Ironmongery", whatever... We seem to be communicating!:cool:


Pls explain more how 2x2 should be for best use?
A sharp 'edge' is desirable inasmuch as it 'concentrates' the field (and, hence, enhances field emission) - an important consideration in cold cathode operation -- if that doesn't make much sense, I beg you recall that said electrode will serve as the cathode in this application!:)

I include the following images as an aid to anode geometry recognition:

Note: For whatever reason I find proper display of attached images often requires following the 'show in original location' link (penultimate upper right) on the attachment viewer window...

Here is the desirable configuration -- Notice the sharp 'hem' (or, 'flare' if you prefer the 'bell' analogy)...
NAT2x2a.JPG


Here is an example of a tube featuring a 'turned hem' --- While such construction improves the tube in its designed application, it is unfavorable for X-Ray production...
GE2x2a.JPG

Also I am saying all your time for just me is lovely:D
No problem! -- Always happy to encourage another in my obsessi... Um... hobby!;) --- Please be advised, however, that there are many members here, many of whom are far smarter than I!:) --- 'Diversification of company' could be rewarding!:D

Best regards
HP
 
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Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
My 2x2 anode like the turned up hem:( Can they work at all? Also have ion chamber plate for adjust collimator, will sensitive to rays from less than 45kvp on tube? I find enhancer cassette with code on screen says "min-r 2000 screen 0007007242ys9740" is that right the soft rays? thank you for cares:D
 
My 2x2 anode like the turned up hem:( Can they work at all?
Absolutely! In fact they'll give better performance than any 'flavor' of 6BK4:) --- FWIW tubes of 'optimal' design will generally be of Russian manufacture or old "National Electronics" stock...

I find enhancer cassette with code on screen says "min-r 2000 screen 0007007242ys9740" is that right the soft rays?
You've done well! The cited cassette is indeed a mammography (and, hence, low-energy sensitive) 'intensifier' It'll give a 'perty' blue glow when irradiated:):D

Also have ion chamber plate for adjust collimator, will sensitive to rays from less than 45kvp on tube?
Do you mean a spot-field chamber (such as pictured below)
TrexIC.JPG

Such instruments are generally spec'ed at 100kVp (i.e. ~80keV) their Al construction significantly attenuates energies below 60kVp -- That said it's worth a try -- you'll need to 'max-out' the Master/Field gain adjustment{s}...

The following image is offered as an example of a typical pin-out:

TrexICMan.JPG

Of course it goes without saying that unless you have the exact model shown (BTX161 with Pre-Amp board: 61122B) you'll need to do some research (Given numbers/manufacturer of your instrument I may be of some assistance)...
Note: Development of chamber 'bias' is best realized via a 'boost converter' or similar topology --current limiting to < 100uA will minimize damage in the event of failure or >YIKES< connector 'miscongress'

Even if the chamber proves unuseful at low energies Please hold on to it! -- You be glad you did once having 'graduated' to higher energy work!:):D

Best regards and good luck!
HP:)
 
@Aleph(0) -- Re: your Siemens AEC SFIC --- lacking, as I do, the faculty of clairvoyance, I'll need the specific model number if I'm to be of much assistance! - Moreover please just post here or PM me at this site! -- The 'email chase' is both burdensome and redundant!

With genuine respect
HP:)
 
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Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
How I find number for AEC? Cant read from firmware if connection no real rs232 port? How much HV you say if 2x2 submerged in the oil, like 80kv? I want just talk on PM conversations but you say not the chit chat:( is it my breath?;) pls be kind! I'm not dumb as I sound:(
 
How I find number for AEC? Cant read from firmware if connection no real rs232 port?
Would you believe - read it off a label with your 'pre-installed' organic 'imaging' faculties?:D

How much HV you say if 2x2 submerged in the oil, like 80kv?
While immersion in uncontaminated dielectric oil would certainly preclude external flash-over at that potential -- the tube itself might fail -- Please recall that cold-cathode operation relies upon an 'imperfect' vacuum -- So... 'Tis a case of not having it both ways... That said, If you have a few spares -- give it a try!:)

I want just talk on PM conversations but you say not the chit chat:( is it my breath?;)
Idle socialization is inconsistent with my aims here - which being (bidirectional) exchange of (pertinent) knowledge/information --- No need to take said stance personally...

pls be kind! I'm not dumb as I sound:(
No worries, my friend! --- Of the many epithets applicable to you, 'dumb' is conspicuously absent! --- To put a finer point on it: You're doing an exquisite job of sounding like a genius trying to sound like an idiot!:D:D:D


Best regards and continued good luck with your project{s}
HP:)
 
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Thread Starter

Aleph(0)

Joined Mar 14, 2015
597
No numbers to see until arrives from courier with preinstalled eyes of mine ha ha:D I having troubles with arcing from fb secondary wdg of which coaxial with EHT maybe need oil potting? Why you say that I am the genius because I write the bad english? I like but not understand why? Are you same Daniella N that made the texts to usenet sci forums but called yourself after Sister Hellen actress last name? Please say how to fix flyback no fun for only 15kv:(
 
I having troubles with arcing from fb secondary wdg of which coaxial with EHT maybe need oil potting?
The best approach is removal of the subsidiary winding and its associated (transfixing) cylinder followed by 're-mounting' of the EHT tyre, as it were...

FYI: The lug carrying the horizontal sweep amplifier's anode lead likewise carries two leads from the windings, one being the 'cold' end of the EHT winding and the other, the 'top' of the subsidiary winding (which being connected to all other taps) -- the process involves separation of the EHT return, 'evisceration' and removal of the subsidiary winding assembly and construction of a 'hub' fashioned of polypropylene and CPVC sleeves and electronics grade silicone adhesive.

Should you desire a 'step by step' I'll gladly oblige but please be sincere! --- Immersion in dielectric oil is problematic inasmuch as oil contamination and bunting material degradation will likely occur --- A 'quick and dirty' workaround merely disconnects the EHT return from the subsidiary winding then isolates same with petroleum 'wax'... Such an arrangement should allow upwards of 20KV (sufficient for the proposed dual transformer implementation) -- Be warned, however, that even moderate heating will melt the 'wax' resulting in failure --- While a similar expedient may, of course, be had with adhesives possessed of more acceptable thermal properties -- such is inadvisable for complications attending the essentially permanent nature of said applications...

Below are images of a fully reconstructed transformer... As with the transformer shown in post #4 this is now 'good' to 50kV+ --- Details upon request...

garret_Lab3a.JPG

garret_Lab3b.JPG

No numbers to see until arrives from courier
As I said, no pressure intended! Just wanted you to know that I may not be able to get the info prior to early Aug...

Are you same Daniella N that made the texts to usenet sci forums
It's your fantasy! You tell me...:D

but called yourself after Sister Hellen actress last name?
Say what?! -- I don't know whether to suggest a translator or a detox center!:confused::confused::eek:

Why you say that I am the genius because I write the bad english?
Because you are not an idiot you know the answer to that question!;););)

Also you never say where to buy the resonance cap?
http://www.mouser.com/ProductDetail/WIMA/MKP1O133306F00KYSD/?qs=sGAEpiMZZMv1cc3ydrPrFyY4BahsFf0/Qzy2qHcK3r8= :)

Do yourself a favor and buy several of them!:cool:

Best regards
HP

PS I apologize for cursory nature of this post:rolleyes: -- Know also that I am absolutely sincere in my offer of further details upon request:):D
 
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