I can say with absolute certainty that @Jazz2C likes you! How do I know? Because he said so while comparing you to his father.

... and the plot thickens ... brb ... gona prepare my self a snack-sized bag of popcorn...

 

Shortbus wasn't it clear inductor is for LOPT test exciter and proper driver circuits? Cuz if not, OUR BAD!

It may have been to others, but not from my point of view. The discussion was about LOPT's and then was involved into pot cores. With no mention of a change of topic. How is someone like me that is interested but not involved to understand that the pot core isn't going to be used as the core in the LOPT coils that were previously removed? You(the main group) knew this wasn't the case but how was anyone else to know?

 

<<link to latest version of current tutorial>>

The discussion was about LOPT's and then was involved into pot cores. With no mention of a change of topic. How is someone like me that is interested but not involved to understand that the pot core isn't going to be used as the core in the LOPT coils that were previously removed? You(the main group) knew this wasn't the case but how was anyone else to know?

Shortbus that's a vry good point! I say we need to make better effort tying thread's on-topic content to tutorials Cuz even though non-linear thread is inevitable (cuz of simultaneous development on different parts of projects), incoherent thread is totally unacceptable! So entire issue will definitely be major topic of GTM right after HP's return!

So for now I'm requiring all subsequent posts by members of core development staff and alpha test team which have ANYTHING to do with engineering or technical aspects of projects to contain header descriptive of post's context!

So here's example header:

Re: Decoupling inductor for test exciter (Ref: part 3 of current tutorial)

~~~body of post here~~~


So anyhow we'll definitely find more elegant solution when HP is back but for now I say this can help prevent confusion

 

<<link to latest version of current tutorial>>

Important: So ppl have commented on my use of _FB_ and _FBT_ (_flyback_ and _flyback transformer_) and like that, my bad! So anyhow in narrow context I'm using, it's just reference to component from CRT tv, so totally synonyms with LOPT. So I promise to try and avoid that from now on!

Re: Circuit for LOPT test exciter (Ref: part 3 of current tutorial)

So @theodoravain and I have been receiving email asking abt exact circuit to use for testing LOPTs after modification. Which, BTW, if you ppl would just register with AAC you could PM us which we'd definitely see sooner cuz speaking for myself (and I'm pretty sure HP and TV also) I look on my public email accts like once a week max! Also since I've basically abandoned some addys, depending on where ur sending it, I might not even see your question! Now if you PM us with AAC's _start conversation_ feature we'll see _alert_ whenever we're logged in to AAC!

So anyhow abt circuit, it's not 100% decided yet mainly cuz compromise needs to be made between enough current availability for proper test but not enough to instantly ruin LOPT if arc strikes to/from HV winding. Also vry low current is important for safety cuz of totally casual test setup and also a lot of readers prolly aren't used to working with HV, YET! So short circuit output should be inherently limited to 500μA Max, but circuit needs to make abt 30kV under 200μA load (by which I mean 30kV peak drop across 150MΩ).

So just FYI test circuit will be vry close to Non-Resonant circuit shown in HP's post (which I attached here for easy reference) but plz it's only reference! Actual test circuit will be improved for reliability and safety to LOPT and builder!

Now since I have questions from ppl wanting to simulate non-res circuit in Ltspice all I can say is only thing I can suggest to make it accurately simulate is putting cap between collectors (so across winding formed by L1 and L2) which o/c turns it into resonant circuit with nice sine output so point is lost!

Just being clear non-resonant circuit works in real world! But actual output is somewhat like CD driven Fe induction coil (by which I mean narrow HV spikes separated by LV ringoff). So it's good for testing insulation integrity and like that but definitely not for proper driver!

Anyhow If U insist on playing with simulation you'll definitely need to provide ground path from L4 (which doesn't make circuit simulate properly but is necessary to run simulator cuz Spice doesn't like floating nodes.)

Here's something else u should know! LTspice can't simulate power oscillators accurately with _appropriate_ power transistor models! (problem applies to BJTs and MOSFETSs)! So for example with resonant version of BJT Royer of basic form shown below, 2N3773 is good real-world choice for active devices, but for accurate simulation it's best to just use Spice's generic NPN or small-signal device! Same thing for like Mazilli royer (ZVS), use large signal MOSFETs in real world but generic for simulation! So anyhow I'm total idiot abt Spice and I can totally say all four CDT members who regularly post on here (by who I mean HP, TV, JC and I) are basically _spice newbies_ so if someone more familiar with Ltspice has solution to simulation problems we'd be totally happy to hear from you! So all we ask is plz remember it's only solution if it doesn't require substantially redesigning circuit that works properly in real world!

So here's disclaimer: These tutorials and projects are definitely NOT meant as exercises using Spice! But since it's basically _keeping up with the times_ and a lot of ppl are raised on using simulation as basic tool to gain understanding and insight plus embarrassing fact that we (HP, TV, JC, A0 et al) could definitely benefit from Spice proficiency ourselves comments and discussions abt circuit simulation are definitely welcome! But to avoid digression, if discussions abt simulation problem get _deep_ we have to move on which can mean just moving discussion of Spice issue to another thread (which we'd hope to follow too!). Then when paradox is solved we'd all benefit w/o losing time on this thread with digression!

So also plz remember the ASC files for all circuits drafted in Ltspice editor are available on request!

Now this is for all you _finger wavers_ telling us u don't like non resonant circuit!
I KNOW circuit is crazy inefficient!
I KNOW output waveform is basically useless for anything except striking arcs!
I KNOW it won't practically work with cascade!
I KNOW mean output is like <10% of peak!
But I also know it's perfect for purpose we're proposing 2 use it for which is basically specialized Hipot testing!

So anyhow HP will definitely be back next week also Theo and I will have more free time the rest of May too! So we should definitely be back at it next week!

So here's copy of schematic of _generic_ non-resonant Royer oscillator from HP's post. Plz remember this is just to give basic idea of circuit operation! Definitely NOT circuit suggestion!

 

@HP and Co.

So our findings thus far:
As far as thermoplastics go, PTFE is the best choice from a strictly functional POV. After slight initial plastic deformation (approximately 7% at 670 kPa) it's purely elastic. What impresses me most is its unchanging properties over the test temperature range (0°C to 200°C). According to (monitored) inductance and saturation characteristics, the test pots' gaps were unaltered after 10 days continuous compression at 670kPa under a temperature of 200°C. When brought down to "cold soak" at 0°C the L shift was less then 5%! It is noteworthy that core material thermo-tracking predicts a similar change of over 3.5%. When the cores were dissembled for inspection, spacer thicknesses were practically identical to those recorded following a single, room-temp, compression cycle before the 10 day heated clamp test! I'm satisfied that, following prestressing, PTFE will not undergo further significant plastic deformation within (and well beyond) the planed operating temperatures and pressures. But, yeah! it's highly elastic! A non-thermoplastic bolt or @The Electrician's suggestion of a hard-setting, non-thermoplastic (perhaps phenolic based) adhesive should assure ideal long term performance. The main objection to PTFE remains machineability issues.

Compared to PTFE, Polyimides are more liable to plastic deformation but, in my opinion, sufficiently elastic to provide good results over the temperature and pressure range of our application.

I haven't yet obtained samples of Nylon-66, PETE, HDPE, or polyurethane "shim stock" (still working on it) Nylon-6, by the way, is a loser! But then I guess we all knew that.

@HP my advice (you asked). Try to find a non-thermoplastic solution! You know the drill! Mica, phenolic, pressed (non-hygroscopic) cellulose paper, celluloid..) If that's not an option then it's rigidly clamped PTFE all the way!

Well, yeah! The jury's still out on the shim materials, hoping for a jewel in the rough there! Off-label magic and all Be back when I have something more to report!

Thanks!

 

I've only been following this thread intermittently; most of it's way over my head, so I may have missed this but have you considered FEP or PFA. These plastics have similar properties to PTFE with some advantages.

 

<<link to latest version of current tutorial>>

Re: Discussion of gap spacer material for driver collector/drain 'chokes' -- general discussion...

I've only been following this thread intermittently; most of it's way over my head, so I may have missed this but have you considered FEP or PFA. These plastics have similar properties to PTFE with some advantages.

Many thanks for your interest and input!

To my knowledge our CDT's review of fluoropolymers included only PTFE, PVDF and ETFE (@Aleph(0) and/or @theodoravain please advise) --- That said, I seem to recall that while FEP and PFA exhibit significantly improved chemical stability within their working temperature ranges, said ranges are, unfortunately, rather disappointing (indeed, a quick glance at 'the web' shows maximum working temps of 204°C and 260°C respectively) as are said polymers' 'pan-thermal' strengths... FWIW A unique property (among thermoplastics) of PTFE is to be appreciated in its well neigh constant 'mechanical' properties (i.e. plasticity, elasticity, hardness, strength, etc...) over wide ranging temperatures (from -30°C to within 20°C of its MP [which being ≈ 330°C]).

Try to find a non-thermoplastic solution! You know the drill! Mica, phenolic, pressed (non-hygroscopic) cellulose paper, celluloid..)

Good deal! 'Tho I venture to ask where? -- Suitable mica forms are difficult to source, phenolic is prohibitively friable, cellulose fiber products are hygroscopic and chemically/'biologically' unstable by their nature (and, hence, require treatment with potentially 'dimensionally-destabilizing' sealants/preservatives, celluloid is both hygroscopic and chemically unstable, fiberglass panel products are little more than reenforced polyepoxide, amorphous and crystalline glasses (while otherwise excellent) are too brittle for commercial availability in 'gauges' much less than, perhaps, 1mm... -- But hey! I hear you! A substance exhibiting plastic, elastic and thermal characteristics on a par with those of the ferrite itself would solve many, many problems!

Kudoes, BTW, on your (tacit) recognition of the plain fact that celluloid is not a true thermoplastic despite its historical designation as same! -- Call me 'old-fashioned' - howbeit, in 'my book', if pyrolysis precedes significant 'softening' - it ain't a thermoplastic!

BTW, if you ppl would just register with AAC you could PM us which we'd definitely see sooner cuz speaking for myself (and I'm pretty sure HP and TV also) I look on my public email accts like once a week max! Also since I've basically abandoned some addys, depending on where ur sending it, I might not even see your question! Now if you PM us with AAC's _start conversation_ feature we'll see _alert_ whenever we're logged in to AAC!

Agreed!

TIHIDI? How many guesses do I get?

TIHIDI = This Is How I Did It --- Some projects (e.g. The Balanced EHT Indicator and the Unregulated Variable Low EMF Power Supply) while essential to this material are sufficiently 'basic' in scheme and requisite of acceptable components/construction technique so ubiquitous/varied that mere construction examples need be offered - thus affording the reader convenience and economy via use of 'parts on hand' (or otherwise readily available components) -- please rest assured, however, that --as always-- 'on-demand' elaboration/support goes without saying!

For the benefit of the curious (there are always a few) The blog entries (linked below) contain 54 images thusfar captured for use used in The Balanced EHT Indicator Mini-tutorial (TIHIDI)...
Entry A
Entry B
Entry C
Entry D
Entry E
Entry F

So since ppl reading for first time could easily have impression from title that this thread is extent of THE instructional material and so totally understandably make mad dash for horizon w/o backward glance, I have suggestion:

From now on plz link current version of Tutorial on top of all your posts to this thread (like I did on this one)

So for now I'm requiring all subsequent posts by members of core development staff and alpha test team which have ANYTHING to do with engineering or technical aspects of projects to contain header descriptive of post's context!

Excellent suggestions! --- Um... @theodoravain? Did you forget something on your last post?

In case anyone 'not in the know' gives a rat's a... Ahem... is interested -- I'm awaiting @Aleph(0)'s and @theodoravain's determination of a suitable gap spacer material - whence the 'LOPT rebuild tutorial' may finally be completed lo these three years!

In the meantime I'm 'working ahead' on the EHT indicator 'Mini-tutorial'...

Very best regards and many sincere thanks all around!
HP

PS @Aleph(0) --- I saw your email in regards to the 'urgency' of photos of the cores -- Please elaborate?

 

FWIW A unique property (among thermoplastics) of PTFE is to be appreciated in its well neigh constant 'mechanical' properties (i.e. plasticity, elasticity, hardness, strength, etc...) over wide ranging temperatures (from -30°C to within 20°C of its MP [which being ≈ 330°C]).

I still haven't got an answer to my question about the whole spacer problem, that I asked a while ago. That question was, why is the spacer which is buried in the core more susceptible to degradation form what ever is the worry, than either the nylon screw and nut holding it together or the magnet wire insulation made of either nylon or a version of polyester? Both of those things, the screw or insulation would be even more exposed than the spacer.

 

<<link to latest version of current tutorial>>

To my knowledge our CDT's review of fluoropolymers included only PTFE, PVDF and ETFE (@Aleph(0) and/or @theodoravain please advise)

HP Since u know Theo is totally handling materials testing IDK why ur tagging me abt that?

Some projects (e.g. The Balanced EHT Indicator and the Unregulated Variable Low EMF Power Supply) while essential to this material are sufficiently 'basic' in scheme and requisite of acceptable components/construction technique so ubiquitous/varied that mere construction examples need be offered

HP I'm vry happy u get that! It's rare case of function totally trumping form so giving detailed example with emphasis only on critical requirements is perfect!

Um... @theodoravain? Did you forget something on your last post?

HP tnx for saying that so now I don't have to!

I'm awaiting @Aleph(0)'s and @theodoravain's determination of a suitable gap spacer material

HP like I'm saying that's basically Theo's bid! So since ur asking my opinion I say PTFE isn't perfect but it's as good as it gets for material easily sourced in small qtys!

PS @Aleph(0) --- I saw your email in regards to the 'urgency' of photos of the cores -- Please elaborate?

HP I just mean what u call a _how supplied_ pic! So I know it sounds like unnecessary work but I don't have to tell you what that Charterhouse bunch is like! So anyhow since you wanted them in it, it's TOTALLY your call!

whence the 'LOPT rebuild tutorial' may finally be completed lo these three years!

HP sometimes I get sinking feeling it's like theme of retro tune

 

<<link to latest version of current tutorial>>

why is the spacer which is buried in the core more susceptible to degradation form what ever is the worry, than either the nylon screw and nut holding it together or the magnet wire insulation made of either nylon or a version of polyester? Both of those things, the screw or insulation would be even more exposed than the spacer.

Shortbus right now it's not so much concern abt problem of chemolysis and radiolysis as it is elastic and thermal property of bolt and spacer. So like @The Electrician and @theodoravain say is prolly better to secure core halves with hard high-temp glue. But for now we need core to be like _re-entrant_ to save readers time and money during development stage (so into _gama phase_). Now if ur asking why Nylon-6 works as fastener but fails as spacer all I can say is I don't totally understand that either So I say it's prolly that higher volume of fastener gives it enough _reserve elasticity_ to stay in tolerance but spacer's low volume makes properties totally more critical. Thinking on it I say shape (by which I mean elongated cylinder vs vry thin disk) prolly has more to do with it than volume.

So anyhow final choice will need good chemical (oxidizer) and ionizing radiation resistance too.

 

Glass filled PTFE then? There are many suppliers of the material in sheet, gasket and washer forms.

 

@ Aleph(0), I just know from practical use. Theoretical/data sheet things don't always hold true in real world use. I've seen plastic shim stock used in many parts of plastic molds and then reused again and again, without a change in size shape or thickness. Extrusion presses too.

 

<<link to latest version of current tutorial>>

so yes, there are materials out there that can easily outperform and outlast what's stated in their datasheets ... and the other way around. I.E., I had a hard time selecting an adequate material for a piece of string that I needed to submerge in FeCl3, and its datasheet said that nylon was an excellent material for that application ... and nope, it didn't perform as promised ...

My point is, datasheets are very good references and starting points to start experimenting with, but the only way to know for sure if something really works is to test, test, test...

@ Aleph(0), I just know from practical use. Theoretical/data sheet things don't always hold true in real world use. I've seen plastic shim stock used in many parts of plastic molds and then reused again and again, without a change in size shape or thickness. Extrusion presses too.

Kind, friends please rest assured we get it! It is for precisely that reason that Theo's team are testing and re-testing 'everything in sight'! Please don't let our oft-proclaimed aversion to 'empiricism' create the wrong impression! -- As anyone having 'tangled' with, for example, 'Spice' will attest (powerful, indispensable tool that it is) there's simply no substitute for 'real-world corroboration', as it were -- Thus it is with applicability of materials to specific, 'off-label', applications

FWIW (Re: gap-spacer material) @theodoravain claims to have found the solution with expression of intent to 'unveil' same (on this thread) at the weekend (why she cannot merely present her 'discovery' sans a 'press-conference style' 'side show' is beyond me). No need to ask! I too am 'in the dark' at this point

Glass filled PTFE then? There are many suppliers of the material in sheet, gasket and washer forms.

Excelent suggestion! Such would seem to offer the best of both worlds! @theodoravain please check this out! ('magic bullet' waiting in the wings or not)!

HP I just mean what u call a _how supplied_ pic!

Can do! -- Please look for my post tomorrow (Friday) evening!

I don't have to tell you what that Charterhouse bunch is like!

Indeed not!

So anyhow since you wanted them in it, it's TOTALLY your call!

Well hey! No need to blame me! As you might recall 'twas I and I alone who knew a Beyle from a Stendhal

Very best regards
HP

PS
Attn: @Aleph(0) --- Assuming @alephan is indeed TW - please encourage him out of lurk-dom! --- We need all the help we can get!

 

It is for precisely that reason that Theo's team are testing and re-testing 'everything in sight'!

That's the spirit!

Excellent suggestion! Such would seem to offer the best of both worlds!

Hey! ... I'm the one who suggested that in the first place! ...

 

<<link to latest version of current tutorial>>
In regards to gap spacer material


So seeing that my Leaseweb VPN (Zenmate if you care) is down to just two semi-functional locations and sinking fast, I suppose I'd better out with it in case and/or before the frost sets in.. (@Aleph(0), really! I'm certain we can do better than this? Perhaps a set of soup cans and some string?)

FWIW (Re: gap-spacer material) @theodoravain claims to have found the solution with expression of intent to 'unveil' same (on this thread) at the weekend (why she cannot merely present her 'discovery' sans a 'press-conference style' 'side show' is beyond me). No need to ask! I too am 'in the dark' at this point

Yeah, well.. No big secret really. It's that other "non true thermoplastic" polymer. Namely silicone (in the form of "thermal transfer matting", you know, the alternative to heat-sink paste). What's to like? Well first of all, like PTFE, plastic deformation is limited to a few percent of its virgin thickness, after that deformation is purely elastic (more so than PTFE). But here's the big deal! Our tests show it to be "elastically static" across and beyond the required temperature cycle range. As a for instance, clamped to 300kPa at 18°C, compression remains at 300kPa at -50°C, at +200°C and all points in between with no measurable variation in thickness. So yeah! That much can almost be said of PTFE but silicone maintains its properties better over a wider temperature range and, to the point, because of its huge elasticity there's no need of a wide variety of thicknesses. The required gap is achieved by clamping (elastically deforming) the spacer to the desired thickness using a permanent non-thermoplastic fastener or securing the shells with an appropriate adhesive prior to removal of a temporary bolt. Stock is commonly available in 500μm and 200μm (virgin) thicknesses. That covers the range of realistic gap lengths. For example our 250μm gap is established with a spacer cut from 500μm stock clamped to about 170kPa. @HP Do me a favor and up a pic of a blank "Thermo-Pad". I gather that you know where I stand on uploads from my phone? Too much metadata, too much BS!

Glass filled PTFE then? There are many suppliers of the material in sheet, gasket and washer forms.

Excelent suggestion! Such would seem to offer the best of both worlds! @theodoravain please check this out! ('magic bullet' waiting in the wings or not)!

Hey! ... I'm the one who suggested that in the first place! ...

On my word! We'll be checking it out, attribution aside!

I just know from practical use. Theoretical/data sheet things don't always hold true in real world use. I've seen plastic shim stock used in many parts of plastic molds and then reused again and again, without a change in size shape or thickness. Extrusion presses too.

Do you have a specific product suggestion for our test program (search committee?)? It looks like "Artus Inc." is a major supplier but their catalog covers a lot of ground..

I don't have to tell you what that Charterhouse bunch is like!

Well hey! No need to blame me! As you might recall 'twas I and I alone who knew a Beyle from a Stendhal

Thanks!

 

PS @Aleph(0) --- I saw your email in regards to the 'urgency' of photos of the cores -- Please elaborate?

HP I just mean what u call a _how supplied_ pic! So I know it sounds like unnecessary work but I don't have to tell you what that Charterhouse bunch is like!

Pictured below are a few trays of shells as supplied --- Note the 'heap' of Ca. 50 (similarly supplied) bobbins (immediately to the right of the US $20 bank note) -- Sorry! I'm not about to open a 'new' carton of bobbins for this, IMNSHO, pointless image!

Stats:
)36 shells per tray
)10 Trays per carton
)160 cartons per pallet (16 per tier * 10 tiers)
For a total of 57,600 shells = 28,800 complete cores per pallet (neglecting the bobbins). -- Yawn!

--Post continued below images--

Pictured below is an image of the product label (attached to each tray) as per the logo (and @The Electrician ) it seems the cores are indeed of 'Ferroxcube' manufacture

@HP Do me a favor and up a pic of a blank "Thermo-Pad".

Will do immediately I locate a 'specimen'! -- Those sheds were positively sweltering today and the outlook for tomorrow is worse still

(@Aleph(0), really! I'm certain we can do better than this? Perhaps a set of soup cans and some string?)

@Aleph(0) -- Not to kibitz howbeit it seems Theo has a point! You chose Zenmate, found its gratis servers less than satisfactory but then encouraged @Jazz2C and Theo's use of same? Thus I'm bound to ask -- is it a case 'projected masochism' or merely 'misery loves company'?

Very best regards
HP

 

is it a case 'projected masochism' or merely 'misery loves company'?

Maybe she believes in the third option: "purification through self-inflicted suffering" ...

 

<<link to latest version of current tutorial>>

IMNSHO, pointless image!

HP Sry but like I said YOU wanted Charterhouse ppl in it!

Pictured below are a few trays of shells as supplied --- Note the 'heap' of Ca. 50 (similarly supplied) bobbins (immediately to the right of the US $20 bank note)

HP for total clarity I say u should put pix of inductor assembly from post 1320 in blog (so guests can see them too) and link them down here near _how supplied_ pic! Cuz that way ppl can have like _big picture_

@HP Do me a favor and up a pic of a blank "Thermo-Pad".

Will do immediately I locate a 'specimen'!

HP They're with all your GC/NTE stock! I know cuz I saw them there last summer!

Those sheds were positively sweltering today and the outlook for tomorrow is worse still

HP plz get a life! You won't melt!

@Aleph(0) -- Not to kibitz howbeit it seems Theo has a point! You chose Zenmate, found its gratis servers less than satisfactory but then encouraged @Jazz2C and Theo's use of same? Thus I'm bound to ask -- is it a case 'projected masochism' or merely 'misery loves company'?

HP for the 1,000,000'th time! Registering paid acct (with any VPN not just Zenmate) means giving out name and banking info which totally defeats privacy! Also like you know pay-pal or debit card can limit damage from identity theft but doesn't actually help protect privacy from determined snoops at all!

So only other alternative I can think of is we all just connect to internet through your network but you say you don't want to _own our browsing habits_ and anyhow all having same IP and MAC addy would just encourage ppl saying we're puppets or commune or something So anyhow glitchy VPN is our problem no reason for you to keep complaining abt it

Maybe she believes in the third option: "purification through self-inflicted suffering" ...

Cmartinez it's true I sometimes wear _hairshirt_ too proudly But in this case I say it's just like _generation inversion_ by which I mean millennials (like Theo, JC and me) are more privacy conscious than Gen-X HP

Attn: @Aleph(0) --- Assuming @alephan is indeed TW - please encourage him out of lurk-dom! --- We need all the help we can get!

HP no was is Tony @alephan! Cuz just looking on his profile he joined like 11 years ago!

So anyhow major tnx for pix of core packaging!

 

<<link to latest version of current tutorial>>

Yeah, well.. No big secret really. It's that other "non true thermoplastic" polymer. Namely silicone (in the form of "thermal transfer matting", you know, the alternative to heat-sink paste). What's to like? Well first of all, like PTFE, plastic deformation is limited to a few percent of its virgin thickness, after that deformation is purely elastic (more so than PTFE). But here's the big deal! Our tests show it to be "elastically static" across and beyond the required temperature cycle range. As a for instance, clamped to 300kPa at 18°C, compression remains at 300kPa at -50°C, at +200°C and all points in between with no measurable variation in thickness. So yeah! That much can almost be said of PTFE but silicone maintains its properties better over a wider temperature range and, to the point, because of its huge elasticity there's no need of a wide variety of thicknesses. The required gap is achieved by clamping (elastically deforming) the spacer to the desired thickness using a permanent non-thermoplastic fastener or securing the shells with an appropriate adhesive prior to removal of a temporary bolt. Stock is commonly available in 500μm and 200μm (virgin) thicknesses. That covers the range of realistic gap lengths. For example our 250μm gap is established with a spacer cut from 500μm stock clamped to about 170kPa.

Theo I like it but I also say it just seems too good 2b true So all I'm saying is plz test SPECIFIC product brands so we can suggest with confidence!

 

<<link to latest version of current tutorial>>

Re: 'Zenmate'/Connection issues

So anyhow glitchy VPN is our problem no reason for you to keep complaining abt it

Because you and Theo (especially you) persist in belabouring the issue!
As an aside -- By way of a first-hand 'look-see' I've connected through Zenmate's gratis HK location most of the day and experienced zero difficulty! -- Fancy that?! Thou doth protest too much, methinks

Well hey! @Aleph(0) and @theodoravain -- In all sincerity I've no doubt whatever that the service is sporadic (that I merely 'caught it on a good day') -- but then ya get what ya pay for! -- Bottom line: I'll shut up about your wonky connections the very instant you do...K?

Re: Reluctance gap spacer material

@HP Do me a favor and up a pic of a blank "Thermo-Pad".

HP They're with all your GC/NTE stock! I know cuz I saw them there last summer!

Here 'tis -- Pictured is a 12"*12" square of 250μm stock (New Tone TP0012A) -- Please note that I have turned back the upper left-hand corner as an aid to perspective:

@theodoravain -- Two points:
1) The product is described as 'Fiberglass, Silicone Elastomer' (Emphasis added) -- Good?, Bad?, Non-issue???
2) I have been unable to locate a source for > 250μm stock? Although 'stacking' is an option I'd want to see some test stats as regards the viability of said scheme prior to recommendation of same...

--Post continued below image--

Re: Unregulated Low voltage power supply:

OVP(left) Zener transient suppressor:
Function: Preclusion of filter capacitor abuse corollary to EMF up-swings during near maximum output EMF operation.

HP I have better idea! Why not just use filter caps with working voltage rating above maximum open circuit output?

It has long been my observation that 'non-solid electrolytics' featuring nominal capacitances much greater than 20 millifarads must needs frequently approach their maximum working EMF is dielectric integrity to be maintained...

Having reflected upon Aleph's well considered suggestion --and my pathetic expedient/rationale (emphasized above) I know I can do better

Following significant (non-original) research and consultation with several manufacturers - it seems 15 millifarad @250V electrolytics will be wholly acceptable in this application --
That said, I nonetheless strongly advise allowing the caps to 'soak' at Ca. 85V-100V (i.e. max PSU OC output) occasionally...

Example of acceptable capacitors -- inexpensively purchased new or readily salvageable (in good condition) from multi-killowatt power conversion systems (e.g. inverters/UPSs).

Best regards
HP