Capacitor info required, any help would be appreciated.

[Old Croc]

Hi all,
I have an old CIG Transtig 180 welder and a capacitor in the High Frequency Pilot Arc box has failed. They are not available from the makers (Miller USA) or repairers of these 35 odd year old machines, and I have had no luck sourcing one via the net. As best as I can work out it is a 5000V AC .002micro farad. It is just a large block of plastic with 2 studs for terminals. On the net there are all sorts listed, but I do not know if any of them are suitable. Does anyone know of a suitable replacment, or what others could be combined to do the job. It will be a crying shame to have to dump this otherwise perfectly good machine and buy another chinese import.
Here is hoping someone can help,
regards,
Crocy.

[RayG]

Hi Crocy,

Any chance of a picture showing the markings and a picture might help narrow down the package type.

Here's a 0.002uF 6KV, does it look like this one?

S202M75Z5UU83L0R Vishay BC Components | 1269PH-ND | DigiKey (http://www.digikey.com.au/product-detail/en/S202M75Z5UU83L0R/1269PH-ND/2356805)

If that part was all you needed, I order stuff from Digikey every week, so I can tack it onto the next order, otherwise you'll get caught up on minimum order size.

Regards
Ray

[RayG]

Hi Crocy,

Can identify which part you are chasing in one of the attached manuals

http://www.woodworkforums.com/attachments/f160/214324d1341219756-transtig-180-ac-dc-welder-transtig-180-ac-dc-hf-700005-.pdf

http://www.woodworkforums.com/attachments/f160/214325d1341219756-transtig-180-ac-dc-welder-transtig-180ac_dc-operating-manual.pdf


If it's the one I'm thinking of, then it will be a paper film foil type like this series http://www.cde.com/catalogs/T.pdf


Regards
Ray

[Vernonv]

Ray,
The HF cap (with the studs) is part 10 on page 10. I have a similar vintage TransTig 250 and the cap in mine is similar/the same as the 180. Here is a pic of the cap from the 250 manual.
258390

[Vernonv]

Here is the circuit. It's 1C - 0.002uF 3kV.

258391

[RayG]

Hi Vernon,

From the look of it, that's a paper oil capacitor, so you'd be looking for 0.002uF , or 2nF or 2000pF 3Kv or better paper/oil, I'd expect a 2.2nF would work just as well.

I'll go see what I can find.

Regards
Ray

[Vernonv]

I thought I could read "mica" on the capacitor in the 250 manual. The slight change of capacitor value would only marginally effect the frequency of the circuit, which I would image isn't terribly critical.

[RayG]

Hi Vernon,

Just looking at the picture it looks like 0.002 MF, does that possibly mean it's 0.002 milliFarad, which would make it 2 uF Edit: see next post.

If that's correct then maybe something like this would do?

KBG-P 4KV 2uF RUSSIAN MILITARY HIGH VOLTAGE CAPACITOR | eBay (http://www.ebay.com.au/itm/KBG-P-4KV-2uF-RUSSIAN-MILITARY-HIGH-VOLTAGE-CAPACITOR-/251005615094?pt=LH_DefaultDomain_0&hash=item3a7119bbf6&_uhb=1#ht_789wt_1399)

Or http://www.cde.com/catalogs/HV.pdf Part number would be HVDMAS2J491B for 2uF 3Kv

Regards
Ray

[RayG]

Hi Vernon, Crocy

I've changed my mind, the one you want is this.

Capacitor 002 uf 5KV Transmitting Mica Ham Radio Tesla Coil | eBay (http://www.ebay.com/itm/Capacitor-002-uF-5KV-Transmitting-MICA-Ham-Radio-TESLA-Coil-/261187111735?pt=LH_DefaultDomain_0&hash=item3ccff70b37)


0.002 uF 5Kv Mica

Regards
Ray

[Stustoys]

Capacitor 002 uf 5KV Transmitting Mica Ham Radio Tesla Coil | eBay (http://www.ebay.com/itm/Capacitor-002-uF-5KV-Transmitting-MICA-Ham-Radio-TESLA-Coil-/261187111735?pt=LH_DefaultDomain_0&hash=item3ccff70b37)

That sure looks like the ones I have seen.
One tip, you want to keep the top of the cap clean enough dusts and you get an arch across the terminals that eats the top of the cap away.
At least thats thats the story the engineers came up with to explain the deep groove between the terminals.

Stuart

[Bob Willson]

I would send them an email querying that delivery price. They will probably repack it in a bag and send it a lot cheaper than that.

[Old Croc]

Ray, Vernon, Stuart and Bob. Thanks for all your help with this.:2tsup: Lost the hard drive again:o (when will Cliffie come back to Townsville) so have been offline, went to the internet cafe, but could not remember my password so could not reply. I decided to ask a guy at the Uni for help, and he recognised it as a Tesla coil circuit, rather primitive he said, but easy to fix and otherwise reliable. He took me on some searches of Tesla coil sites, and they explain what is required of the capacitor and he steered me to a site called (cant insert link) Information Unlimited, section, Tesla Accessories & Books, Page 3 and 4, where there are numerous purpose built capacitors for this application. I will try and get the one you found, but if not I will get one of these. Trying to decide if I should join all the welding forums, and let them all know as well, as there are a lot of these machines out there.
Any way, thanks again guys,
regards,
Crocy.

[mike48]

Hi

try also to get a capacitor of similar size with screw terminals.

This allows easy reconnection and insulation of existing cables etc in a (moderately) high voltage situation.

That eBay block type is what you need.
The cap value can be +/- 30%, but keep to the voltage rating or higher.

The suggested ceramic and other types will work, but it is the practical connection things which will make replacement easy for you.

You will most likely find that an old block mica type is best, and available, as millions were made, and they are stable with old age, and normally don't go leaky in the smaller values. Here is a case where age is not a problem.

If you cannot find a suitable capacitor, come back and tell us. Someone here will have one somewhere in their junkbox.

cheerio, mike

[Old Croc]

Thanks for the answer Mike, I have had feelers out everywhere when I read what the others had replied, but I will buy the 1 on ebay, as I am getting desperate to get the machine going again, to do some repairs on my mates Dragster. It must be my lucky day, as the repairer just rang, and my Plasma cutter is going again, so I can at least start cutting all the ally plate up ready.
thanks and regards,
Crocy

[mike48]

Hi Crocy

sounds good.
When you get it, wipe the cap down with metho, especially on the top between the terminals. While you are in there, also wipe all the high voltage cables and stuff with metho on a rag. or metho on a small paint brush, and let it all dry (sparks + metho = trouble).

Don't spray it with anything.
These things are not polarised.
Sangamo made high quality stuff, but if it is suspect it is leaky, you can test it with a megger or electrician's type electrical resistance checker at 1000V test.

After it is installed, and with the welder casing off, always assume that it is live, even when turned off, and always short the terminals out every time before working around it. A residual HV charge probably wont kill you, but may catch you by surprise, and you then might fall off a chair and hurt yourself.

I am curious as to how you determined that this capacitor was at fault and not the other components?

Now that you have tweaked our interest, tell us how the project goes please.

I somehow doubt if that type of welder would now get an "E Tick".
Are there any capacitors or filter on the mains entry?

Good luck,

cheerio, mike

[Old Croc]

Hi Crocy

After it is installed, and with the welder casing off, always assume that it is live, even when turned off, and always short the terminals out every time before working around it. A residual HV charge probably wont kill you, but may catch you by surprise, and you then might fall off a chair and hurt yourself.

I am curious as to how you determined that this capacitor was at fault and not the other components?

Now that you have tweaked our interest, tell us how the project goes please.

I somehow doubt if that type of welder would now get an "E Tick".
Are there any capacitors or filter on the mains entry?

Good luck,

cheerio, mike
Thanks for your help Mike. I am an electrician, but specialise in HV power systems, not electronics. After the other guy identified it was a tesla coil unit, I dug out an old text book from 40 odd years ago, to refresh my memory, and with the cover off, there was arcing at the spark gaps. There are splits and carbonisation in this HV capacitor, so I took a guess. Did a resistance and insulation test on the final step up transformer and it was OK. So now I wait for delivery. Will post the results,
rgds,
Crocy.

[mike48]

Hi Crocy

one of my favourite old books is "Electrical Engineers Reference Book" by MG Say.
Very useful.
I keep a hardback copy in old fashioned paper form, whereas I have given away a lot of my old collection.

If you need an interim repair, try three Jarcar RS5380 0.01MFD 3KV ceramic caps in series, and jury rig it with BPs and cable ties etc.

cheerio, mike

[Old Croc]

Hi Crocy

one of my favourite old books is "Electrical Engineers Reference Book" by MG Say.
Very useful.
I keep a hardback copy in old fashioned paper form, whereas I have given away a lot of my old collection.

If you need an interim repair, try three Jarcar RS5380 0.01MFD 3KV ceramic caps in series, and jury rig it with BPs and cable ties etc.

cheerio, mike

Well Mike, the Ebay capacitor finally turned up, but was stuffed, so $20 wasted, but worth a shot. I cannot find the capacitors you listed, are they from Jaycar or the RS catalogue? Will the caps you mentioned take the high current this set up needs?
In the meantime, I have found a guy in the US that has a lot of tesla gear online, and he has given me some options to pursue. I also spoke to Steven?, I think, at Token Tools and he was also very helpful, would probably buy one of his welders, but the waranty could be a problem from way up here, but not insurmountable. He also may have an option of supplying a retrofit HF from one of his machines, and if I can convince SHMBO to make a quick run to Sydney in June, I will drop in to his factory and have a look at it.
Thanks and regards,
Crocy.

[Bob Willson]

That is because there is a small error in the part number. Try this instead (http://www.jaycar.com.au/productView.asp?ID=RC5380&form=CAT2&SUBCATID=967#1) Part number RC5380

[Malibu]

one of my favourite old books is "Electrical Engineers Reference Book" by MG Say.
Very useful.
I keep a hardback copy in old fashioned paper form, whereas I have given away a lot of my old collection.


I'm with you on this one Mike... My two favorite books are "Principles and practice of electrical engineering" by Alexander Gray (published 1917) and a later one "Electrical engineer reference book" which may be the one you refer to, by Molloy, Say & Walker from 1948.
Some of the best information, and all still relevent, out of those two books.

[Old Croc]

Mike and Bob, thanks again for your input, but those little caps will not take the amount of current that moves in the HF circuit, hence why the correct one costs $500+, Just waiting for the guy in the US to answer some of my questions and if his alternate doorknob? ones will do the job, I will try his way first,
regards,
Crocy

[mike48]

Hi Crocy

oh dear - two errors in one line; must have been a bad day for me.
Apologies.

My suggestion should have read (as Bob correctly indicated) -
"try three Jaycar RC5380 0.01MFD 3KV ceramic caps in series".

I would have thought that it would work, as the caps are "low K type ceramic", and capable of some RF current.
What happened?
Did it work at all?

Anyway, I went through my junk box, and the only thing I could find is a French Steafix brand (good quality) 0.0026 MFD, 12 KV block cap with 8mm ISO coarse threaded lug connectors.
It is round, 60mm dia and 90mm long, and weighs 600grm.
I think it is mica, but there is a small chance it may be polyester.
I have tested it for capacitance, and for leakage and DC breakdown at 750V DC.
All OK.

You are welcome to this, at no charge.
Send me a PM for address or phone number etc.

Don't do anything drastic like buying a new welder yet.
I will also ask some of my mates for a block mica cap for you, similar to the original.

This particular capacitor came out of the transmitter section of a French manufactured Air Traffic Control type ground surveillance pulse radar, rated at 2 MW power at L band. That's not milliwatts, but megawatts.
I used to work on these very radars, and then taught pulse radar systems.

cheerio, mike

[Old Croc]

Thanks Mike, :2tsup: PM sent,
rgds,
Crocy.

[mike48]

Hi Crocy

PM reply sent with address.

The .0026 Steafix (type 433) cap holds it charge OK and a leakage test at 750 V DC has less than 0.1 microamp leakage, which should be OK. (It used to have a normal working voltage of 11 KV DC pulsed at 1kHz).
I have not got anything which tests at a higher voltage unfortunately.

However, as it possibly is mylar or polyester, it also may just not like continuous high RF current. No matter, worth a try.

I cannot find an old Steafix catalog to see what this exact type of capacitor is made from.

So, I will still attempt to see if my friends have a block mica, which normally have a rating stamped on them for RF current.

It is normally just a matter of temperature rise due to internal RF resistance, which is hard to see let alone measure at HF.
Mica is very good in this regard, and can handle RF well.
However "low K" ceramic types are OK also, and I was a bit surprised that your trial of the three ceramic caps "popped" off.
I can only assume from that failure that the Jaycar caps were "high K" (an RF parameter of the ceramic dielectric) types, which are lossy at RF.
So called ceramic "doorknob" types are normally good for HF RF but the only ones that I have in my junk box are 470pfd, or .00047mfd, and you would need four in parallel.

Anyway, try out the Steafix .0026 mfd, and see how it goes, while I search.

You know, years ago, we used to dump wheelbarrows of old HV mica capacitors like you need. There just wasn't any more need for them as transmitters changed from valves with high voltage, to transistors with lower voltage and ferrite transformer coupling.
I used to have some really large ones in my office as curiosities to impress visitors.
They were 400 mm high, with cylindrical white ceramic bodies and large metal end caps, and came out of 5kW MF/HF transmitters and antenna couplers.

cheerio, mike

[mike48]

Hi Crocy

as per PM, one 0.0026 mfd 12 kV capacitor posted off Friday.

Let us all know if it works please.

It is still worth looking for a known mica unit, with an actual RF rated current, but at a reasonable price, ie less than $20 plus post.

Good luck!!

cheerio, mike

[Old Croc]

Hi Crocy

as per PM, one 0.0026 mfd 12 kV capacitor posted off Friday.

Let us all know if it works please.

cheerio, mike

Just to let you all know, Mike kindly gave me a capacitor,:2tsup: and I hotwired it into the machine as a trial, and hey presto we have a pilot arc again. Because it is larger and the two on their way from the US are huge, I will have to get some copper cored spark plug wire from the local drag racing supplier and make up a remote mount above the metal box that it was all in, as a permanent fix.
But again, thanks to Mike for his generosity, allowing me to get back to welding Ally,
rgds,
Crocy.

[mike48]

Hi Crocy,

Glad to hear the good news.
Can you let me know the physical dimensions of the old capacitor, and its markings please.

And ... greetings from Abu Dhabi in the UAE, where I am visiting and staying with family, and where they do not have a Bunnings nor Jaycar.

cheerio, mike