DIY Metcal 13.56 MHz RF supply

in DIY, power supply by DP | 8 comments

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Chris over at the EEVblog forum designed and built this DIY Metcal 13.56 MHz RF supply:

A while ago i came up with my own circuit for that, plus some nifty firmware (which basically is optional). You can see what i have done so far on the EEV-Blog forum here

As of recently the whole thing is working. I know that the Metcal system is more of a niche thing, but i think quite interesting none the less….

Via the contact form.

This entry was posted in DIY, power supply and tagged , .

Comments

  1. Chris says:

    Hello,

    thanks for mentioning my project here!

    The above image is from the very first prototype i made. A more recent image of the current unit can be found .

    For anyone interrested, please read the whole thread over at EEVBlog, since there have been quite some updates going on. Or, if you just want the latest files and stuff, read the thread backwards.

    Greetings,

    Chris

  2. Megabug says:

    Brilliant stuff! Metcal soldering iron really ROCKS. Unbelievable if I wouldn’t be using one myself. Thanks Chris for that.

  3. Burning Tantalum says:

    I have followed this project with interest, and have largely got my head around most of the technical stuff. One area of electronics that I have little knowledge of is RF, though.
    Ages ago I acquired 3 Metcal MX500 units without soldering wands/irons. The wands are extremely expensive new and never seem to appear second-hand or dead. I take it that apart from the mechanical details they consist only of an inductor coil. Does anyone have an idea of specification and rough dimensions- it should be fairly easy to construct something; I even have a metal lathe!
    Regards, Tantalum

    • Chris says:

      Hi Tantalum,

      nope, the handpieces for the MX series are nothing more than a hollow hande with a connector inside, and a very flexible coax attached to it, ending in a regular F-type plug. The tips are a complete units, unlike the SP series, where you have a coil assembly in the handpiece (or, well, at least that is what i understand from the SP stuff). The SP handles and tips are not compatible, they use a much lower frequency.

      So, to make a handpiece for MX, you basically just need to find a suitable plug-connector that can connect the tip cartridges, and put that inside a handle. Never really looked deeply into that, but i can imagine that one of those many miniature RF connectors could be used, there are many, many different types.

      Another problem, and a much bigger one i think, is to find such a soft coax cable. It has to be really soft, but at the same time able to handle eneough RF energy…

      Greetings,

      Chris

  4. Burning Tantalum says:

    Hi Chris,

    Thanks for the info- That has moved the project back up the list!
    I suppose that the best plan of action for me would be to purchase at least one tip ‘unit’ and work from there. Now I see why the tips are so expensive, but the handles…?
    I have always been a bit of a ‘soldering iron snob’, and know how much the flexibility of the cord affects the useability of the tool. I always liked the white silicone leads on the old Weller magnastats for that reason.

    Regards, Tantalum

    • Chris says:

      Hi Tantalum,

      well, Metcal is rather “rare”, so the production volume is lower, which drives the price up. And of course you also pay for the name. About the cable, it must be a coax cable. An unshielded cable will not work. However, i’m not sure yet if the cable is 50 or 75 ohms impedance. My guess would be 50 ohms.

      You can check on eBay, there are often used tip cartridges for a rather low price. I could also make a series of photos with dimensions, if you like, for the cartridges and the handpiece itself. Just let me know where to send them to. You may also ask one of the moderators here to give you my eMail address, so you can contact me directly.

      Also, check out U.S. patent 4,839,501 for more details about the handpiece (and no, the series capacitor mentioned in that one isn’t there in the real thing).

      Oh, and if you think the normal handpieces are expensive, take a look at the MX Talon tweezer ;) Just got one really cheap, wonderful thing.

      Greetings,

      Chris

  5. Burning Tantalum says:

    Hi Chris,

    Thank you once again for your time and trouble.
    I have had a ‘saved search’ on eBay for a long while now, looking for the RM3E and tips etc. I feel more inclined to bid a bit more for a tip now!
    Regarding the co-ax: Yes, I am aware of its necessity (industrial electronic engineer since training from 1974, but limited RF experience- mainly from Ham radio licence studies and interests), so if I manage to source a tip fairly soon I will have an experimental lash-up with some decent quality 50ohm and take it from there.
    Does the length of the lead matter ie multiples of wavelength (at propogation speed in the co-ax)?

    I have a list saved somewhere of all the different charcteristics and dimensions of the RG series, but suppleness is not one of the parameters!

    The patent info is interesting: It seems that Hakko also had a patent from 1994 with what sounds like a similar system- did they ever produce anything?
    The medical instruments are also of interest: It never occurred to me but it could be a source of flexible co-ax… a phone call to my sister, I think…

    I wouldn’t want to trouble you for pictures etc- It is only mechanical details, and a nice little project.

    I am retired now so only use my irons for hobby and repairs- I’m quite happy with my old Pace MBT iron and extractor, but don’t like to possess any tool, test equipment or engine that isn’t working 100%. Obsessive, I know!

    Thanks again, Tantalum

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