DIY Metcal 13.56 MHz RF Supply

[calexanian]

Made up an adapter cable at the shop today to connect my Metcal MX hand piece directly to the output of my Yaesu FT-1000D. Tuned to 20 meter (14.100 to be exact) and put a whopping 10 watts carrier on it and hit the auto tuner and bingo! I turned the tuner off and it actually is a reasonable enough match. I did not look up at the meter but it did not trip the automatic protect and the auto tuner brought it to 1:1 in a split second so it was happy. At about 20 watts carrier the tip started getting a tad hot but at 10 to 15 it actually did some nice soldering. Unfortunately the going rate on a FT1000D is about 2 grand or more these days so i will stick with the MX 500 unit I own, but the exercise tells us that matching to these tips is really easy and they are not picky on frequency. Tomorrow I will be ordering some 12 volt pills (Look that up you young whipper snappers) and building a oscillator and power amp that I can run off a battery.

[Tazz]

I think the most useful option would be a board that has enough onboard to be useable standalone with maybe just a couple of LEDs as the user interface (maybe RGB), but that people can add their own add-on if they want anything clever like a display etc.

With the power supply section included, you mean? If so, that is basically what i had in mind. Make it a bit bigger to put the rectifier and voltage regulators there, so it can be used stand-alone, plus the header to connect to some more fancy stuff if one wants.

Greetings,

Chris

If it get done, you could add one or two unit for me in your batch

[dfnr2]

Just in case anyone is interested, I had 10 sets of PCB's made a while back, but never had the chance to play with them.  I would like to revisit the project sometime, but I have a different design in mind.

They are 2 layer 1.6mm (0.062") FR4 with green solder mask and silk screen on both sides.  I am happy to offer them for my cost, which was about $10 per pair, plus postage to you.  PM me if you are interested.

Dave

[CristopherD]

Pm sent

[Verydeep]

Good day!
My name is Sergey. I am radio amator from Russia.
I am trying to repeat this device. Can somebody say will  IPP530N15N3G MOSFET from Infineon work properly in power amplifier?
Can You give me recommendations on other components used in RF stage?

Thanks.

[peter.mitchell]

Actually mate,  you just happen to be one lucky sonofagun,  RS components singapore sells the metcal advanced handpeice for $115sgd free express delivery.  No joke.

Also,  I'm in the process of doing a bit of a board redesign,  removing all the unnessecary stuff and integrating it all.
If you want,  when I get my final design boards back I can send you one and a BOM (or even the parts inc if you pay,  ill just add them to my order quantities)

[peter.mitchell]

http://singapore.rs-online.com/web/p/soldering-iron-accessories/6750708/ link

[tom66]

Use a hobby RC Li-Po pack. I have a 11.1V (3S) 1050mAh pack here, costing $4.50 from HobbyKing in Hong Kong. It can supply 11 amps continuously and about 45 amps burst.
Make sure to add a protection circuit to prevent overdischarge (<9V for pack) and fuse the input. They can supply a scary amount of power into a dead short.

[peter.mitchell]

In my design, for a wide input range there is a LT3791-1 buck-boost converter, provided you can supply the current, the iron will run at full power from as low as 6v all the way to 55v, it will start up at as low as 5.5v and once started it will provide around 15w from 3v!

I'm at the stage in design/layout where i'm tweaking, trying to get certain things to work 100% (like auto power off), and get the heat dissipation all the way down so no special enclosures or big heatsinks are needed.

[mamalala]

just to add something on the sub topic of making at portable. i was quite amused to find a low voltage mosfet that is quite fast, so i thought i have a go at it in a simulation (note its not accurate) (R9 = soldering iron load, i tried to measure its DC resistance, it was about 1.3ohms).

Yeah, the only problem is that the DC resistance has no meaning in RF-land. A cold tip has roughly 50 ohms impedance at that frequency, according to a friend of mine who checked it out on a spectrum analyzer. So you need to drive that load, and not the 1.something ohms you see at DC.  That's the reason for the transformer and stuff in the circuit. At the output, during heat up, you can get voltage in excess of 100 volts p-p.

Greetings,

Chris

[AndersAnd]

P.S. Why you use IRF510?
It has a 0.5ohm internal resistance, may be something similar to IRFb4019 with 0.008ohm be more efficient?

P.P.S. Sorry, IRF630/IRF640/IRF740 i mean. Still, it is a UHF modulator

Basically for two simple reasons:

- RF circuits are not really my field of expertise, so for the initial design i limited myself to the types that i had already used once in circuits operating at the same or higher frequencies, so i would know they should work in that application.

- Because i wanted to reduce the overall complexity of the circuit, i chose to use a readily available FET driver chip instead of the much more complex driver circuit used in the original Metcal supply. However, that chip is very tiny, and to avoid overheating i chose a FET with a really low gate charge and capacitance.

(Edit: Of course i might have been too paranoid with that. I just chose to stay on the safe side so i can get something to work correctly)

Of course that is not to say that only the IRF510 would work. But since i lack proper equipment to really evaluate other FET's, it would be up to others to see what else can be used there. The IRFB4019 that you mentioned looks interresting. It has even faster switching times, while still having a relatively low total gate charge. Might be worthwile to experiment with that one.

Greetings,

Chris

I've just repaired two MX500 power supplies (won at an eBay auction), with the help of the schematic and documentation here: https://www.mikrocontroller.net/attachment/193474/MX-500P-11.pdf
Mirror: http://scopetechniques.com/Metcal/MX-500P-11.pdf

The documentation says:
Q3 = VN0109N5 http://scopetechniques.com/Metcal/465-1342-0-VN0109.pdf / http://scopetechniques.com/Metcal/VN0109N5.pdf
Q4 = IRF530(N) http://www.irf.com/product-info/datasheets/data/irf530npbf.pdf

But in the two defect MX500's I bought they were different:
Q3 = IRF510 http://www.irf.com/product-info/datasheets/data/irf510pbf.pdf
Q4 = IRF640N http://www.irf.com/product-info/datasheets/data/irf640npbf.pdf
Both branded International Rectifier.

The amber/orange led lit up all the time in my two defect devices while the green led was always off.
I found out Q4 was shorted in both devices and after replacing it with a new IRF640N both devices work again.
It looks like Q3 (IRF510) had been replaced before in at least one of the devices, so not sure if they came with Q3 = IRF510 and Q4 = IRF640N from the factory. But it seems to work, at least so far.
Has anyone else seen an MX500 with Q3 = IRF510 and Q4 = IRF640N?
Looks like VN0109N5 from Supertex is obsolete, so maybe Metcal started using IRF510 instead?
Now when you search Supertex.com VN0109 seems to only be available in wafer / dies and TO-92 housing called VN0109N3, but no TO-220 option.
And for Q4, IRF640N is a 200 V MOSFET, while IRF530(N) from the schematic is only rated at 100 V, so maybe they have replaced it because there was problems with too high voltage spikes, toasting the IRF530's? Doesn't look like IRF530N is obsolete.
Haven't done any measurements after repairing them, so not sure about the voltages Q4 handles? But since the IRF640N was toast in both of them, maybe that's not the issue?


Much to my surprise I also received a Metcal solder stand with the defect power supplies, even though this wasn't advertised. A very nice surprise as Metcal solder stands are actually very expensive and I didn't have any. Later I received a new and very nice MX-H1-AV handpiece as a birthday gift.
This came from RS Components where MX-H1-AV seems to be quite cheap compared to many others for some reason, even though RS usually isn't know for being cheap. So if anyone needs a new MX-H1-AV alloy handpiece for your DIY, Metcal or Thermaltronics/Easy Braid power supply, try to check out the price at you national RS Components site.

[AndersAnd]

Also posted this in another topic here: https://www.eevblog.com/forum/projects/broken-metcal-rfg-30-soldering-base-unit-fixed/msg438916/#msg438916
But thought I would post it in this DIY topic too, if someone wants to make their own Metcal hand-piece clone.
It's a bit hard to see what value the capacitor has, can anyone see what capacitor this is?

Isn't there a feed-through capacitor instead of a series capacitor as we talked about earlier from here onwards: https://www.eevblog.com/forum/projects/diy-metcal-13-56-mhz-rf-supply/msg310381/#msg310381https://www.eevblog.com/forum/projects/diy-metcal-13-56-mhz-rf-supply/msg310381/#msg310381

From what my friend told me, there _seems_ to be none, according to the analyzer. Of course something could have gone wrong, and there is one and he just missed it, i don't know. After all, there is also the capacitance from the cable, so that any internal cap was simply "hidden" due to that.

Greetings,

Chris

Found these old pics of a disassembled Metcal MX-RM3E https://imgur.com/a/RvDVu#0
They were posted in this topic in Oct. 2012: https://www.eevblog.com/forum/reviews/for-jbc-fans-out-there-jbc-tips-anatomy/msg151939/#msg151939

The last pictures shows there actually is a small capacitor in parallel with a 22µH inductor.

[mamalala]

Thanks for the images. That's rather strange then, i think. The images do not really match what i was seeing in the original patent, and it does not match what can be seen in the drawing you posted either. In the original patent, it looks as if there is only one capacitor, in series to the element. In you drawing, it looks as if a cap (38) is in parallel to a serial combonation of inductor (39) and element (41) (assuming that 36 and 37 are the feed-in ponts of the RF signal). But then, in your photo it looks as if there is a parallel combination of capacitor and inductor, which in turn is then in series with the element.

Really strange... Who knows, maybe they changed the design several times? If that stuff is still there today, then i guess my friend simply missed it when testing the handpiece on the NA.

Greetings,

Chris

[3roomlab]

i have a tricky question.

i once read in ARRL handbook about using a length of coax as VSWR sense by slipping in 1 or 2 more sense wires under the braid, so instead of having the PCB trace as the sense, i know the coax would work ... but im not sure how to calculate the length of this coax ... ? 1/4 lambda = approx 215inches ! so i dont think its based on wavelength?

i saw this version http://www.njqrp.org/qhbextra/3/3.html75.jpg
which could possibly reduce the size of the sense segment, but im not sure how

[richard.cs]

Hi All,

Just wondering if anyone's still working on this? It's on my to-do list but other projects keep cropping up.

3roomlab - it doesn't have to be a 1/4 wave, what you're making is a high impedance transmission line (the inner of your sense wire agains the braid through the thickness of the sense wire's insulation) with a weak coupling to the main coax. The strength of the coupling is dependant on length (proportional for lengths << than lambda) but calculating the exact value might be tricky. It's an interesting idea and I might throw it into HFSS at some point to see how it looks.

Richard


Edit: Results for the coupler

I modelled stuffing a bit of wire up the braid of some RG58, assuming that it just stretches out the braid. Wire was 1 mm OD PVC with 0.2 mm copper inner. It distorts the impedance of the coax a bit (I got 73 ohm) and looks like 60 ohms against the braid. Both are close enough to 50 ohms not to care about it too much* :-). Over a 100 mm length the forward coupling was -56 dB and the reverse coupling was -96 dB. This works better than I expected although the coupling is pretty weak. :-)


*If it was 73 ohms all the way then S11 looking into the main coax would be -15 dB, but for a short (100 mm) length that carries on in 50 ohms afterwards it's more like -50 dB.

[mamalala]

Hi All,

Just wondering if anyone's still working on this? It's on my to-do list but other projects keep cropping up.

Yes, i do, sometimes. I'm in the process of a major overhaul of the circuitry and layout, to (hopefully) simplify and improve some things. However, right now i can't spend much on any prototyping stuff, so it will have to wait for a while. Once i got something to show, i will probably open a new thread for the version 2 of this supply.

Greetings,

Chris

[David Hess]

A lateral power MOSFET like those made by Semelab might make a better replacement.

[zayance]

Hi There,

I made a small batch of PCB's for this project.
I'll need only two of these, and since i won't be needing the spares i have, i tought of proposing them here.
I have 11 in Stock right now

Please don't hesitate to send me a PM if interested, as i really would like to get rid of these.

PCB Silkscreen for the RF generator (not the controller) has been moved in numbers since it was imported and assembled as a panel in Eagle (little mistake)
BUT BOM / Build instructions and Schematic were modified accordingly, so won't be a prob, i can email these to print for people that bought the boards of course.

it would be possible to include some of the hard to get bits, scroll down for Reichelt Shopping card,
link to the updated BOM sheet with manufacturers n°:
https://docs.google.com/spreadsheet/ccc?key=0Al25JwaqoqLrdENzU05vQlZHYThWemVJOHRIbU9Zamc&usp=sharing


PRICES: (again it's a non profit action, just adding numbers)

I'm making the PCB price incl. all, PPfees and Shipping worldwide (for sake of ease):

One PCB (Controller board + Generator) : 21Euros
Two PCB's (controller board + Generator) : 41Euros

for info:
PCB MFG Price: 16.5Euros
Shipping Worldwide: 2.8Euros to 5.75Euros (depending on quantity)
PPfees: +4% ( i make this one a little higher because Paypal can be off sometimes)

Depending on interest, "Hard to get Bits" prices will add up in a Group Buy manner etc...

It would be possible to add these kind of Small dissipators on the list too, but might check somewhere else to avoid LARGE Shipping time
http://www.ebay.com/itm/5pcs-13x13x11mm-High-Quality-Aluminum-Heat-Sink-For-Chip-Electronic-H36-/181109747336?pt=LH_DefaultDomain_0&hash=item2a2afb6e88


For cutting them apart, you'll still need to cut, with a saw, some "plain" parts on each end before beeing able to break apart.

[zayance]

For now only two folks interested, and 8 PCB's left.

Anyone else?

[Precipice]

I'm one of those two. If anyone's keen, but can't face the surface mount soldering, I'd be happy to run their boards through the machine as I do mine. No guarantees of quick turnaround, and I'd only do the surface mount. Proper lead-free solder & machine placement, though.

[peter.mitchell]

Hi There,

I made a small batch of PCB's for this project.
I'll need only two of these, and since i won't be needing the spares i have, i tought of proposing them here.
I have 11 in Stock right now

Please don't hesitate to send me a PM if interested, as i really would like to get rid of these.

PCB Silkscreen for the RF generator (not the controller) has been moved in numbers since it was imported and assembled as a panel in Eagle (little mistake)
BUT BOM / Build instructions and Schematic were modified accordingly, so won't be a prob, i can email these to print for people that bought the boards of course.

it would be possible to include some of the hard to get bits, scroll down for Reichelt Shopping card,
link to the updated BOM sheet with manufacturers n°:
https://docs.google.com/spreadsheet/ccc?key=0Al25JwaqoqLrdENzU05vQlZHYThWemVJOHRIbU9Zamc&usp=sharing


PRICES: (again it's a non profit action, just adding numbers)

I'm making the PCB price incl. all, PPfees and Shipping worldwide (for sake of ease):

One PCB (Controller board + Generator) : 21Euros
Two PCB's (controller board + Generator) : 41Euros

for info:
PCB MFG Price: 16.5Euros
Shipping Worldwide: 2.8Euros to 5.75Euros (depending on quantity)
PPfees: +4% ( i make this one a little higher because Paypal can be off sometimes)

Depending on interest, "Hard to get Bits" prices will add up in a Group Buy manner etc...

It would be possible to add these kind of Small dissipators on the list too, but might check somewhere else to avoid LARGE Shipping time
http://www.ebay.com/itm/5pcs-13x13x11mm-High-Quality-Aluminum-Heat-Sink-For-Chip-Electronic-H36-/181109747336?pt=LH_DefaultDomain_0&hash=item2a2afb6e88


For cutting them apart, you'll still need to cut, with a saw, some "plain" parts on each end before beeing able to break apart.

Just curious who did your pcb manufacture with the matte black silkscreen and enig, they look beautiful!

[zayance]

It's a China based manufacturer, nice quality and good service.
But i've seen other manufacturers based in Asia having similar quality.
Now for double sided, and maybe a little more they sem to be good, can't tell
for any complex stuff tough.

http://www.pcbcart.com/

[peter.mitchell]

It's a China based manufacturer, nice quality and good service.
But i've seen other manufacturers based in Asia having similar quality.
Now for double sided, and maybe a little more they sem to be good, can't tell
for any complex stuff tough.

http://www.pcbcart.com/

Ahhh, ive used pcb cart before - although they didn't have matte black soldermask then?

[mamalala]

Hi all,

just wanted to say, zayance sent me those PCB's and they look just great! Thanks very much for that, zayance!

If you plan to build one, go for it. Right now i'm rather busy with other stuff, plus i'm short on funny-money to spend on private projects right now, so the next version of the supply board will take some time.

Greetings,

Chris

[zayance]

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