WELLER WHA-2000

[PermBan]

Hi guys!
I'm struggling to fix my Weller hot air station.
I bought it to start doing things myself and begin my adventure with electronics, but I was scammed and the device doesn't work. Do you have any advice??
The device doesn't produce hot air.
Everything turns on, the air blows, but it's cold.
Where should I start?
The heater in the gun shows resistance in kilo-ohms.

[tunk]

Maybe open it and post some photos?

[PermBan]

I think I found the cause of the malfunction!
But where can I buy such a fitting part now?
********
another photo with measurements:
diameter is 17.1/17.2mm
length is 40mm but
what resistance?
https://ibb.co/2SM4Wnc

[thm_w]

You can measure the resistance with a multimeter. Or look at the wattage consumption, determine what length of wire you'd need to use to draw that much power.

What do you mean diameter is 17mm, what is the diameter of the wire? It is probably nichrome wire.
Nichrome or kanthal is fairly cheap to buy, but its a bit of a pain in the ass to bend the wire to form those loops and recreate the whole heater. Compared to a new 858D for $40.

[PermBan]

Yesterday I bought a wire, but what should I wind it on to make sure that the diameter of the winding does not exceed two millimeters?
So that I can later insert this coil into 2.5mm holes?
Please take a look at my first picture.

[Nominal Animal]

Grab some calipers, and measure the thickness of the wire.
Subtract twice the the thickness from the outer diameter you want, and you have the desired inner diameter.
There will be a bit of springback in the coil –– from almost nothing to quite a lot, depending on the wire and how you wind it ––, so you'll likely have to experiment a bit (towards a thinner core than the desired inner diameter).

Your most important tool here will be calipers or a micrometer, to measure things; plus a couple of different radii cores to wind around.  You can use metal wire of suitable 1-2mm thickness (I'd start with 1.5mm) as the winding core, if you tighten the other end around a screw or something, and pull it tight (pulling it straight) on the other end using a vise or similar.  You can find suitable core wire at hobby stores and hardware stores; just take your calipers with you and go look.  You don't need that much, less than a meter, so it won't cost you much.

It is likely the coil will expand a bit when it heats, so you'll definitely want your replacement heater coils to match the original ones as best you can.  This is also why the coil isn't stacked tight.

As already mentioned, take one of the existing heating coils, and measure its resistance from end to end.  You'll want your replacement coils to have the same resistance (and thus the same heat output at the same voltage and current) as the originals.  Note that because this is a relative measurement, you don't need an expensive precise multimeter for this; one that has sufficient resolution at the low end will work just fine, as the coils have likely just a couple of ohms of resistance.

[PermBan]

Thank you for your time and response
One section of the winding has a resistance of about 3.7 ohms after deducting the probe resistance (0.6 ohms) of my FLUKE.
Yesterday (12/05/23) I purchased resistive wire and I hope it will be sufficient.
The manufacturer of this wire promises durability up to 1200 degrees Celsius, so I think it should be enough.
LINK: https://wireandstuff.co.uk/product/0-4mm-26-awg-ni80-nichrome-heating-wire/
A cheaper version of this resistive wire is supposed to withstand 1150 degrees Celsius.

Please let me know if you have any other ideas 
Maybe someone has such a heating element lying in a drawer?
Or have you come across an auction where I can buy such an element?
I wrote to WELLER, but they probably don't care about me and my device because they are focused on selling new soldering stations and equipment :'(

[Nominal Animal]

I found a diagram of the Weller WHA 2000 at labem.pl:


If I understood correctly, you are looking to fix or replace the heating cartridge, Weller part number 58736795.  I would just ask from Weller how much a spare (new) heater unit would cost.

[PermBan]

Thank you as well for your response and your time
No, my friend, I need the interior part with the number 53312699, and the part number 58736795 seems to be the turbine.
I have this diagram, but it doesn't provide enough details

[Nominal Animal]

No, my friend, I need the interior part with the number 53312699, and the part number 58736795 seems to be the turbine.

Oops, sorry 

The 5 33 126 99 seems to be called "Hot air pencil HAP 2" running at nominal 230 V with up to 700 W power.

(Perhaps fire up an email to repair-center (the address is just under the personnel pics here), asking if one can buy a replacement, considering the product line is discontinued?)

I didn't find anyone selling these online, but it is quite possible Weller or some of its distributors have replacement hand pieces still in stock; after all, this is professional soldering equipment.
 _ _ _

Let's do some math.

First, we know the voltage is 230 V (RMS) and power 700 W.  This means the total resistance of the heating unit is 230²/700 [V²/W] ≃ 75 ohm.
This is actually in 18 sections (with a little bit of wire in between, for 4.3 ohms per section), but a single length of wire.  You cannot really join two pieces together: solder will melt, and crimped connections won't hold due to the thermal expansion and contraction.

0.4mm/26AWG nichrome 80 wire has a resistance of 8.0 to 8.9 ohm/m, let's say 8.4 ohm/m.  Thus, the entire heating coil will need between 8.4 m and 9.4 m of wire.

If the outer diameter of the coil/helix is 2mm, the inner diameter is 1.2mm, and centerline diameter 1.6mm.  Each turn is therefore about 5.0mm, and the entire coil will have about 1800 turns: 100 turns per section.  When closely packed, 100 turns of 0.4mm wire is 40mm.

However, the actual power as calculated above may be higher, if the control unit limits to less than 100% duty cycle (in the triac chopping the mains voltage).  If the per section resistance is 3.5 ohms, the total 100% duty cycle power would be 840 W (20% more), and whole-coil resistance 63 ohm; about 7.5m of 0.4mm/26AWG nichrome 80 wire.

If the outer diameter of the coil/helix is 2mm, there would be about 1500 turns, or about 80 turns per section (with about a turn in between sections as a straight wire).  This sounds more plausible than the above, since the coil is no longer tightly packed.
 _ _ _

I personally would cobble together a rig to wind the entire coil in one long section, then measure (resistance) where the 17 straight sections are.

The entire coil will in all cases be at most 18×40mm = 720mm long.  I'd bolt two rod ends at about 80cm from each other through some plank or rod, with ring bolts through the bearing hole, core wire carefully attached to the rings, and tension the 1.2mm core wire between the two using nuts on the ring bolts.  I'd use two nuts per ring bolt, jammed.  The setup can be rotated from either end using e.g. a cordless drill, so it is a good idea to use longish ring bolts.  I'm right-handed, so I'd keep my left hand on the trigger, and with my right hand carefully tension and feed the nichrome wire onto the core wire.  The initial 10-20 turns may not work out too well, so this would be the trimmed end.

Next, I'd pull the coil off the core, and stretch it a tiny bit: just enough to separate the coils, making it a helix (turns not touching each other).

Then, I'd measure the resistance of the first coil section (3.5 ohms using your DMM), then unwind about half a turn for the next section, and push the rest of the coil through the next section hole.  Each following section I'd measure the resistance from the previous straight part (the same 3.5 ohms using your DMM), then unwind the half-turn or so needed for the intersection part.  If all goes well, you end up with a section of unneeded helix, which I'd just cut off.
You could also count the turns, but I would probably mess up the count.

I am only a hobbyist, so there are no guarantees this will work, though.

[PermBan]

I have read it and I am impressed
Although I have never coiled wire into a spiral, a similar plan has formed in my head. I have a problem with such a long wire and a diameter of 1.2mm or less!!
I will try to use a drillbit to achieve this goal and build some kind of device that will correctly arrange the first few turns. The wire already wound should push out the finished coil - that's my plan.
Or maybe I could order such a coil from you?
Maybe you have better skills?

[Nominal Animal]

Although I have never coiled wire into a spiral, a similar plan has formed in my head. I have a problem with such a long wire and a diameter of 1.2mm or less!!
I will try to use a drillbit to achieve this goal and build some kind of device that will correctly arrange the first few turns. The wire already wound should push out the finished coil - that's my plan.

Yep.  Keeping the wire taut as it is wound to the core is key, methinks.  I have not coiled nichrome 80 myself, only copper coil/transformer wire a couple of times (and although the result worked, it looked like it was made by a baboon on drugs).

Maybe you have better skills?

No way, I'm an uncle bumblefuck myself.  However, we are all newbies once; all it takes is practice.  So, what I would do, is just get an extra 10m or so of the same wire (knowing it costs under 3 UKP at wireandstuff.co.uk), and practice.

Some kind of a coiling jig is absolutely required, though.  There are quite a few ideas on Youtube for this, although here the core is really small – 1.2mm, like you mentioned.  I'm wondering whether the jig should have only a short section of core exposed, then an outer tube (rotating with the core), keeping the coils tight somehow?  Dunno, needs experimentation!

[Nominal Animal]

I have an idea on the coiling:

Pre-form the coil on a M2 threaded rod.  The standard pitch is 0.4mm, so it should coil perfectly; i.e. the coiling should be very, very easy.  Then, you just need to tighten the coil around some 1.0mm - 1.6mm rod/wire, to reduce the outer diameter.

You can find M2 threaded rod on eBay.co.uk and elsewhere for about 2 UKP per 30-50cm length.

[PermBan]

Thank you all for every suggestion
Today 20/5/2023 I just received the resistance wire, but I'm after the night shift  (12hrs) and the barbecue is almost ready, and there's whiskey 
I will inform you about the attempts to make the heater next week.
I have a wire labeled "Ni80 Nichrome" of 10 meters. I still have DOUBTS about how to test the finished winding because it is very difficult to insert the heater into the gun.
The heater was wrapped in some material (in the picture) that is now very brittle. Does anyone know what it's called?
If I fail or if the heater burns out after one minute, I won't have anything to seal the heater in the gun. Does Kapton tape not work for this purpose?
What is the minimum length of "Ni80 Nichrome" wire to prevent it from exploding when connected to 240 volts? I know I should find this information on the manufacturer's website, but I'd like to have this heating element now, and after the night shift, I'm feeling lazy, plus the barbecue is ready. Would anyone be willing to help me out?
THANK YOU! HAVE A GREAT WEEKEND.

[Nominal Animal]

I have a wire labeled "Ni80 Nichrome" of 10 meters. I still have DOUBTS about how to test the finished winding because it is very difficult to insert the heater into the gun.

Just measure the resistance using a multimeter.   If it is between say 50 and 75 ohms, it should be okay.

The heater was wrapped in some material (in the picture) that is now very brittle. Does anyone know what it's called?

Looks like mica (phlogopite) sheet.  It is an insulating material often used in electronics. It is not expensive at all, although as a hobbyist, it can be a bit annoying to try and source (since it's mostly sold in large batches, as it is a cheap and common material, commonly used as e.g. heatsink insulators with transistors, MOSFETs, and large diodes).

If only McMaster-Carr delivered to UK!

If I fail or if the heater burns out after one minute, I won't have anything to seal the heater in the gun. Does Kapton tape not work for this purpose?

Kapton can only handle up to 400°C, whereas mica, even at under 0.1mm thickness, is thermally stable stable at up to 500°C (930°F), and phlogopite is stable at up to 900°C.

I would definitely use mica here, phlogopite if possible, and not kapton or other polyimide tapes.

What is the minimum length of "Ni80 Nichrome" wire to prevent it from exploding when connected to 240 volts?

Don't.  Even the hot air station pulses the voltage, it doesn't just leave it on at 240 VAC.  You'll just burn (break) the wire.

Consider what happens when you put a 9 VDC across a half a meter long section.  The resistance is a bit over 4 ohms, so the current is between 2 and 2.5 amperes; that half a meter section will then convert about 20 watts to heat.  That makes for a pretty good foam cutter, with a half-meter "blade".  Even this might be too much for the very thin 0.4mm wire, if there is no airflow across the wire.

(You see, the wire doesn't "explode", it just gets too hot and melts and breaks.  When there is airflow across the wire, the heat transfers to the air, and the wire itself stays cooler.  With a thermocouple or PTC (Pt100 or Pt1000) temperature sensors in the block and/or in the following airflow, the station can manage the airflow temperature and ensure the coils don't overheat and burn.  You'll notice that (all) hot air stations will blow air for a short while after the heating stops: this is to help with the heating coil longevity, by cooling it down.)

Like I said, do not do this, instead just measure the coil resistance using a DMM.  It is just resistive wire, after all.

[PermBan]

Since purchasing this device, I haven't been able to find anything of approximate size for the required heating element - maybe I'm not searching well enough :/

However, after negotiations and several emails with the seller, I have ordered a rod (considered the best and hardest by the seller) that will serve as a 'mold' for creating the coil.
I will keep you updated on the progress.
THANK YOU ALL!