Whats inside Weller WMRT Tweezers

[Hydron]

Thanks for the info, knowing that I've looked at the photos I took when I opened my WXMT and I think I see the hole the pogo pin mounts in. Should be easy to add one in parallel to the normal earth connection so that the handpiece is compatible with either type of RTW cartridge. Will post pics if/when I mod it.

Now I need to make some decisions as to which cartridges to buy - has anyone got experience using the Non-Wettable options (e.g. RTW6NW), or the wide ones?
I'm assuming the former help stop the part sticking to the iron once placed/removed, and the latter are obviously for lifting SOICs/TSSOPs, but as usual Weller has very little info available and I have no experience as to how well they actually work at those jobs.

Edit: a reflection in the photo had me fooled - no hole there for pogo pin

[sariniitb]

Hi,

I have a WMRT soldering tool as part of  my W3M three channel unit. Worked fine for 5+ years. Recently it's been malfunctioning with a couple of symptoms:

• When the WMRT connector is plugged in, the temperature display shows 600C and gets stuck at 600C. The tips don't get hot though. Diagnosis: the KTY82 sensor in the handle is probably kaput (thanks for all the detailed info an pictures above!). I opened the handle, reflowed all the solder joints on the little PCB. Now the controls on the unit operate and set the temperature correctly in the 100 - 300C range (see #3 below)
  
• The left tip doesn't heat up - only the right tip does. The open circuit resistance on the connector is also different. [1-7] right heater is ~ 2 ohm, [1-2] is 1k. Diagnosis: a loose wire joint inside the tip connecting the high current wire to the heated tip metal? after all, if the solder joints on the pcb needed to be reflowed, maybe the wire connections inside the tip to be rechecked? Started to disassemble the tip and couldn't get further than the attached picture. Some flimsy wires can be seen routed around inside the tiny black cover : the tips themselves simply sit in the grooves)
  Any suggestions if I should try to disassemble the tip further?? Not sure it's possible to open it up in a put-back-together working manner!
  
• Tried reassembling anyway after wiggling the tips around in there slots, in case its a loose slip on connection inside. Now a couple of other problems present themselves: (a) the reed switch seems to act like the 'NOT' of what its expected to do. When the tip is in the holder, the control unit activates it, and when it is lifted up, it gets deactivated - annoying, but workable (with a magnet stuck on the handle)
  (b) intermittently, the control unit goes back to the 'stuck at 600C mode. Probably the KTY82 is indeed broken and will have to be replaced, or the one sided tip heating causes some control fault?
  

Our country is locked down, so lots of time to fix broken things in the lab with whatever parts I have on hand (lots of 'em, but no KTY82]. Any ideas on what to do about the non-working left side tip? and/or the temperature control?

Best regards -
Pradeep Sarin

[sariniitb]

I did go ahead and disassemble the RTW1 tweezer tips. Rather simple : the black cover with 'L' 'R' white markings is just a flimsy plastic/paper card bent and slipped around the mounting nut of the connector on the RTW1.
Popping it off, reveals another flimsy little PCB  (pic 1 below). The wires going to the heater tips are soldered on! Very un-German engineering. The actual tips are simply hanging above the PCB with the stiff wire carrying the heater current.

Probably the wires were touching or there was some gunk in the left heater wire (pic 2). Cleaned the whole thing with IPA, reflowed all the solder joints. Now as per the wiring diagram (pic 3) on the front-end connector X1,  I have equal resistance 3 ohm of the L/R heater wires (1,3) and (5,3).

Put it back together end-to-end (RTW1 -> mates to handle -> handle -> cable to Control Unit
At the 'station connector' in the wiring diagram pin 1-2 STILL shows 1kOhm. Very puzzling - it's supposed to be a straight wire through from X1 to the station connector. Unless I am missing some funny ground connection...

Plugged the WMRT into the control unit, and as expected from above diagnosis, despite the fondest hopes, the left tip STILL does not heat up (right tip goes to 300C fine.

[ksilabs]

I did go ahead and disassemble the RTW1 tweezer tips. Rather simple : the black cover with 'L' 'R' white markings is just a flimsy plastic/paper card bent and slipped around the mounting nut of the connector on the RTW1.
Popping it off, reveals another flimsy little PCB  (pic 1 below). The wires going to the heater tips are soldered on! Very un-German engineering. The actual tips are simply hanging above the PCB with the stiff wire carrying the heater current.

Probably the wires were touching or there was some gunk in the left heater wire (pic 2). Cleaned the whole thing with IPA, reflowed all the solder joints. Now as per the wiring diagram (pic 3) on the front-end connector X1,  I have equal resistance 3 ohm of the L/R heater wires (1,3) and (5,3).

Put it back together end-to-end (RTW1 -> mates to handle -> handle -> cable to Control Unit
At the 'station connector' in the wiring diagram pin 1-2 STILL shows 1kOhm. Very puzzling - it's supposed to be a straight wire through from X1 to the station connector. Unless I am missing some funny ground connection...

Plugged the WMRT into the control unit, and as expected from above diagnosis, despite the fondest hopes, the left tip STILL does not heat up (right tip goes to 300C fine.

Sorry for disappointing you but that heater is almost certainly dead so you will need another tip. Nothing to repair there, it is like a burned light bulb.

[sariniitb]

Not burnt out.

I was able to get it working by jumpering across pins 1 and 5 of the end connector X1 to which the two heating elements are soldered. Pic RTW1_1 above.
 Of course this means the two heating elements are running in parallel from the same current source, and pin 5 carrying current to the temperature sensor is carrying the wrong current, so the temperature sensing is a bit off.

But the bottom line is that now both left and right tweezer tips heat up - havn't been able to measure the temperature accurately : but its good enough to lift off a few components from a dense pcb I needed to disassemble.
Eventually will purchase a new tip.

I still don't understand the circuit control completely - why the reed switch is doing the NOT of what its supposed to do. Wants to keep the tips ON when it's in the holder with the magnet, and OFF when lifted. So for now, I popped off the magnet in the holder, and stick it on the WMRT when in use (it sticks by magnetic pull of the reed switch).

Just posting the final info here, in case someone finds it useful.

[mvcz]

I had similar issue with WR3M and WMRT tweezers:

The left tip doesn't heat up - only the right tip does.

In my case, the resistance of heating elements was OK. I tracked the issue back into the WR3M unit where blown fuses were found. See simplified circuit diagram of the power stage (the component names are fictional because there is no marking on the silk screen). Each of three channels have two independent sub-channels (left and right). The left sub-channels are primary and have 12V/24V capability. The right sub-channels are secondary and the 12V/24V capability is available on channel 1 only (high power channel for hot air gun HAP200 https://www.hackerspace-ffm.de/wiki/index.php?title=L%C3%B6terich&mobileaction=toggle_view_desktop#HAP200). The WR3M somehow detects correct voltage (based on resistance of the heating element???). The interesting thing is that there are no fuses in series with the 24V triacs. It looks like that the main reason is to protect in situation when both 12V and 24V triacs are turned on simultaneously. Anyway, the fuses F1, F2, F3 and F5 were blown for some reason (it is a shared equipment in a lab). Therefore, the WSP80 was running in each channel since it is 24V and the WMRT did not worked in CH1 and just right tip was working in CH2 and CH3. Replacing those fuses fixed the problem. The fuses are in SMD 2410 package directly soldered on PCB and there is no access when PCB is mounted in the chassis.

It is an old topic but it can be helpful for someone with the same problem ...

[costas]

WMRT schematic !

[psvabenik]

Hi,
has anyone experience with different versions of the WMRT (and WMRP) soldering irons? I am about to buy one to be paired with WT2M station. Unfortunately I find different types of irons, some are 12V, some are 24V. I am confused from Wellers datasheets, which statest WT2M outputs 24V.
Is all the irons both 12V and 24V compatible? Maybe it is just bad marketing, where the WMRT has two separate heaters, each working on 12V (so they sometimes call it "24V"). Or is is completely different iron for different market?
I do not have one available, at least I could measure the resistance of the heater (so I can calculate 2x40W power).
I was also looking into the connector pinout, but could not find pinout for WT2M. Anyway some seems to have both options available, 12V and 24V on same pins. Can someone take me out of the confusion? Thanks a lot.

[mahi]

psvabenik: The Weller WMRT and WMRP are both 12V tools. There has been a lot of confusion about the "24V" marked WMRT tweezers, but general consensus is that this is a mistake/misprint on the early hand pieces. None of the WMRT or WMRP will work on 24V-only stations like the WT1, WD1, WR2, WSD80,... The Weller WT2M on the other hand supports both 12V and 24V tools.

Weller makes a total mess of releasing seemingly similar or related stations, but that do not support all tools. Always consult a compatibility matrix before buying Weller equipment: WT station compatibility matrix.

[psvabenik]

Thanks. Yes, I have seen the compatibility matrix, but it did not make things any more clear.
I also sent two questions directly to Weller, but no response.

However local distributor was able to reach back to me and offered me instead of WMRT tweezers (not being produced anymore) replacement WTMT. Seems very similar, but with different internal connector and with different set of tips RTWMS group. These seems to work also with WXMTS tweezers, which are for WX stations. At least some unification is being done.

[eliocor]

to your knowledge, is the "obsolete" WD2M base compatible with the WMRT/WMRP irons/tips?

[PlainName]

I am using WMRT tweezers with a WD2M base.