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Thread: Weller EC2002A/EC1201A Soldering Station repair issues

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    Senior Member nevetslab's Avatar
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    Weller EC2002A/EC1201A Soldering Station repair issues

    I have an aging Weller EC2002A/EC1201P Soldering Station, having the digital readout for setting/reading tip temperature. Some time back, it stopped working, both the Triac inside had failed, as well as the digital display failed. I finally got around to getting it back up and running, beginning with replacing the Triac. A Q4006F41 was installed, it being a TO-202 package. I removed the part, found a suitable replacement (BTA-16600CRG, being a 16A/600V part replacing the 6A/400V part. TO-220, but the pinout was the same. I also replaced the 7805 TO-220 5V regulator on the Display board, then re-mounted the two PCB’s and powered it up. I now had heat on the working EC1201P Iron, had 5V on the display board, but still no display.

    There are two IC’s…a CA3161 and a CA3162. The CA3162 is an A/D converter for 3-1/2 Digit Voltmeters, and the CA3161 is it’s companion BCD to 7-segment display driver. I was getting no function on the CA3162, so I went to see what I could find on line. Discontinued parts, so off to see what was available. Prices ranged from $7 to $50 on the CA3162. I tried one of each in the $7 range, coming from China. The CA3162 that arrived didn’t work, but it did make two of the display digits partially light up. I ordered another from a different vendor, and that one DID work.

    I had installed IC sockets during the removal/replacement process, but found I had to hack away at the plastic ribs in the innards to get the socketed IC’s to fit. Got that done, put it back together, and powered up. Now what I found is I can set the temperature as normal, but…..the Read mode isn’t tracking at all. Set for 750 Deg F, switching over to Read, it slowly drops down and settles around 492 deg F.

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    I moved the EC1201A over to my Weller EC1000 Base unit, which just has a RED LED that lights up when it hits temperature, and will flash during the thermal cycling while regulating it at the target temp set with the control. And, of course, it melts solder just fine.

    With the iron back on the EC2002A base unit, it too melts solder just fine, though I don’t know what the tip temperature is. I checked with my Fluke 51 Digital Temp meter with a surface probe 80PK3A, but it’s only rated to 500 deg F. That’s also the limit of my older Fluke 51.

    weller-ec2000A-manual.pdf
    Weller_EC1201P_Handle_Disassembly.pdf

    I took the EC1201A Iron partially apart, wondering if I was dealing with a Sensor issue. The RTD Sensor shaft, which protrudes inside the hollow cavity of the Weller ET-series tips was noticeably darkened & crusty looking. I wire-brushed it to look clean like the base of it's shaft, not knowing if that had anything to do with it. No change. I have a second EC1201A handle, as well as a spare heater unit and a sensor unit that had been unsoldered from one of the handles....don't know the status of it. I did swap out the heater unit, though that made no difference. I wasn't able to release the strain relief of the silicon rubber cord of the iron, so I didn't pursue that any further. Since the iron works fine in the other base unit, I'm pretty sure it's not in the iron.

    I was able to find & download the Weller Tech Sheet for this model, which includes a Calibration Check procedure as well as a Recalibration Procedure. I haven’t yet tried to go thru that. It involves a couple Calibration resistors, both based on what ET series Tips are inserted into the iron. That’s easy enough…36.4 ohms and 51.4 ohms, so I’d have to select/trim those from available resistors. A third resistor is required,a 13 ohm 40W load with an indicator light across it (24V incandescent lamp). I’ve yet to cobble that load with lamp together to try and re-calibrate this.

    What I’m also seeing is, unlike what I recall it doing when powering up, the tip temperature in Read mode would climb right up fairly quickly….say hitting 750 Deg F inside 40 seconds. It’s now taking a few minutes to get around 486 deg F, where it’s sitting now.

    Has anyone ever gone thru servicing these, as well as the re-calibration ?

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    Last edited by nevetslab; 01-10-2019 at 12:25 AM.
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  2. #2
    Don't forget the joker g1's Avatar
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    Have you verified that the display board is getting info that corresponds to the reading?
    If that second chip was also from China, I would not count on the display board being fixed yet.

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  3. #3
    Senior Member nevetslab's Avatar
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    Quote Originally Posted by g1 View Post
    Have you verified that the display board is getting info that corresponds to the reading?
    If that second chip was also from China, I would not count on the display board being fixed yet.
    I am getting valid reading from the Vref thru the calibration trim pots, thru the Set control, and see the set range is in the range of 350 deg thru 850 deg The Read path is by way of the RTD sensor in the iron, thru a different resistor network and trim pot and on down to the display board. There are additional trim pots on the display board, as there are on the control board. I'm willing to believe the A/D chip is doing its' job, and more suspect of the control board, and the circuitry that controls driving the Triac to keep the iron at the desired range. But, that's just me wishing it were so, I guess. If I wasn't seeing an adjustment range in the ballpark with the system's temp setting range, then I'd suspect the A/D chip.

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    Display Min-Max Set Range, Tip Temp via Temp Meter

    Checking the present Min/Max Temp Set Range with the new A/D Chip in place, I'm seeing the Min temp in agreement with Weller's spec, while the Max temp is a bit above their 850 deg F spec...nearly 900 deg F.

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    Since my Fluke Model 51 has a limited Temp range, as does my Fluke 80PK-3A Surface probe, max of 500 deg F, I looked to see what I got when I set the Weller station to 500 deg F, with a fresh wetted surface of solder on the tip, pressed down on the surface probe, held in a small machinist vise while taking the picture.

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    Over the years of active use with this Weller Station, I never had to dig inside to change anything, and only have had to replace a heater, and from parts left over in my Weller Parts box, have replaced a Sensor assembly as well inside the iron. I've never even checked to see if the tip temp was correct or not, as the readings were usually within the 'nominal window' of the Set Temp, and know under thermal load, that temperature will vary and recover when set back into the holder. This is just the first time I'm seeing deviation from what WAS, beginning with restoring the Triac that is controlling the heater...............

    Hmmmm. I didn't have an exact replacement Triac, but used a different Triac to restore it to working status. I wonder if that could be the problem? It was a Q4006F41, a 6A/400V TO-202 part. I installed a 16A/600V TO-220 part. The Triac is in the Temp Reading control loop! Does that sound like the issue?

    In searching for the Q4006F41, I find it's an obsolete part as of 2007. I did find a US source for it for $1 ea, ordered 3 pcs, so I guess we'll see when they arrive.

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    Last edited by nevetslab; 01-10-2019 at 07:49 PM.
    Logic is an organized way of going wrong with confidence

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