Weller EC2002A/EC1201A Soldering Station repair issues

[nevetslab]

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.



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 ?

[g1]

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.

[nevetslab]

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.

[nevetslab]

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.



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.



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.

[nevetslab]

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? I did find a US source for it for $1 ea, ordered 3 pcs, so I guess we'll see when they arrive.

The Q4006F41 Triacs arrived yesterday, and I popped one in this morning. Didn't make any difference, so I guess I'll have to go the route of re-calibrating the meter circuit & tip temperature control circuit. I was hoping someone had gone thru that process before. I'll have to wait for another open time slot for that task.

[nevetslab]

The Q4006F41 Triacs arrived yesterday, and I popped one in this morning. Didn't make any difference, so I guess I'll have to go the route of re-calibrating the meter circuit & tip temperature control circuit. I was hoping someone had gone thru that process before. I'll have to wait for another open time slot for that task.

I had some time to begin the Meter Calibration procedure on this Weller EC2002A Soldering Station. I needed some small pins to fit into the soldering iron socket, and found I had some crimp terminals that fit that perfectly, so made some adapter cables to mate with my decade box, which would serve to provide the 31.4 Ohm Resistor A and 51.4 ohm Resistor B required in the calibration procedure. Used one of my dummy loads for the 13 ohm 40W resistor to simulate the soldering iron's heater. Now, their calibration notes states you need a 24V Incandescent Lamp in parallel with this 13 ohm load resistor, as in Step 11, you're supposed to adjust the Temp Control to where the lamp just stops flashing.

Hmmm.....no 24V lamp bulbs. Looked to see what the circuit is...24VAC thru the heater to a Triac, so AC voltage on this. I thought, not having a 24V lamp, I'd just hang one of my voltmeters across it. Only that voltage spans a range from around 6VAC to around 18VAC, beyond those two ranges is full AC voltage and 0V. For that step in the procedure (Step 11), I set it to where the voltage was near lowest, and NOT turning off.

I was able to get thru the procedure and got it working, though not yet in calibration. For Setting at 500 Deg F, I read around 480 Deg F, at 600 Deg F, I read around 580 Deg F, at 700 Deg F, I read around 660 Deg F, and 850 Deg F, I read around 800 Deg F. In Set Mode, which spans from 340 Deg F thru 875 Deg F, that changes smoothly with the panel control. I'm guessing part of this problem is from not having a flashing lamp to just extinguish, and setting that control at that point (Step 11). Since additional adjustments are being made based at that control setting, it's probably why I'm off.

Just ordered some 24V JKL #2176 lamps with wire leads, 50mA, so 480 ohm lamp resistance across the 13 ohm load has little loading. I'll wait until those parts come in, along with the 50 ohm multiturn trim pots. I had to fake it not having a 50 ohm helipot to add to the test setup to fine-tune test point voltage in Step 4 to 0mV. I was able to get close.

At least I now know I will be able to get this calibrated.....good enough for the time being, and will get better. I looked at my spare EC1201A Iron, finding it has an open Sensor (EC229A), which are a bit expensive to replace. I was able to find Zoro having iron tips (ETC & ETD) for about $5 each, instead of $10-$14 each.