Aoyue 937+ soldering station woes

[nato]

Hi,

I've had an Aoyue 937+ soldering station for a bit over a year now. I've probably only used it about 5 times, for perhaps an hour each time, but now it doesn't work. The symptoms are:

1. The indicated temperature rises much more slowly than it did when I first received the unit.
2. It takes *much* longer to melt a solder joint than it did when I first received the unit. This occurs even when the indicated temperature is at a reasonable temperature for soldering.

Has anybody experienced these symptoms with a soldering station (not just an Aoyue)? I've read through the troubleshooting guide within the included manual and nothing seems to fit the symptoms that I have.
http://www.ludatronics.com.au/aoyue_937_937+.pdf

Here's what I've tried so far:

Even though the tip is very clean, I've replaced the tip a couple of times with no improvements in the results.

I've also made certain that the nuts holding the handle together were tightened well.

As directed by the manual, I've taken measurements of the resistance of the handle. These measurements seemed to be within the manual's specifications. Even so, I knew of nothing else to try, so I replaced the heating element.

The new heating element has resistance values that are very similar to the original's. Replacing the heating element did not fix the problem. For those who are curious, the following are the measurements of the handle:

Between pins 1 and 2 (heating element): 19.7 ohms (manual specifies 18-23)
Between pins 4 and 5 (heat sensor): 1.2 ohms at room temperature. This is outside the specified range of 2.5-3.5, but turning the iron on for a few seconds, removing power and testing gave an initial value of 5.6 ohms, and it dropped back down through the specified range and to the 1.2 ohms within a few minutes. I believe that this indicates the temperature sensor is working properly and wouldn't produce the symptoms that I'm having.
Between pin 3 and the tip: 0.1 ohms (manual specifies below 2)
Between pins 4 and 2: No continuity (as specified by the manual)
Between pins 4 and 1: No continuity (as specified by the manual)
Between pins 5 and 1: No continuity (as specified by the manual)
Between pins 5 and 2: No continuity (as specified by the manual)

All of these values are within the ranges specified by the instruction manual.

I've contacted the manufacture asking for clues on what the issue might be, but after an initial round of questions of where and when I bought it, I haven't received any response.

I can't seem to find any other possible solutions to attempt to fix my station in the manual or elsewhere online, and I'd really hate to have to throw out this station after so little use. I have found that I can purchase a replacement handle, but with nothing suggesting the handle is bad, I don't want to go throwing good money after bad.

Do you have any suggestions on what I should try or test next?

Thanks for reading!
Nathan

[Agent24]

If the iron checks out fine then it's likely the controller board which is faulty, or perhaps a bad connection on the base station.

If the board is faulty, it can probably be repaired for pretty cheap - IF you can find what's wrong with it.

Without a schematic or a working unit to compare voltages etc that may be rather difficult.

[nato]

Thanks for your reply Agent24.

So I guess my somewhat uneducated hunch is that the problem *might* be the handle itself. A mechanical problem with the iron, not an electrical problem since all of the continuity measurements seem to be consistent with the manufacture's specs. Perhaps for some reason the heat isn't being transferred from the element to the tip efficiently.

In my mind that seems to be consistent with the symptoms.

Does a controller board problem seem consistent with the symptoms?

1. The indicated temperature rises much more slowly than it did when I first received the unit.
2. It takes *much* longer to melt a solder joint than it did when I first received the unit. This occurs even when the indicated temperature is at a reasonable temperature for soldering.

Maybe the first one, but the second one along with the first?

Also, if anybody thinks there might be a more effective source or even a different forum for help on this, I'd appreciate any other suggestions too.

Thanks again for reading, and your help,
Nathan

[Agent24]

I have a 936 but I believe the irons are basically the same, just yours has digital control where mine is analog.

I'm no expert either but this is what I think:

1) It should be immediately obvious if the element wasn't making contact with the tip properly or there was some other mechanical problem. likely there would be something physically broken, or not fitting together right\loose etc, or a huge buildup of dirt\oxide.

Since you replaced the tip, that's not likely the problem, and since you replaced the element, that should be OK too.


2) On mine, the temperature sensor is part of the element. This means the temperature can only be incorrect if the element\sensor is broken. It doesn't matter what the tip is doing since the sensor is not actually in the tip.

Since you replaced the element and checked the continuity\resistance, it would appear the element and sensor are OK.

This does leave a question of the iron's cable and plug though. If your tests are OK then that assumes the cable is OK, but it may have intermittent connections to the heater which fail under the higher current needed for the heater. (your tester will be using nowhere near the same amount)


If the cable and plug is OK though, then that logically leaves something at the base station, anywhere from the socket on the front to the controller board inside.

Unfortunately I can't really help after that. You could check the socket for a faulty\dirty connection but if that's OK then it's where it gets tricky.

I would help and let you compare things on my station, except I don't have the same one.


If you're interested in trying a different forum, though, I suggest the one at badcaps.net

Post your question in the 'Test equipment' section (that's where most everyone else posts about soldering irons, even though they're not test equipment)