Hakko FX-888 or Aoyue 937?

[ptricks]

No presets on mine either, but not really an issue for me .
Not long after my posting I turned on my aoyue 937 and got an error message on the display. I pulled out the meter, checked the pins on the irons cable plug and sure enough one of them was open that connects to the iron. I disassembled the irons heater and pulled out the cable and found the heating element had gone bad, no surprise it has been a really long time since I bought it. It came with a spare but in my moment of impatience to get it working again, I was working on repairing an oscilloscope and just had to get it done, I didn't pay attention to the color of the wires, so when I installed the new heating element I accidentally connected the heater+sensor wires to the element and another pair, heater+sensor to the temp sensor. There are only 5 wires and the 5th is a ground.

I turned on the station and for a second it displayed  200 , then a loud pop and smoke from the station. I quickly pulled the power cord. After cussing for a few minutes I took the station controller apart.  The boards controller chip is a atmel 8051 part. The board has a JRC ADC , and for the temp sensor uses an lm358 op amp. The 8051 feeds a control signal to a fet  that controls the power to the element.  Display digits use a simple 74xxxx driver, Iwas worried I had blown the 8051, it ran code stored in its internal flash, and I had no copy of the firmware.

The part that popped turned out to be  a cap, 10V, 47uf connected to the temp sensor. I guess when I wired wrong it got fed 24VDC and it couldn't take it. I found a replacement and soldered it , flipped the power switch and saw 200 on the display, the iron was getting hot and so I tried increasing the heat to 350. The iron got hotter and hotter but the temp now read 000 and wouldn't increase. I figured I must have killed the ADC or the Lm358 or maybe a port on the 8051. I measured all the chips and support electronics and couldn't find anything wrong.  In a last ditch attempt I thought that maybe the electrolyte from the cap leakage might be the problem so I scrubbed the board down really well. Flipped the switch again , and it worked !

I have to give credit to aoyue on the design. The pc board has all the component values silk screened so even if the part is utterly destroyed like this cap was you can still figure out what to replace it with.  The parts are pretty generic so no problems there either. Only catch might be the firmware on the chip. If I get a chance I plan to dump the firmware for a backup. Someone more familiar with the 8051 could probably add custom code fairly easily.

[ablacon64]

Nice, I like that! I like to be able to fix my tools if I have too, point to Aoyue! I have some YaXun that also does not remember the last setting, but that's not really a problem. Presets are nice if you work with different boards and different kinds of solder.

[nanofrog]

Presets are nice if you work with different boards and different kinds of solder.

Nice for connectors too IMHO. 

[Psi]

There's nothing wrong with Aoyue but Hakko is a higher quality brand.

[T4P]

Good if you can ONLY get a real hakko at very inflated prices compared to the west. You guys have it good there  200 bucks for the FX-888 GOSH!

[tlu]

Ptricks, with only 45W I assume the Aoyue would not be able to do lead-free solder as easily as the Hakko? That was my main concern while choosing between the two. I ended up with the Hakko FX-888 for its built quality and reputation.

I do use an Aoyue 952D+ reflow station and it quite good. Not have a hiccup with it yet. So when came time for a decent iron I had to choose between the Aoyue 937 and Hakko FX-888 and the deciding factor was output power. For me 70W vs 45W was an easy choice.

[IanB]

Ptricks, with only 45W I assume the Aoyue would not be able to do lead-free solder as easily as the Hakko? That was my main concern while choosing between the two. I ended up with the Hakko FX-888 for its built quality and reputation.

I do use an Aoyue 952D+ reflow station and it quite good. Not have a hiccup with it yet. So when came time for a decent iron I had to choose between the Aoyue 937 and Hakko FX-888 and the deciding factor was output power. For me 70W vs 45W was an easy choice.

You made a good choice in picking the Hakko, but do not confuse power with temperature. Power concerns how big a work piece you can solder, while temperature concerns when different kinds of solder melt. A low power iron could do high temperatures, and a high power iron might only do lower temperatures. (Consider for example a typical clothes iron. It has a power of maybe 1000 W but even so it will not melt solder if it is working properly. On other hand a small 25 W soldering iron can melt solder easily.)

By analogy with electricity you could think of temperature as voltage and heating power as current.

An important quality measure in a soldering iron is how well it can control and regulate the tip temperature. High quality irons do this much better than low quality irons. A good iron would be like a regulated power supply, while a cheap iron might behave like an unregulated supply.

[tlu]

IanB, very well put. I was alluding to that point but did not know quite how to explain it. You said basically what I intended to say.

I'm quite satisfied with the Hakko FX-888 and for $69.99 + tax at Fry's Electronics in the states, it was a really good deal.