I just bought some spare 888D soldering stations, (the lure of the recurring Fry's sale) and having read all about the latest and greatest irons in these threads, I wonder if I should have not just bought an FX951 or even fooled around with a (gasp) Bakon950D 75W iron (which is apparently the latest rage in Russia, if you go by the youtube videos, lol). Did I just lock myself into an inferior iron for the next 5 decades? So I decided to see if the Hakko 888 lives up to its power rating of 70W that is printed on the bottom.
The voltage is stated to be 26V.
My true RMS fluke is... somewhere. So I put my scope to the transformer 26V secondary to see what was happening. In fact, the voltage was very stable, even when the heater was cold (which makes the resistance only 3.2ish ohms). It started out at 90.x V pk to pk. And after perhaps the transformer warmed up a little, it settled to... 88.8V. I expected when the heater was on that the voltage would sag. But this voltage remained completely stable whether the heater was on or off!*
Pk to pk voltage of 88.8 x0.5/1.7 =26.12V rms. Rounded down for measurement error of my scope, it is hitting the mark.
So then I set about measuring the temp of the heater at temp. I figure the average soldering temp is about 350C. So I heated up the iron to 360C for good measure, unplugged it, and I immediately got the DMM probes onto it as fast as humanly possible. And I got... 8.8 ohms.
26V squared / 8.8 ohms = 77W. It looks to me that Hakko is not overstating the specs, at all.
The Bakon runs at 19V. I am not sure what the resistance of the heater is, AT TEMP, but it is said to be around 2 ohms, cold. If we were to extrapolate, let's just say it might be around 2 x 8.8/3.2 = 5.5 ohms ... for a nominal 65.6W. This isn't taking into account the pauses to read the temp sensor, either, which appears to be fairly significant. Probably something like 5% of the duty cycle.
I found this vid, and I am fairly satisfied with my decision.
https://youtu.be/fq439J4ZbrY?t=125Love that warm up speed on the display. Not so great on the actual melting of solder, though. This is actually pretty close to the same speed as 888, which has higher thermal mass tip. And a much better stand.
*I haven't looked too hard at the pcb, and I don't know if there is a public schematic. But there is a large power resistor at the top of the board. I am guessing it might be a dummy load for keeping the transformer output so stable. I might clip this and see what happens.... A little faster cold start time and less power consumption, perhaps? The triac is rated for 600 V, so the longevity of the heater would be the only concern, I think. Well, I suppose I should check all the caps in case they're cutting it close. I'm fairly impressed at the beefiness of the transformer, though. From a cold start it is pumping around 8 amps without any sweat, although I admit I missed the first 5 seconds, while fiddling with my scope voltage scaling and switching from DC to AC... noob mistake.