[SOLVED] HAKKO 850 & 850b Hot Air Rework Station - Unable to switch off - Page 1
Forum section: electronics / general

author: LegoLegs
author_rank: Contributor
timestamp: October 09, 2014, 03:35:51 pm
content: I recently obtained 2 x HAKKO rework stations that I would like to repair, however - I am stuck and joined this forum as I was unable to find much information on the web or from support sites. The one unit is a HAKKO 850 and the other a HAKKO 850b.Both units have more or less the same problem - they switch on immediately once connected to a power source. It doesn't matter whether the power switch is in an ON or OFF position. Both the heater and air flow controls still work normally - I can adjust the temperature and airflow without any apparent issues.Has anyone run into this type of issue with HAKKO stations before? Or can anyone help with a suggestion of what could be the issue?Thank you :-)

author: ElektroQuark
author_rank: Unknown
timestamp: October 09, 2014, 03:38:09 pm
content: Reconnect switch leads properly.

author: LegoLegs
author_rank: Contributor
timestamp: October 09, 2014, 03:42:20 pm
content: Quote from: EdoNork on October 09, 2014, 03:38:09 pmThanks, I will give it a try - I do actually have the wiring schematics, they lead me to believe the problem could be with the switch, but in all honesty I did not try to actually remove the leads on the switch and reconnect them....I will give it a try and let you know the outcome - Thank you

author: LegoLegs
author_rank: Contributor
timestamp: October 09, 2014, 04:42:30 pm
content: Quote from: LegoLegs on October 09, 2014, 03:42:20 pmSo I tried the switch leads, but it does not look like there is an issue there. On the HAKKO 850 the switch leads can be removed and reconnected, but on the HAKKO 850b the leads are soldered into place (all tested OK).I did however discover something else - Even though both units switch on immediately when connected to power there is a difference in the way they act depending on the position of the power switch. If the power switch is in ON position all functions work exactly as you would expect, however, if the power switch is in the OFF position the "heater" is OFF and only the pump seems to be running. In short: Power Switch ON = Airflow & Heat / Normal Function. Power Switch OFF = Airflow & NO Heat.On the HAKKO 850b I disconnected the connector from the control PCB that seems to be the power to the "air pump". If I connect the power the air flow LED on the control PCB still lights up (even though Power Switch is OFF), obviously there is no air flow as I disconnected the air pump.Could it be something on the control PCB causing the issue? (Note - I also disconnected the switch without changing anything else and the unit still powered on. Not sure if the reason for that is obvious - I am not an electronics expert :-) If I understand correctly these units have a way off cooling themselves down properly when the power switch is turned OFF (which I assume is controlled by the PCB) and therefore just unplugging mains is not the best way to go.Any other ideas maybe?Thank you :-)

author: ajb
author_rank: Super Contributor
timestamp: October 09, 2014, 08:53:34 pm
content: I would guess the units are designed to keep the pump running after the unit is switched off until the heater drops below a certain temperature to prevent damage to the heating element. In which case, my guess is that something is wrong with the circuitry that does that. Have you confirmed that they properly regulate temperature when running?

author: LegoLegs
author_rank: Contributor
timestamp: October 10, 2014, 06:25:15 am
content: Quote from: ajb on October 09, 2014, 08:53:34 pmYup, the temperature works fine on all settings. I tried HAKKO support directly as well and they just say it is a discontinued model and they cannot offer much support.Interesting is that it is the same issue on both of these units (HAKKO 850 & 850b). I've attached the schematic diagram of the 850b.As mentioned in my reply from yesterday, the unit does power on immediately and the power switch does not turn the unit OFF - BUT, if the power switch is in the OFF position the heater is disabled and only the air pump still runs. Would this not mean that we can still cool the heating element by moving the switch to OFF and then just let the pump run cool air until the unit is cooled down properly? It is not the solution I would want, but I don't want to just write these units off because of this issue

author: nanofrog
author_rank: Super Contributor
timestamp: October 10, 2014, 06:28:00 am
content: Quote from: LegoLegs on October 09, 2014, 04:42:30 pmThis is a safety feature, and is normal.Pump continues to run until the heater is cooled down. Once heater is sufficiently cool, the pump stops running. See page 6 of theHakko 850B manual(bottom of page). Later manuals/product descriptions are more clear about it.For example:Quotefrom the currentFR-802page.

author: LegoLegs
author_rank: Contributor
timestamp: October 10, 2014, 06:34:08 am
content: Quote from: nanofrog on October 10, 2014, 06:28:00 amThanks- That is how I understand as well. The problem is that the pump is always running. If the unit was standing overnight and you connected power it would automatically switch on (regardless of the position of the power switch) - 100F converts to around 38C, I am 100% sure the temperature is much lower than that.It seems like "something" is telling the unit that it is not cooled down and as a result the pump runs constantly. Other than this issue both units work normally.

author: nanofrog
author_rank: Super Contributor
timestamp: October 10, 2014, 06:50:49 am
content: Quote from: LegoLegs on October 10, 2014, 06:34:08 amHow much air is flowing?Manual recommends setting the airflow dial to #8.That said, the overnight aspect however would indicate to me that shutdown isn't functioning (presume you're shutting it down by unplugging it, enough time passes it cools down overnight, and the moment you restore power, the pump starts running).Assuming this is the case, do the temps get to where they're actually set at (thermocouple + dmm or IR thermometer would be handy to verify this) during normal operation?Could point you to the right area (thermocouple section good or not).Unfortunately, I'm not aware of any schematics available, so you'll likely have to trace the circuits out on the PCB's.

author: LegoLegs
author_rank: Contributor
timestamp: October 10, 2014, 07:21:05 am
content: Quote from: nanofrog on October 10, 2014, 06:50:49 amThanks, I've attached the schematics I found so far. I am not an electronics technician so these schematics are not that easy to follow for me. (Also - they are for the North American 120VAC model, the 2 I have would be 220V versions)I did however check the different heat settings and they work fine from what I can see. I did a rudimentary temp. check with a temp. probe on another device and the temperatures change as would expected on each setting, they seem to start around 80C and go up to around 428C.

author: tautech
author_rank: Super Contributor
timestamp: October 10, 2014, 08:25:00 am
content: Quote from: LegoLegs on October 10, 2014, 06:34:08 amIMO this is perfectly normal.My rework station (not Hakko) when plugged in and then mains powered the blower runs at full power (no heat) for about aminuteirrespective of ANY settings.I leave mine plugged in and powered on at the wall switch.If I ever shift it for use elsewhere, it always blows for the 1 minute on power connection , then shuts down.

author: LegoLegs
author_rank: Contributor
timestamp: October 10, 2014, 08:38:04 am
content: Quote from: tautech on October 10, 2014, 08:25:00 amThanks!!!I feel like a complete idiot now - I have not actually tried this... I moved the power switch to OFF and plugged in the mains, as expected the pump came on, but instead of just unplugging it again I let it run for a minute or so and it switched off. When I then moved the switch to ON it came on as usual.The manuals clearly state that it is supposed to run for a bit after you switch it off, but nowhere does it say it would immediately power on if you connect it to mains (obviously if it stays connected to mains you would not have this issue when switching on and off - which is not the case when you are testing a product you are unfamiliar with).Thank you for this answer, now I know that the behaviour on these 2 units is more or less normal.

author: tautech
author_rank: Super Contributor
timestamp: October 10, 2014, 08:51:10 am
content: Checked my manual before I posted and it has no mention of this behavior also.Yes it was a little discerning to me when I got mine, but we know now it is normal.BTW mine is a rebadge, for Jaycar in Aus, a Duratech TS1570.

author: artag
author_rank: Super Contributor
timestamp: October 13, 2014, 07:56:24 pm
content: I have an OKi, it does exactly the same.I assume that it doesn't actually measure the temperature of the heater, it just runs for a fixed delay. Since it can't know whether the heater is hot when it's just been turned on (or, more reasonably, when it's been rapidly turned off and then on again), the safe choice is to always run for the fixed time when first turned on. Note that any temperature measurement will be on the outlet air, rather than the heater itself : that's the point you want to control.The problem it's trying to solve is that the heater will burn out if left running with no air - you should NEVER turn these devices off at the mains when hot : always turn off the panel switches and let it cool down until the pump stops.