Aoyue 738 4 in 1 solder station power board - Page 1
Forum section: electronics / repair

author: mentholflash
author_rank: Contributor
timestamp: July 27, 2023, 06:29:05 am
content: Hi allHope sumone can help.the heating element failed, so i bought a new one researched how to replace it.I wasn't looking forward to it much but was gonna do it anyway.i powered it up just to make absolutely sure i needed to. (This was my first big mistake)i knew it needed changing.so got all tools together, i started taking out screws and consentrating on instructions from the laptop.I grabbed the old element with a pair of pliers to pull nit out of the handle and bang little puff of smoke it was still plugged in.so 20 years later can anyone help me diagnose and repair the power board just to see if i can get it up and running again.Thanks in advancePhil

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 27, 2023, 08:46:47 am
content: Have you checked the 20mm fuse on the back of the case? The original heating element would have been at mains voltage when you tried to pull it out, which shorted to ground. So the fuse may have popped. Otherwise, something else such as a semiconductor failed. So unless you are willing to check each component, then perhaps you can put this down to experience and just salvage the parts?

author: mentholflash
author_rank: Contributor
timestamp: July 28, 2023, 08:05:42 am
content: Hi mateThanks for the reply the fuse is intact?and yes will be happy to measure all components just dont know what to look for i get ohm's reading on a lot of the board about .56ohmsthanks for ya hep so far matecheers

author: mentholflash
author_rank: Contributor
timestamp: July 28, 2023, 08:07:23 am
content: Hey mate on your avatar it says you are from christmas island?is that truecheers

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 28, 2023, 08:36:13 pm
content: My thoughts if the fuse is ok, suspect the Triacs or their controlling opto isolators.Quote from: mentholflash on July 28, 2023, 08:07:23 amActually, UK based but as we say here, every day is Christmas.This is because we have a political class who treat every day as if it were aPARTAYBut this outside of thevectorscopethat is the EEVBlog.

author: mentholflash
author_rank: Contributor
timestamp: July 29, 2023, 09:00:14 pm
content: Ahh YesNot sorry i left to Sunny Western AustraliaThe ba12 -600b in resistence mode pin 1 to 2 o.lpin 1 to 3 .028 beepohms 1 to 2 o.l pin 1 to 3 43.9ohmsThat is the 1 behind the 4 pin header nxt to blow resistorAlso not sure what a opto isolators isCheers for your help mate

author: eurgenca
author_rank: Regular Contributor
timestamp: July 30, 2023, 04:18:06 pm
content: 1. Replace R12. If no heating or you have a constant heating replace triac BTA12-600.

author: mentholflash
author_rank: Contributor
timestamp: July 31, 2023, 07:47:59 am
content: OkI have a new problem the board is powered but no display and no heatBut its on and tryingcan anyone help furtherThanks

author: wraper
author_rank: Unknown
timestamp: July 31, 2023, 08:13:53 am
content: Quote from: eurgenca on July 30, 2023, 04:18:06 pmI rather suggest checking if triac is shorted before powering anything. Running with shorted triac can easily destroy new heating element in a few seconds, especially when air pump is not running.

author: wraper
author_rank: Unknown
timestamp: July 31, 2023, 08:14:54 am
content: Quote from: mentholflash on July 31, 2023, 07:47:59 amLow voltage part of circuit is powered from transformer. It could be you did not connect it to the board properly. There are 3 identical 4 pin connectors which you could have mixed up. You need to be very cautious about connecting those as one of them is connected to mains voltage (provides power to either hot air heater or air pump). Mixing up can easily destroy things or even cause electrocution.

author: mentholflash
author_rank: Contributor
timestamp: July 31, 2023, 08:56:18 am
content: Thanks for your input mateThere are 3 triacs and 1 regulator from what i can work out But i'm the idiot who did it in the first place So;;tested triac but only have a fluke 73 so only checked for shorts in circuit.No shorts pin 1-2The ba12 -600b in resistence mode pin 1 to 2 o.lpin 1 to 3 .028 beepohms 1 to 2 o.l pin 1 to 3 43.9ohmswires would only just reachAny idea where to go nxtCheers

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 31, 2023, 11:28:41 am
content: It looks like those connectors will just find their way home into the right pin header. Next, methodically test the power rails and check the voltages. I suspect from your first photo there is just one rail providing five volts to that big fat Atmel microcontroller.Beware, the board could be LIVE when connected, so please wear rubber or latex gloves when probing. And make sure you test relative tocircuit groundand not mains NEUTRAL which may have also been traced somewhere on that board. The bare metal heatsinks on the Triacs could also be at mains voltage.Without a circuit diagram, fault finding can be a best guess, based on experienceand electric shocksThe opto-isolator is the white chip - which switches the high voltage Triac using a low voltage GPIO pin . There are possibly two others which are the black six pin chips. Opto-what?https://en.wikipedia.org/wiki/Opto-isolator

author: wraper
author_rank: Unknown
timestamp: July 31, 2023, 12:46:32 pm
content: Quote from: AndyBeez on July 31, 2023, 11:28:41 amWhite optotriac is for 24V soldering iron. 230V heater and pump circuits have black optotriacs.

author: mentholflash
author_rank: Contributor
timestamp: July 31, 2023, 03:19:17 pm
content: Hi allPump runs as soon as extraction or hot air is turned on but no heatas to the optotriac i tested for shorts pi 1 and 2 on all 3 but in circuitDo i need to remove themi was probably going to try triacs next but can only get 1 sort bt137600e in my towncheers guys

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 31, 2023, 08:32:52 pm
content: Quote from: wraper on July 31, 2023, 12:46:32 pmSo what are those two tracks running under the opto isolators doing there? I thought isolation was aphysicallayout thing too?@mentholflash: Maybe post a photo of the underside of the PCB?

author: wraper
author_rank: Unknown
timestamp: July 31, 2023, 08:42:42 pm
content: Quote from: AndyBeez on July 31, 2023, 08:32:52 pmIt's a poor layout which is not surprising as Aoyoe is a low quality Chinese garbage. Not that much better than Yihua, just have been way longer on the market. As station is grounded, creepage distance probably is barely above allowed safety minimum though. BTW creepage distance from white optotriac is about the same, it's just that closest trace is on the left side and resistor on the right side of it rather than trace running under.EDIT: Also you can see that triac circuit with white optotriac is connected to the same connector as rectifier for low voltage power and the distance there is much lower.

author: mentholflash
author_rank: Contributor
timestamp: August 01, 2023, 12:14:28 am
content: The undersideCheers

author: mentholflash
author_rank: Contributor
timestamp: August 01, 2023, 05:30:24 am
content: Hi all trying to test connector for front panel!can anyone tell me where to put com lead from multimeter to measure front panel plug to test for 5v voltageThanks

author: mentholflash
author_rank: Contributor
timestamp: August 01, 2023, 07:06:23 am
content: I measured the voltage while powered from five pin header by the large Atmel from left hand pin of left hand resistorfrom left to right on power board1 2.129v2 2.883v3 2.137v4 2.095v5 2.047vfront pannel 5 pin header opposite right to left1 2.128v2 2.812v3 2.133v4 2.101v5 2.099vif any of that means anythingbut it does mean theres power to the front board so why no displyhas the front board been hit tooThanks all

author: AndyBeez
author_rank: Frequent Contributor
timestamp: August 01, 2023, 08:42:04 am
content: Thanks for the back side photo. Makes more sense when tracing the parts.What is the component part number on the voltage regulator? The matching voltage should appear on the trace feeding out across the board.There is also a big fat power diode 'F' next to that solder bridge/blob. Measure the DC voltage on both sides.

author: mentholflash
author_rank: Contributor
timestamp: August 01, 2023, 12:12:34 pm
content: Would that be on the other heat sinkl7805cv cc02r vw mar 509Cheers

author: AndyBeez
author_rank: Frequent Contributor
timestamp: August 01, 2023, 02:46:02 pm
content: Quote from: mentholflash on August 01, 2023, 12:12:34 pmThat is the 5V linear regulator. Confirm you have 5 volts on the output side.https://components101.com/ics/7805-voltage-regulator-ic-pinout-datasheet

author: mentholflash
author_rank: Contributor
timestamp: August 02, 2023, 03:22:02 pm
content: hey matecouldnt get in there when its inhouse so gonna solder a wire on the leg and try and reach heatsink with the meter pin

author: u666sa
author_rank: Frequent Contributor
timestamp: August 03, 2023, 04:28:25 am
content: There is not much to check and replace here. Besides the obvious big resistor, you have two areas looking crusty-ish.Check all these small resistors.D6 (or D5) looks bad.20 years is time to take the caps off, and check the ESR. Replace all caps with same values bigger voltage, though make sure to check ESR.Check and replace if needed all 4 heat sinked regulators.Check and replace all 3, 8 leggies. You just pull up data sheep and see what voltages should be there.Check and replace all 3, 6 leggies.Make sure your oscillator is oscillating.That's pretty much it.If you not sure what to replace, replace everything. The only thing is to check that new caps are good.Look, on my 2703A+ there was an actual power board in the back and it had two fuses. The controller, here you have something that looks like a controller, that was in the front, was okey. Maybe you have another board in the back, to where power from transformer connects to. Look for board with two fuses on it. If the station shows 89C and temp is not rising, usually it's those fuses.

author: mentholflash
author_rank: Contributor
timestamp: August 03, 2023, 06:04:36 pm
content: Hi allThanks for all your effort so far.i started checking resistors and found the new 1 i put in now measurses short 0.029 continuous beepand other 2 large resistors dont measure at all OLalso R3 reads 0.029 i read them allR22 read at 2.0061 at 1.6395 at 1.132-1.234The rest .279-.710not sure what that means i am cosidering going to the local electronics shop and seeing if i can just re-populate but dont think theyll have everything and the 8 legg and 6leg ic's are missing identificationThanks Again

author: mentholflash
author_rank: Contributor
timestamp: August 04, 2023, 11:27:43 am
content: Hi AllI replaced the voltage regulator and it now shows 5v at the output of the regulatorbut still no displayCheers

author: mentholflash
author_rank: Contributor
timestamp: August 07, 2023, 07:26:00 am
content: Hi allSo i get 5v at the vcc pin and output of v regulator and at least 1 pin going to the displayWhat should i check nextCheers

author: mentholflash
author_rank: Contributor
timestamp: August 15, 2023, 07:14:31 am
content: HiI have remembered what i did a little moreI couldnt get the heating element out of the handle so i pulled the thermo and element with a pair of pliers then it went bangWould this help to narrow my problemCheersI have also been away for a couple of days to the cityI bought 2 bt137f 600 would i be able to swap these out with the bt137 600eThanks

author: wraper
author_rank: Unknown
timestamp: August 15, 2023, 09:30:58 am
content: Quote from: mentholflash on August 15, 2023, 07:14:31 amDo you mean you were removing it while station was connected to the mains voltage? If that's the case, you likely destroyed low voltage electronics by applying mains voltage onto thermocouple. And that was the reason why 7805 died, likely together with MCU and other ICs.