Aifen A9e (A9 Pro?) Grounding Issues - Page 1
Forum section: electronics / general

author: Basileus
author_rank: Regular Contributor
timestamp: July 04, 2025, 08:21:31 pm
content: Hello, I bought an Aifen A9e soldering station a couple of months ago, i had done a quick continuity check between the tip of the iron and the earth ground connection on the C17 socket in the back of the unit and it seemed fine, about 0.49 ohms, so i had assumed the station didnt have any issues; recently though, user ftg posteda couple of videos and oscilloscope screenshotswhere indeed there's seems to be spurious voltage on the tip that might lead to damage to sensitive components.I decided to open the unit in the hope it would be similar to the A9 version (which user thm_w seems to have easily fixed inthisthread), but no dice: the unit uses a different pcb which is not quite similar to the A9 one. Silkscreen says "A9 Pro", so i assume A9 pro and A9e use the same control pcb.I can't make much sense of the situation, from the pcb all i can tell is that the earth ground connection is routed is a rather unusual way, branching through capacitor C3 and component T1 (which looks like a resistor, but why would it have T as reference designator?). I haven't attempted any physical modification yet. If anybody has a clue on what might be at play and how to fix it it would be amazing, I would like to know the opinion of other more knowledgeable A9e owners.

author: thm_w
author_rank: Super Contributor
timestamp: July 04, 2025, 10:58:32 pm
content: T1 looks like a resettable thermal fuse.If C3 is in series with earth lead then it doesn't make sense that its 0.5 ohm from IEC inlet to the tip. Unless there is a connection somewhere else to the tip.If T1 is in series then you could get some voltage drop across that.Did you verify the IEC cable that came with the iron has a working earth lead? (just in case).It might be necessary to run your own wire from earth to the connector for the iron tip (CON2?) just to bypass all of that.

author: Basileus
author_rank: Regular Contributor
timestamp: July 05, 2025, 04:08:51 am
content: Quote from: thm_w on July 04, 2025, 10:58:32 pmOh yes good pointQuote from: thm_w on July 04, 2025, 10:58:32 pmNo, it's not in series, from the looks of it C3 and T1 have one side connected together on the IEC socket side, and the other going to different paths being connected to different copper pours. Dotted lines are my assumptions.PCB:Both sides of C3 have low impedance to the earth connection so i suppose they might be in parallel, though i find the setup quite strange. The matte black solder mask, the many buttons and screen going over traces and the fact its all very low impedance makes it pretty difficult to understand the path.Quote from: thm_w on July 04, 2025, 10:58:32 pmNo, but i haven't been using the one from the station but from my Rigol oscilloscope, so i assume it's good.Quote from: thm_w on July 04, 2025, 10:58:32 pmThe power related connections of the iron are on CON7, the largest 4 pin connector in the bottom right of the board. I could run a wire on the back from the earth lead connection to pin 2 (GND) of CON7, but i'm hesitant because i think its clear they are keeping the connection very separate from the rest of the ground pours on the pcb.Despite having a GND pour on the back right next to CON7 GND on the back of the board, i think the path goes down under the TEMP+ button, changes layer, goes through the shunt looking resistor R34, and only then goes to the GND of CON4 (PSU connector). Is it possible R34 is being used to monitor current through the iron cartridge?

author: thm_w
author_rank: Super Contributor
timestamp: July 07, 2025, 09:53:30 pm
content: R34 would be current shunt yeahYou wouldn't be bypassing that and don't want to, the earth ground and solder ground should be separate everywhere except where that green wire is tacked onto the board.So you'd just provide a lower impedance connection instead of having it run on the board through T1. Which I guess is a 0.5A SRF if it looks like this form the side:https://www.aliexpress.com/item/1005005816556049.htmlAssuming that is the issue..The fuse itself has a resistance around 0.3-0.5 ohms.

author: Basileus
author_rank: Regular Contributor
timestamp: July 07, 2025, 10:50:58 pm
content: Quote from: thm_w on July 07, 2025, 09:53:30 pmOh yea that's substantial. Just replacing the fuse with a solder blob might make make a substantial difference then. But are you suggesting to change the position of the earth lead from its position to the back of GND Pin 2 of CON7 directly?

author: thm_w
author_rank: Super Contributor
timestamp: July 07, 2025, 11:24:23 pm
content: Quote from: Basileus on July 07, 2025, 10:50:58 pmOr add another wire, yeah one of the two.You can try bridging the fuse if you don't want to do that.

author: Basileus
author_rank: Regular Contributor
timestamp: July 22, 2025, 02:21:50 pm
content: Quote from: thm_w on July 07, 2025, 11:24:23 pmTried soldering the earth ground connection to the back of CON7, unfortunately that did basically nothing: station will still blink a red led if its connected to earth ground.I would have done oscilloscopes measurements if the voltage leak wouldnt have lit an led, but i would say at this point it doesnt make sense. I'll revert the earth ground connection as it was.Down here i'll post my measurements BEFORE the attempted fix. I referenced the measurement setup illustrated in IPC-TM-650https://www.electronics.org/sites/default/files/test_methods_docs/2.5.33.2.pdf,setup as figure one minus the metal box and ac filtering. Results are similar to those done by user ftg.Setup:Measurements:And with averaging sampling mode:I don't think there's much else to be done. Guess it's time to ponder whether its a problem for my workflow and whether i would be served better with a GEEBOON station (maybe even just the base TC22, if their claims are legit). Kinda annoying because my older Queecoo T12-955 does not have voltage leak issues, not at this extent at the very least.