Yihua 936 burning resistors - Page 1
Forum section: electronics / repair

author: algorithm
author_rank: Regular Contributor
timestamp: March 08, 2021, 04:10:38 pm
content: So a while back my yihua hakko knockoff stopped working. Took it apart to find r1 and r2 burnt beyond recognition. After research i believed r1 and r2 were 330Ω and 150Ω respectively. Replaced but then they went up in smoke too. Read someone on here claim the triac was the cause. Replaced the bt137 600e, r1 and r2. Smoked again. After testing diodes and resistors to find them all good, the only thing i neglected was the lm358. Found a spare on an old board and swapped them, as well as the resistors. Powered on, now that stopped the resistors burning i think, but now the heating led no longer lights. Found if i bridge the t1 pin of bt137 to heatsink (t2 pin i think connects to the mount plate?) the led lights and it heats... The transformer is outputting 32v yet the label boasts 24v. 32v ac*Really unsure what im missing or why ive struggled so much with such a simple circuit. Anybody got ideas on what i should look at or try? Thanks in advance.I worry that the triac replacements i got were bad. Because before replacing the triac the led did light, but failing to dim. The bt137 i originally took off read from t1 to g at 400Ω, while the replacements i got all read 1.2kΩ. What do you think? Lol thanks again, any help truly is appreciatedBtw isnt it an enigmatic curiousity to solder a soldering iron? Lol

author: Refrigerator
author_rank: Super Contributor
timestamp: March 08, 2021, 05:32:05 pm
content: Is there a schematic of your soldering station?Personally i'd suggest to switch over to T12 based soldering stations, the tips are so much better and easier to change and stations are quite good also.

author: tunk
author_rank: Super Contributor
timestamp: March 08, 2021, 06:04:33 pm
content: Looks like you can find controller boards from around 5us$on ebay, aliexpress etc. And are you sure your element andtransformer are ok?

author: algorithm
author_rank: Regular Contributor
timestamp: March 08, 2021, 07:50:02 pm
content: Pretty sure the element and transformer are alright, although it outputting 32v ac might be too much? Not sure. The sticker says 24v. The opamp max v is 32v iirc. But would that be dc? LolI dont know of an exact schematic, guess its a clone of this though?https://www.slideshare.net/tarzan1a/hakko-936-gorsak-952-diy-analog-soldering-station-schematic

author: amyk
author_rank: Super Contributor
timestamp: March 09, 2021, 01:08:15 am
content: Post pictures of the board (both sides), not hard to draw the schematic from it.

author: algorithm
author_rank: Regular Contributor
timestamp: March 09, 2021, 04:01:31 am
content: Sorry amyk. I wish i was better than i am lol. Well ive given up on repairing this to its original glory. Although i wonder if someone could explain how the heating works?I started thinking what if i just feed the transformer to the 2 heating pins? Then id have a station always full blast right?EDIT: i found out that yes it will be full blast if you directly connect the transformer to the irons element pins. Better than it entirely going to waste. Not sure of anything better to do with that transformer anyway. Just a spare iron. Thanks for the replies.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 10, 2021, 08:37:30 pm
content: Quote from: algorithm on March 09, 2021, 04:01:31 amIt might melt down, at least mine almost did when i let it go full tilt for a few seconds.And i don't mean literally melt down but it might get smelly and smokey. Also the transformer might not like it.You can get a T12 station for 20 bucks so i'd suggest upgrading, i might be sounding like a broken record but it's just that much better.I've had both stations and after using T12 for years you would have to drag me kicking and screaming back to these 936 clones.

author: RayRay
author_rank: Frequent Contributor
timestamp: March 11, 2021, 02:23:35 am
content: I know this is the repair section and all, but in my honest opinion, those 936 knockoff stations are garbage, and aren't worth fixing! On the original 936, the heating element & original tips match up (very little spacing between the heating element & inner portion of the tips, contirbuting to excellent heat transfer) whereas on the knockoffs, the diameter of the heating element & inner portion of the tips vary drastically (contribuing to poor heat transfer) so in terms of usability, it sucks hard (I used to have one of those!) my advice, spend $40 on a T12 based soldering station from Aliexpress (it'd be an excellent investment & a huge improvement!) be sure to buy some extra tips too. You'd thank me later, trust me. There's no room for comparison really.Edit: Also, you might wanna get a FG-100 replica, for temperature calibiration.