[Solved] Hakko 850 Rework station - power switch wiring help - Page 1
Forum section: electronics / repair

author: Exxor
author_rank: Contributor
timestamp: May 03, 2024, 05:00:25 am
content: Hi everyone, I finally joined eevblog after years of perusing all of the great content on here.I have a Hakko 850 that looks like someone tried to repair but they were in over their head. Besides all of the components I had to replace, I believe the power switch wires are connected incorrectly. Is there anyone on the forum that has a 850 schematic (I could only find 850B and D schematics are they are not similar enough)? If no schematic, is there anyone here with an 850 that wouldn't mind cracking it open and just telling me which pins on the power switch route to which pins on connector VH5?Huge thanks in advance,Exxor

author: alanep
author_rank: Contributor
timestamp: May 03, 2024, 12:07:55 pm
content: Hello Exxor,I don't have the schematic but I did check out my Hakko 850. I disconnected VH5 & took a photo. The pins are actually numbered on the white connector case as per the numbering in the photo. I buzzed them out to the front power switch. Because the switch NC/NO contacts could interfere with the buzzing out, I temporarily disconnected the wires from the switch (to be sure).The numbering shown in the switch photo are their corresponding VH5 pins.A few other notes:VH5 pin 4 goes to the fuse holder. VH5 pin 5 isn't used.The power switch LHS has wires going elsewhere - I didn't check them out as you only wanted those specific to connector VH5.I hope this helps.

author: Exxor
author_rank: Contributor
timestamp: May 03, 2024, 01:33:27 pm
content: Wow, I cannot thank you enough. Your wiring corresponds to exactly how I suspected the board layout dictated. The prior "tech" had mis-wired it!Also interesting to note that compared to your board revision, those 27K resistors are 12K ohm 5W jobbies. The board is discolored under them, so it appears they are working hard.Thanks again!

author: alanep
author_rank: Contributor
timestamp: May 04, 2024, 06:51:48 am
content: That's really good news.Re the 850's 27K (mine) vs 12K (yours) resistors, it might be that mine is a 240V unit. Is yours 115V? Although this thread is about the 850 (no schematic), the 850B schematic (readily available online) shows two resistors R14, R15 (15K 3w) which might have a similar function to those on the 850. They are voltage dropping resistors for IC1's (upc1701C) power supply from the mains (no transformer). I haven't shown the 850B schematic to avoid confusion.It wouldn't be too hard to reverse engineer the PCB of the 850. It only gets occasional use (hobbyist) & it's been very reliable (bought in late 1993) such that I never had to do so.

author: Exxor
author_rank: Contributor
timestamp: May 05, 2024, 01:19:51 am
content: Quote from: alanep on May 04, 2024, 06:51:48 amYou are exactly right. My board is 120V. I do have a copy of the 850B schematic, as it shares a lot of the same design so I figured it would be good to have around so long as I can't locate a 850 specific schematic. Thanks for helping to save this little rework station's life!

author: alanep
author_rank: Contributor
timestamp: February 15, 2025, 03:24:11 am
content: For those interested in this dinosaur, I recently had to investigate a fault with the Hakko 850. Whilst the Hakko 850B schematic is available on the net, I couldn't find any schematic specific to the Hakko 850. So, using my unit, I reverse engineered the schematic & hand drew the component overlay (apologies for the quality). The Hakko 850 doesn't have any closed loop temperature control, just duty cycle control.Note this is for the Australian 240V version so some of the component values maybe different to other regions.Schematic V1.3 amends R4 connections & shows earth wire to handle.

author: Exxor
author_rank: Contributor
timestamp: February 17, 2025, 02:28:05 am
content: Nice work, thank you!