Graphite grinder 900W [59G187] Not turning on - mysteriuos 501b-8P IC - Page 1
Forum section: electronics / repair

author: HiddenBear
author_rank: Newbie
timestamp: January 12, 2025, 07:56:46 pm
content: Hello Fellow EEVblog ColleaguesAs in the title I have a problem with a grinder that have a regulated rotory setings (via a potenciometer). The grinder is not working at all. The thinks I checked :- Brusches (because it's a brush one) | Maybe a half on them is left, but the contact to the rotor is there. No cracks oraz lose wire, only normal sights of wear.- Cable | few ohm, so its fine- Switch | All contacts work well, no leacked or burned pins- All components on the PCB that i know how to measure : R, C ,D show correct values. I dind't measured the ESR of the caps because I don't have the equipment for that.- The triac have a 0.056V drop between A1(+ multimeter wire) and Gate(- multimeter wire) as well Gate to A1, the voltage drop is the same. Changed it for a BTA 12 that has 0.112V dropThe triac replacement didn't help. And there is that 501B-8P IC, I have no clue that this thing is my brain is too smooth to figure it out by it's own. I tried to check on AllDataSheet but didn't find it with the same 214DNWG0a e3 or similar ending. The rotor moves with easy so it's not blocked or jammed.Below I inclued the worst electronic schematic in my whole history, and photos of the board front and rear.One think that I could discover was that the R1 20k resistor heats quite quickly after some 3-4 sec of pressing the switch trying to power on the grinder.If someone had a similar problem maybe not exacly with the same grinder, but a similar issue with a module like that. I'd be thankful for helping to solve with this problem.

author: fzabkar
author_rank: Super Contributor
timestamp: January 13, 2025, 02:24:31 am
content: I'm guessing it could be a Sonix SN8P501B-8P (OTP micro?).

author: inse
author_rank: Super Contributor
timestamp: January 13, 2025, 04:16:57 am
content: Is there supply voltage across the electrolytic cap?If not, isolate the IC supply pin.What is connected to the white cables, some speed feedback from the motor?P.S. I agree on the schematic ;-)

author: fzabkar
author_rank: Super Contributor
timestamp: January 13, 2025, 05:11:11 am
content: The circuit diagram would be a little less confusing if the pin numbering could be corrected.Perhaps the IC is similar to this (SN8P25011DP)?https://wmsc.lcsc.com/wmsc/upload/file/pdf/v2/lcsc/2304140030_SONIX-SN8P2501DPB_C337779.pdf(page 8.)

author: HiddenBear
author_rank: Newbie
timestamp: January 13, 2025, 03:59:55 pm
content: I agree with You fzabkar and inse that the diagram could be better made my me. I forgot to mention that the pin names on the IC are taken from a NE555, because it was the easiest to implement in KiCad. That could straighten few thinks in advansed, my bad.I check the cap as recommended and the voltage is there. So I'm assuming that the IC just broke.I found today that on Aliexpress there is a 501B-8P but with 1464NSZ01 e3 ending, not the same that is on the PCB.Link to that :https://pl.aliexpress.com/item/1005008067801762.html?spm=a2g0o.productlist.main.1.67e71d3clccl2W&algo_pvid=7ce4e9b6-265f-41e9-a15f-2d58fb15fad9&algo_exp_id=7ce4e9b6-265f-41e9-a15f-2d58fb15fad9-0&pdp_npi=4%40dis%21PLN%211.97%211.93%21%21%210.46%210.45%21%40210385db17367819171196180e291f%2112000043523675103%21sea%21PL%210%21ABX&curPageLogUid=Ka0z9LlojdAG&utparam-url=scene%3Asearch%7Cquery_from%3AGonna give it a try, maybe it will work. Will give a replay in this post about how it worked out or not.But to be honest I'm still courious what that IC actuall is, because the whole regulator look like a triac dimmer with the adition of the IC (Schematic not made by me). I even builded one for a 3-phase low power USSR wentilator converted to a 1-phase, and it's working quite well (without the IC of course). Checked the PDF link and I'm not sure if it would be a microcontroler unit, seems a bit to expensive for a grinder to me. Maybe it's a circuit that prevents the engine to stop then the grinder is in lowest rotations around ~800 revolutions per minute. Welp, without the schematic we don't gonna know.

author: fzabkar
author_rank: Super Contributor
timestamp: January 13, 2025, 08:05:39 pm
content: I suspect that the second line reflects the unique OTP firmware. Even if you received a blank MCU, you would then need to program it.

author: HiddenBear
author_rank: Newbie
timestamp: January 13, 2025, 10:10:25 pm
content: Ou, that think I did not consider at all. The cost of shiping and the IC itself is not that high anyways. Gonna try if for pure science with the hope that it will work then xD It'll be still cheaper to test such metod than buying a new grinder. Maybe it will work, only field testing will it proff.