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author: blauerscharik
author_rank: Regular Contributor
timestamp: July 18, 2024, 05:13:36 pm
content: Hi Guys,I got this PCB here and did some testing.I am not getting 320VDC on the big cap.That relay KT1 is not clicking through, so I am not getting anything on the bridge rectifier.I got 320VDC on the smaller cap after the small bridge rectifier.Can anyone give me further tips how and what to test?I am assuming the mosfet to the right (L30P70 0B2338SP) might be the issue.Sorry for the pic, I have a subpar phone.Thank you guys in advance.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 18, 2024, 05:14:11 pm
content: The other side of that board.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 18, 2024, 05:19:01 pm
content: Please let me know if the pictures are not good enough.Then I will borrow a different phone and take new ones.Thanks

author: fzabkar
author_rank: Super Contributor
timestamp: July 18, 2024, 05:52:49 pm
content: It's not a MOSFET:https://smdcode.net/uploads/Files/004Tuong/IC/DIP/DIP7/OB2338SP.pdf

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 18, 2024, 06:15:33 pm
content: Quote from: fzabkar on July 18, 2024, 05:52:49 pmThanks.Do you know how I can make sure it works correctly?

author: fzabkar
author_rank: Super Contributor
timestamp: July 18, 2024, 06:22:20 pm
content: It seems to me that OB2338SP generates a 12V supply for the relays. If you can measure 12V at the corresponding test points (eg at various connectors and the relay coils), then this IC must be working properly.I suspect that IC6 is a microcontroller that switches on the relay. This energises the 350V/400V capacitor, and this then supplies the 3-phase inverter (?) under the heatsink. Alternatively, could this IC be a relay driver, eg ULN200x?Is the motor a 3-phase unit?WARNING: Be careful when working on this PCB. It's live.I'm wondering whether IC5 is a DC-DC converter. Perhaps it is responsible for the 5V supply?U1 appears to be a 3-terminal LDO linear regulator.Could IC1 be a dedicated motor controller, or does it do everything?I expect that the PCB will be in standby mode until some switch or key is pressed.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 07:03:28 am
content: Quote from: fzabkar on July 18, 2024, 06:22:20 pmYes that is the issue, I don't get a click and it doesn't get any voltage. I tested the relay with a power supply and it does work.QuoteThat IC6 got the markings "Sonix SN8F570212SG"Under the heat sinks we have six IGBT's "XINER XNM6N60T"QuoteI haven't taken it out yet, but it looks like it. Got 3 wire connection. I added a picture of the nameplate *note the two black wires going to the motor are not present*QuoteI can't figure out the markings on this oneQuoteExactly it's a "SJ 78L05"QuoteLooks like it's for the motor, marking says "RT7075"QuoteThat is also correct, it got another control board with four buttons "power, +, -, and lights"The power button start the fan and + and - you can go through 9 fan stages.And the light button turns on the lights.

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 07:24:26 am
content: If you're not seeing 12V, then examine IC2 and its support components. Check or replace the electrolytic capacitor on the IC's Vdd pin. Also check whether the startup resistor between Vdd and the 320V DC supply is open.RT7075, Richtek, 3 Phase PMSM/BLDC Motor Controller with Gate Driver, 5V & 15V, LQFP-48L:https://www.richtek.com/assets/product_file/RT7075/DS7075-03.pdfSN8F570212SG, Sonix, 8051-based Microcontroller, 1.8 V – 5.5 V, SOP16/TSSOP16:https://wmsc.lcsc.com/wmsc/upload/file/pdf/v2/lcsc/2304140030_SONIX-SN8F570212SG_C337809.pdf

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 07:29:20 am
content: Quote from: fzabkar on July 19, 2024, 07:24:26 amThanks. But they shouldn't be the problem with me not having power at the beginning should they?

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 07:31:02 am
content: Quote from: blauerscharik on July 19, 2024, 07:29:20 amNo, I have edited my post. You were a little too quick with your reply. :-)

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 07:56:06 am
content: QuoteHaHa sorry. I checked the cap right by VDD pin. It seems ok (110nF). I replaced it to test and still nothing.The resistor right by VDD_G pin measures 2k.All other resistors are close to the markings value.

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 08:10:13 am
content: I mean these components.Isn't EC7 (10uf 50V) the VDD capacitor?The startup resistor is actually a string of 3 resistors (125, 205, 125).

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 08:59:14 am
content: Quote from: fzabkar on July 19, 2024, 08:10:13 amIndeed you are right. I took a closer picture.The three resistors have the right value.And the capacitor has 10uf as well.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 03:35:19 pm
content: So is it safe to say that this power switch (IC2) is not working properly?I couldn't find any online to buy...And do I even need it or can I bypass this part of the circuit?

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 04:04:09 pm
content: After you switch of the power, does EC01 retain its 320V voltage? If so, this would suggest that 0B2338SP is not starting.Is there a short on the 5V or 12V supplies? Is the 15V pin of the motor controller shorted to ground?

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 05:14:28 pm
content: Quote from: fzabkar on July 19, 2024, 04:04:09 pmYes it keeps its voltage and slowly drops.No short on 5V, 12V or pin 41 of the motor controller

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 05:35:09 pm
content: Quote from: blauerscharik on July 19, 2024, 05:14:28 pmAs long as the VDD pin is rising above the UVLO threshold (16V), the IC should switch to run mode. If VDD is OK, then the IC is probably faulty.In normal operation the VDD capacitor charges up to 16V via the startup resistors, and the IC then switches to run mode. The IC then pulses its MOSFET chopper. The auxiliary winding on the transformer then supplements the VDD supply via the rectifier diode and takes over from the startup resistor.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 19, 2024, 05:46:02 pm
content: QuoteI don't have a steady voltage on the VDD cap. It jumps around 9V, 10V, 12V 15V an back to 9V.

author: fzabkar
author_rank: Super Contributor
timestamp: July 19, 2024, 05:59:56 pm
content: Quote from: blauerscharik on July 19, 2024, 05:46:02 pmThat would suggest that the IC is trying to start. It is pulsing the MOSFET, but the auxiliary winding is not replenishing the lost charge in the VDD capacitor. Every pulse reduces the charge until VDD falls below 8V, at which point the IC switches from run mode back to start mode. The capacitor then recharges to 16V via the startup resistor and the cycle repeats.In other words, your supply is hiccuping. This is most often due to an overload on the secondary side, or a bad VDD capacitor (high ESR). I would hardwire a second capacitor in parallel with the 10uF cap and see whether this resolves the problem.Edit:Is the 2R2 sense resistor OK?Is the primary winding of the transformer OK, ie not open circuit?Here is a source for the IC:https://www.lcsc.com/product-detail/Switching-Controllers_OB-On-Bright-Elec-OB2338SP-H_C507634.html

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 20, 2024, 07:29:59 am
content: QuoteI tried a new cap 50V 22uF (the smallest I had on hand). Same issue.I took out the transformer the windings are fine.The 2R2 resistor shows 2.1ohms so that's fine.Can I not just bypass this circuit altogether so it's always on?

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 20, 2024, 07:38:01 am
content: QuoteNice thanks. It's on backorder though.

author: fzabkar
author_rank: Super Contributor
timestamp: July 20, 2024, 09:56:51 pm
content: The IC appears to be available through various sources on Aliexpress. I don't know how many can be trusted, though.As for bypassing this supply, I would first want to know how the 12V supply for the relays and the 15V (?) supply for the motor controller are generated.

author: blauerscharik
author_rank: Regular Contributor
timestamp: July 21, 2024, 04:42:03 pm
content: Quote from: fzabkar on July 20, 2024, 09:56:51 pmGiven the hassle it would be to source this part and try and test it and then find out they are not good enough I will consider this as not fixable.Now it just comes down to pure entertainment and educational aspect for myself.