| Electronics > Repair |
| Aston Martin DB9 rear light LED driver repair.......... FIXED!!! |
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| cpposteve:
Hi all. I was given by my uncle he DB9 rear light and asked if I can repair it. Given I have repaired a few automotive board, one being my body control ecu on my Alfa, I thought yea ok no worries. It’s only an LED driver board, how hard can it be..!! My bad..!!! Pictures are below for reference. I will try and describe the best I can to help understand the issue. The top part of the light has two sets of leds. One long set and one short set. The short set AND long set come on when the lights are on. But only had say 50% brightness. You can see that’s it’s being pulse width modulated when you record it and play it back. Also given the ic’s being used inside but I will go more into that later. Then when the brake light it pushed while the lights are on the short strip lights up full brightness while leaving the long strip at 50% brightness. I know this from watching the other working light on his car. Now there are 5 wires on the back of the controller. 1. Neg 2. Brake 3. Lights 4. Indicators 5. Fog light. Now I’ve checked the voltage going to the connector when plugged into the car and each input is just seeing a strait 12v. And nothing comes up on the dash as a fault light to say the lights are out. Eliminating the possibility that it’s canbus controlled. The issue with these lights are when you put 12v to the light on brake nothing happens. Just draws 67ma. If I put 12v on the lights input the brake part lights up dimly and flickers badly. But the other part does not light up as it should. I have replaced the 4x ti ucc2813d-3 Also replaced 2x st mc33079dt I have reflowed all components, checked all Mosfets and diodes, capacitors. But can not find any dodgy components anywhere. Used the microscope to check the tracks. Even tested most of them for continuity. Spent over 10 hours on this now. And begining to runout of ideas on what to test not. I’ve read the data sheet on the ucc2813d-3 which is very full on. And understand it to a degree. Checked all supporting components and their values and all ok. But the ucc2813d-3 will not put out and pwm signal to the mosfets that drive the leds. The data sheet is limited on what to check. This is where I’m up to. Trying to find out why it’s not outputting a pwm to the driver mosfets. Is the ucc2813d-3 in a fault condition? How do I tell? Any help would be much appreciated. Cheers. Steve |
| tunk:
I have no idea what the problem is, but here's a couple of things you may already have tried: - switch the clusters to rule out cable problems. - switch the PCBs to confirm that it's a PCB problem. The PCB may also possibly be used in other (cheaper) cars. |
| cpposteve:
Cheers Haven’t tried what’s on your list. Swapping the boards would be a right pig of a job. As the lights are glued shut and the other one is working. So not really a good idea but may have to if all else fails. I will swap the lights over to check cables though. Cheers |
| fzabkar:
ISTM that the UCC2813 PWM controllers are operating in open loop mode with the FB pin as the control pin. That is, the chip outputs a PWM signal with a duty cycle determined by the DC voltage on its FB pin. If the voltage at FB is less than REF/2 (Vref = 4V), then the output is switched off. I would determine which chip is driving the FB pin and work backwards from there. http://www.ti.com/lit/ds/symlink/ucc2813-0.pdf https://www.st.com/resource/en/datasheet/mc33079.pdf I'm assuming that you have used an LM324 as a substitute for the MC33079. |
| Zucca:
your last picture shows a corroded PCB, the one you attached shows an immacutale board, I'm confused. Did the light suffered any water ingress? You need to get your hands on the known working board and with a scope point to point check back and forth. --- Quote from: cpposteve on July 16, 2019, 11:51:28 am ---Now I’ve checked the voltage going to the connector when plugged into the car and each input is just seeing a strait 12v. --- End quote --- Did you check with a scope or a DMM in AC? |
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