Volvo 850 ECC Testing/faulty?

Navy · Post by **Navy** » 10 Mar 2020, 12:27

Hello and many thanks to everyone for replying.
jreed. I tried several times to do a diode test but I get no reading either way. I tried to clean the diode and the left side just lifted away from the metal tang without any pressure infact It probably burnt through and separated before I started testing/cleaning, I suspect this may be my issue.
The quality of my photos are not the greatest as the pcb is still in perfect condition around the diode (the first pic is probably the best) also I am 100% sure the capacitors have no leaks even though the pics show some sort of residue. The two forward resistors (4701 - 1501) measure within range on my dmm.
The burnt diode has the very slightest impression of the letter and number A2 on the right side which matches diode D5 perfectly.
I have no idea where to source one of these A2 diodes. Do they vary in voltages/current switching speeds? I have no idea.

Abscate, that is such a generous offer!!! I am almost certain my ECC is working as the voltages at the pins all match the service manual.
However I may still be in the market for a power stage if this diode issue doesn't bear fruit.
BTW there isn't a beach anywhere like Maracas.

Scot850, sadly my phone camera is not really up to the job.....I am sure the capacitors are not leaking but I will most certainly change them if I can get the power stage to work as I understand 26 years for a capacitor is borrowed time and then some.

Thank you so much for taking the time to help me
André

Navy · Post by **Navy** » 10 Mar 2020, 12:37

: IMG_2020-03-10_18-37-29.jpg (286.17 KiB) Viewed 989 times

Post by **jreed** » 12 Mar 2020, 18:13

It looks like D4 overheated and failed. I wonder if there is a schematic diagram available for this unit? That would be a great help in troubleshooting. Until you figure out what caused the failure and fix it, it's risky to put in a known good ECC unit because it might fail too.

Post by **RickHaleParker** » 12 Mar 2020, 18:43

Heads up: There are 10 versions of the 850 ECC and they are not all interchangeable.

Navy · Post by **Navy** » 13 Mar 2020, 05:19

Thanks for replying.
So far 3 electronic component manufacturers require more information regarding the specifications of the diode. I have e mailed ALPS requesting such information and the wiring diagram too but I am not too hopeful.

I have seen condensation damage on pcb's before and I recall a faint white haze around the two resistors and diode. I am convinced the diode pin's were covered in corrosion which accounted for the failure. You may also notice some of the tell tale blue/green corrosion on the side of resistor 28 and 29.

I don't want to guess the diode's specifications but I see no other easy option. Hopefully, Alps will have the info for me.

Thanks again
André

Post by **RickHaleParker** » 13 Mar 2020, 13:20

Navy wrote: 13 Mar 2020, 05:19 I don't want to guess the diode's specifications but I see no other easy option. Hopefully, Alps will have the info for me.

Any clue who the vendor is? SMD markings.

Navy · Post by **Navy** » 13 Mar 2020, 14:10

Thanks for replying.
The only markings on the pcb are ALPS Issue M03 ANJ970IIE.
The diode has A2 printed on the surface.
I understand from component manufactures that this is not enough info. I need specs for the original diode Volts/current in and out.
Many thanks
André

Post by **RickHaleParker** » 13 Mar 2020, 14:29

Navy wrote: 13 Mar 2020, 14:10 The diode has A2 printed on the surface.

There are only two diodes on the A2 list in the link, in a Small Outline Diode (SOD ( Two leads )) package .
Vishay Diode 1N4148WS and ROHM Zener diode UDZS5.1B.

If where to bet, I would bet on the 1N4148 because you have more then one on the board and Zener diodes are not so common.

Post by **jreed** » 13 Mar 2020, 17:59

If it's of use, I could open up my spare ECC unit and inspect/measure the diode in it. It might not be the same version of the ECC unit that you have in your car, though.

Post by **jreed** » 14 Mar 2020, 10:14

I took apart the ECC unit I got out of a 1996. It doesn't look like the pictures of yours. I did notice that the silkscreen labels show "ZD" for zener diode and "D" for diode. That may mean that your failed component is more likely to be a diode instead of a zener diode. You could check your board to see if there are any components labeled with the "ZD" prefix.
This ECC is labeled 9166550 W605K on the outside sticker.
The circuit boards are labeled ALPS ANJ 97813F (small upper board) and ALPS ANJ97812J ISSUE M11 (larger lower board)