Detective work on an faulty JVC projector - Page 1
Forum section: electronics / beginners

author: topbanan
author_rank: Newbie
timestamp: November 06, 2017, 01:41:00 pm
content: HiI'm a software engineer by trade, so pretty familiar with serial interfacing and so on, but I haven't picked up a soldering iron for years.I'm trying to fix a 'spares or repair' home cinema projector, partially because the repair cost will likely be astronomical, and partially just for fun.I'm pretty sure the previous owner has blown the HDMI receiver chip, and perhaps some surrounding circuitry, because he was plugging in a new source when the unit went down. It's a 144 pin chip with a central grounding ePad (yuck), so swapping it out isn't trivial or without risk! So I thought I'd use a logic analyser to see which bits of the board are still working. The main processor and the HDMI receiver talk to each other via I2C, and this seems pretty easy to analyse, but it does bring me to my question.Since I2C is directional using the same lines for RX and TX, is there any way to tell whether the master or slave is talking? Also, I've found datasheets for the HDMI receiver, but no detailed design docs for the I2C protocol. Is there a relatively easy way to get your hands on this info, or does it require NDA's and all that jazz?Advice on my overall approach would also be appreciated, as I said, I'm new to the electronics side of things!Cheers

author: ebclr
author_rank: Super Contributor
timestamp: November 06, 2017, 02:19:42 pm
content: Wil be easier to take a picture of the IC too help people here identify the IC, then find out if the datasheet has the protocol there, But you can also use sigrok with a cheap logic analyzerThis may helpshttps://media.blackhat.com/bh-eu-12/Davis/bh-eu-12-Davis-HDMI-WP.pdf

author: topbanan
author_rank: Newbie
timestamp: November 06, 2017, 03:09:18 pm
content: Hi, thanks very much for your reply. I'll have a look at sigrock - looks very interesting!The chip is a SiI9233.

author: abraxa
author_rank: Frequent Contributor
timestamp: November 06, 2017, 06:15:30 pm
content: I'd start with the basics before homing in on the suspect:Does the unit power up normally?If not, what does happen and what doesn't happen?If nothing happens, are the fuses okay and are there any obvious signs of damage to anything inside the projector?etc...The reason being that *if* the chip is the culprit and causes a short on one of the power supply rails, it'll have to go one way or another. If it's *not* the culprit then you can test the projector with one of the other inputs.

author: topbanan
author_rank: Newbie
timestamp: November 06, 2017, 09:35:57 pm
content: Hi Abraxa, thanks for showing an interest!Yes it begins to power up, but blinks a fault code (5 red flashes) and the bulb doesn't illuminate. It's something other than a bulb issue, because everything up to 4 red flashes is in the user manual, and bulb / ballast issues are reported. Unfortunately the service manuals aren't available to mere mortals.No obvious sign of damage or burnt out components on any of the boards. I will probe the power levels at the IC's, but I'm currently waiting for the postie to send me some SMD clips!Cheers

author: abraxa
author_rank: Frequent Contributor
timestamp: November 06, 2017, 10:22:22 pm
content: Did you see this by chancehttp://forum.blu-ray.com/showthread.php?t=249815?Also, please be careful when probing around because the bulb/ballast section has nasty caps and voltages.

author: topbanan
author_rank: Newbie
timestamp: November 07, 2017, 03:31:50 pm
content: Interesting. That's the same board that the HDMI receiver lives on. I certainly wont be sending it to JVC at that price!There's not much I can do at the moment until my test kit arrives