Embedded Computer using MC68340 - How would you tackle this problem ? - Page 1
Forum section: electronics / projects

author: Fraser
author_rank: Super Contributor
timestamp: December 16, 2012, 11:04:32 pm
content: x

author: PhynixViking
author_rank: Regular Contributor
timestamp: December 16, 2012, 11:39:29 pm
content: Hmmm... a bit complex of a board there. Did you happen to check those 4C4001JDJ RAM chips? Just a hunch... I'm so use to RAM chips going out like light bulbs. Good luck! If I end up thinking of anything I'll have to post it.

author: JoannaK
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:32:00 am
content: It's been years since I have last touched 68k Embedded.. So I'm a bit rusty.. But..http://cache.freescale.com/files/32bit/doc/ref_manual/MC68340UM.pdfbrings back memories.What I'd would start is to check datasheets of the most obvous chips and backtrace/sort (with Ohm meter continuity beep) out the voltages needed for the board and to check power supply (Voltages + ripple/noise) in case the Electrolytes/tantals have gone bad. Obviously there is a lot of +5V parts but most likely there will be some other voltages for analog stuff.For debugging, it was quite common trick at the time to add some extra I/O just to get 'visible' indicators out of the system. We used to have either Serial port and/or typical 2*16 char epson-controller LCD for system debug purposes. Those help a lot, when you are testing the system. So I'd check if there's any obvious connector/header that might have 68340 UART pins. Also finding Max232 (or derivate) on board would be lucky indeed :-)Mc340 seems to have JTAG and BGD in it, so if you can find tools for those, they might give indication if the CPU itself is running. Of course simple checking Addr/data lines could tell that much. Those programmable logics may also have Jtag, but I doubt they woudl have been left unprotected.

author: PhynixViking
author_rank: Regular Contributor
timestamp: December 17, 2012, 02:59:56 am
content: ...If you did desolder... idk if this is a crazy idea but I'd almost say try to desolder at lower heat using a copper braid... I know that might sound crazy but I think it might be safer for parts around those chips and back of the board (other side parts) as long as you have a fairly steady hand.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 05:27:40 am
content: Check power supply first, you should find 5V, 3V3 and a pair of 12V rails, along with a -12v rail or so for the LCD. More likely the psu than the mainboard, though easy to check the databus is running on a scope so you can see it is running a program and is not stuck.

author: amyk
author_rank: Super Contributor
timestamp: December 17, 2012, 09:38:37 am
content: Since you're more familiar with analogue, how about seeing if you get a video signal from the camera itself?This might be worth watching too:

author: nctnico
author_rank: Super Contributor
timestamp: December 17, 2012, 11:04:02 am
content: I'd start by checking the voltages with a scope. They should not have large ripples on them. I see a lot of tantalum caps these are prone to shorting so worth checking. The problem could be as simple as a bad soldering joint. Before doing anything you should check the solder joints using a magnifier and a needle. If it is not a soldering problem you need to use a scope to look at oscillators, address and data lines to see what is alive and what is not.