Help identifying a chip - Page 1
Forum section: electronics / general

author: rexxar
author_rank: Frequent Contributor
timestamp: January 21, 2014, 01:34:25 am
content: Yes! It'sanotherchip ID thread! I can usually findsomethingabout a given chip, but I'm totally stumped here.This chip is in the instrument panel of my car, and it drives the tachometer. Either it or the micro has failed, because the needle is stuck at 4000RPM, and moves backwards when the engine revs up. It's not mechanical, because the needle falls back when the power's off, so something is actively moving it to 4000.I don't know what kind of device it is that moves these needles, it's a 4-terminal thing, and it looks like there's 4 groups of windings. The chip that drives it is a DIP-16 from Cherry Semiconductor, and the part number is 4632980. Looks like it was made in the middle of 1998, which was about when my car was made. I can't find anything on this device. It's got three lines running to a Harris part 4651254, which I'm also having trouble identifying. It may be a shift register or IO expander of some description, as all of the gauge ICs feed into it. (Most of the micro's IO is taken up driving the VFD)There is an identical chip driving the speedometer, but I don't want to swap them and risk damaging the speedometer, which works fine. The car is a 1998 Dodge Stratus, if that helps at all.Who would have thought it'd be this hard to find a datasheet of a 16 year old chip from a company that got absorbed in 2000? Any help would be greatly appreciated. I'll keep looking in the meantime.

author: Rerouter
author_rank: Super Contributor
timestamp: January 21, 2014, 02:20:29 am
content: Its a cross coil gauge (sine/cos meter movement)take and image of the pcb and i can say whether i have seen it before of not (automotive instrumentation technician)With these kind of gauges, the part numbers are private, with no public datasheet, so you may face better luck walking down to your local wreckers and digging out a cluster for ~$50, here in aus there is a supplier of some replacement boards, but they do not deal with the public

author: rexxar
author_rank: Frequent Contributor
timestamp: January 21, 2014, 02:46:42 am
content: I'm thinking these are all proprietary chips, most of the chips on this board start with 465 or 463. I guess the only option is to go pull one from a junkerEDIT: I should mention that I've gone through and reworked all of the solder joints on the ICs and connectors, as they seem to be a common failure point on these instrument clusters. I had this problem before the rework, I was hoping that would fix it.

author: rexxar
author_rank: Frequent Contributor
timestamp: January 21, 2014, 05:35:03 am
content: This instrument cluster has a self-test that moves all the gauges around, so I've been feeding it 12V and using that to test. It looks like the micro sends a PWM signal to the driver chips, which move the needle based on the duty cycle. It looks like the tach and speedometer drivers are getting the same signal (with slightly different values), so I'm relatively confident that the micro is good, and this one driver chip has failed.I suppose it doesn't matter much, since it seems unlikely that I'll find a replacement chip. Ah well, there were a few other bits that I wanted to find replacements for at the junk yard anyway.I did look for cross coil driver chips, just to see if I could find something that even looked similar. All I found were patents.I'm bad at google.EDIT: Actually, I think I found it! 'cross coil driver' returned results for 'air coil', so I searched for that, and I found the CS3750, which has the same pinout as my mystery device. I'm gonna try to track one of these down, and see what happens.Thanks very much Rerouter for ID'ing the gauges!