Help me identify a chip - Page 1
Forum section: electronics / repair

author: tonyh88
author_rank: Regular Contributor
timestamp: November 14, 2023, 05:38:24 am
content: Hello I'm trying to repair a carrier furnace control board.The output relay for the fan inducer motor is not getting activated. The relay itself is working fine but the power for the relay coil is inexistant. Tracing the circuit the signal is coming from the mysterious chip circled in red in the picture. UN2003A chip is also part of the relay driving circuit but this was also tested and it is good.Motorola logo on the mysterious IC but I can't find anything on google looking for the numbers on it. It would need to be some kind of microcontrollerLet me know if anyone knows what this IC is.Thanks!

author: ataradov
author_rank: Super Contributor
timestamp: November 14, 2023, 06:13:14 am
content: This is a custom marked MCU, likely PIC. Even if you find the exact MCU, it would be useless without the firmware.I'm guessing this based on the fact that a whole bunch of numbers on the board start with "CE" and have the same general format.

author: DavidKo
author_rank: Frequent Contributor
timestamp: November 14, 2023, 08:24:40 am
content: Or it can be already custom "preprogrammed" chip from Motorola to save the money.

author: Haenk
author_rank: Super Contributor
timestamp: November 14, 2023, 11:05:33 am
content: That logo is "Microchip" and not Motorola.

author: tonyh88
author_rank: Regular Contributor
timestamp: November 14, 2023, 12:47:03 pm
content: too late at night, yup microchip logo don't know why I said motorolaThanks for the informations everyone.Makes sense to be some kind of custom micro as all the furnace sensors are connecting back to it through some signal conditionning. Something in here needs to control the sequence of operation for furnace ignition and there is not much aside from a lot of passives components.That being said that's not great for my chance at repairing this thing. I'll doube check for cold joints and verify all passives again tonight. Otherwise I see some of those board that were removed from functioning furnace on ebay are realtively cheap. I guess I'll have to take a chance and buy one.Thanks again

author: Haenk
author_rank: Super Contributor
timestamp: November 14, 2023, 01:23:05 pm
content: You could still check for life on the board with a scope - and selenoids like to fail as well, maybe check those. However if replacement boards are cheap, that would be my way to go

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 14, 2023, 02:44:41 pm
content: Seems like a pic16f876a, maybe a mask rom version.

author: amyk
author_rank: Super Contributor
timestamp: November 14, 2023, 02:46:31 pm
content: Likely to be a PIC16 series.

author: wraper
author_rank: Unknown
timestamp: November 14, 2023, 03:26:52 pm
content: It could be mask ROM version of PIC16C57 or something similar.

author: KG7AMV
author_rank: Frequent Contributor
timestamp: November 17, 2023, 01:06:54 pm
content: If the chip is toast this following method will not work, but if you have a known good chip. What I have done in a situations with a custom marked MCU is use one of My Xeltek Programmers (Superpro 6100N or 7000) Search DIP28 under mfg Microchip and Go down the Line of chips attempting to read it. Generally the software will yell at ya if the device signature does not match. It is time consuming but You may get lucky but most likely it is read protected so if you do get a device signature match it cannot be read.This is why we need right to repair laws a $3.00 micro-controller should not condemn a board which prob cost s a fair amount to the recycle bin.