K1c key 111 unknown exception repair “successful”
Recently picked up a k1c with the key 111 error, seller said that they had a hot end blowout and then got the error after replacing everything and gave up.
Upon examination this version of the k1c uses a serial comm converter chip to convert ttl signals 1.5v to rs232 signal. 5v. Both the chips in the hot end and in the motherboard were present but not outputting 5v signal. Quick trip to digikey.com and I got replacements. Chips (marked u28 in the picture) are 3PEAK 3232E-S03RCT-ND. I bout 10 of them at 6.62 total so .662 cents each.
I was able to swap both chips on the boards and restore comms and get the printer running again. Total parts cost with shipping was like 10-12 dollars. “I ordered other stuff with them” anyways best way to see if it is that chip is alive is to test voltage on the green and white wires at the head. 5v bouncing on both chips are transmitting data. Mine were outputting .5v causing no comms between the hot end and the motherboard. Restoring the hot end restored 5v to white while restoring the chip on the motherboard restored 5v to green. Each being transmit and receive on the head respectively.
Capacitors around the chips measure normally .2mfd on c286 and c287 on the last cap c288 is .1mfd these will also kill your signal.
Both the hot end and the motherboard have identical chips and cap setups so the pic is good for both.
I am posting this here to try to assist with saving others from replacing the hot end pcb and the motherboard over some cheap replacement chips. Hope this helps someone