Apollo 13, April 13 1970

55:55:20 (9:07 PM CT) - Swigert: "Okay, Houston, we've had a problem here."

55:55:28 - CapCom: "This is Houston. Say again please."

55:55:35 - Lovell: "Ah, Houston, we've had a problem. (pause) We've had a main B bus undervolt."

55:55:42 - CapCom (Jack Lousma): "Roger. Main B undervolt. Okay stand by 13, we're looking at it."
55:56:10 - Haise: "Okay. Right now, Houston, the voltage is a... is looking good. And we had a pretty large bang associated with the caution and warning there. And as I recall, main B was the one that had an amp spike on it once before."
55:56:30 - CapCom: "Roger, Fred."
55:56:54 - Haise: "In the interim here, we're starting to go ahead and button up the tunnel again."
55:56:57 - CapCom: "Roger."
55:57:04 - Haise: "That jolt must have rocked the sensor on, see now on O2 quantity 2. It was oscillating down around 20 to 60 percent. Now it's full-scale high again."
55:57:22 - CapCom: "Roger."
55:57:30 - Lovell: "And Houston, we had a restart on our computer. We had a PNGS ("pings") light and restart, reset."
55:57:37 - CapCom: "Roger, restart and a PNGS light... (correcting himself) restart on the PNGS, and reset on the computer."
55:57:44 - Lovell: "Okay. And we're looking at our service module RCS helium 1. We have, B is barber poled and D is barber poled, helium 2, D is barber pole, and secondary propellants, I have A and C barber pole."
55:58:07 - Haise: "Okay, AC 2 is showing zip. I'm going to try and reconfigure on that, Jack."
55:58:13 - CapCom: "Roger."
55:58:25 - Haise: "Yes, we got a main bus A undervolt now too showing."
55:58:29 - CapCom: "Main A undervolt."
55:58:29 - Haise: "It's reading about 25 and a half. Main B is reading zip right now."
55:59:38 - CapCom: "Standby one, Jim. (pause) 13, Houston. We'd like you to attempt to reconnect fuel cell 1 to Main A and fuel cell 3 to Main B. Verify that quad delta is open."
56:00:53 - Haise: "Okay, Houston, I'm showing that, I tried to reset and fuel cell 1 and 3 are both showing gray flags, but they're both showing zip on the flows."
56:08:47 - CapCom: "13, Houston. We'd like you to open circuit fuel cell 1. Leave 2 and 3 as is."

Haise: "Okay. I’ll get to work on that."

56:09:07 - Lovell: "That's AC? Okay. Yea, that appears to be what we're seeing. Okay. (pause) And it looks to me, looking out the hatch that we are venting something."

56:09:10 - CapCom: (over Lovell) "Roger."

Lovell: "We are, we are venting something out into the, into space."

CapCom: "Roger. We copy you're venting."

Lovell: "It's a gas of some sort."

Houston, we've had a problem