30/50.... you've got a valve knocked out or you've broken high side line,
inside the "can" and probably happened during the "recharge".
I'm sure someone on here, can help you out, if you want it done "right"...
Eric - He seemed to do everything as I've read described here - he used a leak detector and found a leak on the low suction side near the evap. He fixed that, added ports high and low side, and vacuumed to 500 micron. It held the vacuum.
He installed a new dryer and refilled with 1lb of R12.
When he came back to look at it, he ran the leak test again (with the specialized tool) and detected nothing.
You say the high line could be broken - INSIDE the can??