While I don't have a jockey box, I'm borrowed another one again. And I'm having trouble to get a good pour. There are bubbles in the system that never ends, it never happened before to me. Always after some glasses the system became stable, but this moment never comes with this setup, and the beer is 'choking' when leaving the faucet, till the end of the keg. Any clue? The keg and gas tank/line are the same, and my carbonation process too.
The system sounds to be unbalanced. If the inner diameter of the chilling coil in the jockey box is different than the one you've used before then the resistance is certainly off creating the unbalanced performance. A lot of foam and sputtering output at the faucet is normally caused by too low a serving pressure.
I'd say up the pressure and see what you get. You may want to open the faucet and slowly dial up the pressure to see it improve with while pouring. Then stop when its right. You may think this is a waste of beer, but you are wasting beer as foam anyway so it can't hurt that much.
I've changed the faucet, the coil, the serving pressure, put more gas, purge some gas, removed the gas line, and nothing makes difference on the 'choking' thing, just on foam ammount and beer flow.
So I remembered one tip that I've read on other question here in StackExchange sometime (and was not able to find it again to share now). It was a question on drink from a keg without gas tank.
So, I've changed the liquid-out quick disconnect to my gas-in, and lay my keg above the jockey box. Both on the table, but the keg layed on a chair, with the beer line plugged in the gas-in hole. And with no CO2 attached, just let the beer flow by gravity.
At this moment I've understanded that my problem was in the keg. In the liquid side, to be more accurate. Don't know yet if it was the post sealing, or the poppet, or the dip tube that maybe was clogged, but the thing that was 'choking' my beer was in the 'liquid side' of the keg.
Its very good to know that this technic works so well. After that we just drinked the beer with very good pour. When the beer is ending, you can just upside down the keg or make your possible to put the gas hole where the beer want to be by gravity force and wait it flows by your iced coil.
EDIT: All rigth, people, after 2 more utilizations of my system with the same keg and a just fine pouring, I can attest that the problem was the liquid diptube. I changed it with other keg sigthly different. When disassembling for cleaning I've mixed them. The other keg remained with beer on the bottom, and these was with the tube so pressed to the bottom. So the 'choking thing' was just the beer having a bad time to pass through. Thanks.