In the end, I'm not sure what it was since I un-kinked the tube AND changed the OPV to 10 bar from 12-13 in one go. My guess it was the latter OPV adjustment that fixed it. Wasn't scientific enough to adjust it back to see if I could reproduce the error condition... :P
Didn't get any new parts, although I feel like having the pump/OPV assembly on hand at this point would not be too cautious... The pump was replaced a few years ago according to the previous owner, but the job wasn't done great from what I can see: new OPV doesn't quite line up due to some slightly sloppy pump mounting work, and the inlet tube didn't reach far enough into the tank so the pump would run dry when the take is only 2/3 full. This would lead to more dry pump situations which can't be good for the life... Overall, what you're experiencing doesn't sound like an electrical problem. However, at least in my case the perfectly timed pressure drops with the PID activation made me a bit suspicious... you can see this with the dot/decimal place under the temp display of the PID - when you see the dot it means the brew element is on - I've verified this with a power consumption meter after the machine is steady with the steam light off - each blink is associated with a spike in the power draw which *has* to be the PID turning on the SSR to power the brew element. This timing was bit too uncanny to ignore. It's almost like the pump is working at some electrical/mechanical limit, and when the brew element gets power switched on there's a slight drop or interference in the power supplied to the pump which results in the drop in pressure. Another theory that could support this is holding static pressure (with blind) is not quite as intensive as when there is flow (i.e. when brewing), so this is why it can hold at higher pressures but can't fully supply the 9 bars of brewing pressure when there is flow. But now this is a pretty hand wavy explanation. Anyway... this is really stretching my knowledge as an electrical/computer engineer who works with much lower power stuff and software most of the time, so take it for what its worth... :P On Sunday, 12 January 2020 14:57:36 UTC-5, Richard wrote: > > JT, > Thanks. Very useful. > > You are right, when I use a blind basket brew pressure goes to 10 and > stays there. > It oscillates only when pulling a shot. Never with the blind basket. > > I will open the machine soon and check your suggestions about the kinked > drain tube. > > I am also going to check the wires going into the PID. I had a problem > with them a few months ago and thought I had fixed it. 2 wires dropped out > of the connection. > The way the wires tighten into the PID is a little strange. There is a bar > in each slot that goes up & down when you turn the screws. The wire goes > above the bar. Turn the screws clockwise and the bar goes up and pinches > the wired against the PID contacts. > > How did you resolve your oscillation problem? Was it the pinched tube? > Did you replace the pump & OPV? > I was thinking of ordering that from WLL to make sure I have one nearby if > the pump dies. > -- You received this message because you are subscribed to the Google Groups "Brewtus" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/brewtus/304d01f4-a5d0-4672-b922-e8d980bd7f2b%40googlegroups.com.
