I've recently noticed the brew pressure drops by about 1 Bar when the heating element kicks in. You can hear that "click" sound when the heating element kicks in, and see a bit of a spark inside the electrical box mounted on the back wall of the case, next to the OPV.
Is it possibly a power supply problem that has caused the pump to fail? Is it possible that the new pump I install may fail within weeks because of a power supply problem somewhere further back?
I found the pump on eBay for $35 plus $7 postage to Australia.

A drop in brew pressure when the element is powered is normal. The "about 1 bar" is a little more than what I would expect (normally around 0.50 bar) but that may be due to your kitchen wiring situation.

Your OPV situation is NOT designed for a 9.0 bar extraction and that is WHY Bezzera came up with a kit as I previously stated. The o-ring you previously referred to is designed to seal when the "adjuster" is screwed all the way in. The 9.0 bar kit fixes that . . . so . . . why not order that kit instead of a pump you may not really need?

And now, since you have honed those necessary skills re OPV disassembly , why not start over and adjust the valve to give 9.0 bar with the heat element OFF and post another video ?

I got this espresso machine from idrinkcoffee Canada, and old mate told me that all Bezzera machines imported to Canada are supposed to be set to 9 Bar by the manufacturer, but sometimes a few machines slip through with the 12 Bar setting. I told him mine was on 12 Bar and he said it was a mistake.
I might end up getting the 9 Bar kit, but that won't solve the problem. From the beginning it was either the pump or the OPV. I've taken apart the OPV and cleaned it, and it still fluctuates... so it must be the pump.
I don't have enough knowledge of electronics to know why the pump is playing up, probably a burnt out diode or whatever, but I do know the OPV is sparkling clean. It's just a spring and a hole, so there's not much that can go wrong with it besides it getting stuck.
Yeah, it's probably more like a .5 Bar drop, I probably just wasn't paying enough attention to the gauge.
I'll post a new video with the new pump in about two weeks. It will be a video of me making a great coffee I hope.

I replaced the pump today and the machine works fine now. I took the old pump apart and the plastic ball check valve was not deformed. There were no signs of mechanical failure within the pump, which leads me to believe the coil may have overheated or the diode, which is basically part of the coil, burnt out due to excessive use. I followed the instructions from idrinkcoffeecanada youtube video on how to descale a heat exchanger machine, and he said not to run the pump for more than 1 minute with 2 minute breaks in between. The level sensor was disconnected in order to overfill the boiler purposely, to descale the entire boiler and the level sensor. Well I saved hundreds of dollars by doing the repair myself and went through the correct troubleshooting steps. It was good to clean the OPV because it had a bit of gunk caked on it anyway, and it's pretty easy to take apart. I enjoyed working on my machine. Thanks to the guys with experience here who gave me a lot of useful info.

sorry for joining the thread after the problem seems solved, but I did not understand well what was the real cause and at what pump pressure (as indicated by the gauge) are you running with blind filter;
what I would notice:

- I have a Magica (E61), quite diff from BZ10, but with the same pump and (, initially,) 12 bar OPV (at least according to parts catalog); Bezzera policy is for a standard 12 bar pump pressure, that is, say 11-11.5 bar above the puck;
With a setting of 12 bar OPV, I cannot imagine how is possible to manage a 9 bar shot in normal accepted parameters (2-2.5 ml/sec flow, for a 25 sec, 50-60 ml double), without having fluctuations on the gauge! the hidraulic resistance of the puck is not constant during extraction, therefore the flow varies accordingly; not considering the - confusing for me - problem of the excess flow: an ULKA EX5 have at 9 bar, about 260 ml/min, that is double the required flow for a normal extraction; where goes the excess flow? normally, in such a case, with a proper resistance from the puck, would increase the pressure and drop the flow; in fact, at 12 bar, the flow is just about the required one for a normal extraction;

- on the other hand, in their poor Magica/Mitica user manual, chapt 7 - Troubleshooting, they diagnose "pump's pressure is too high (>10 bar)" or "too low (<9 bar)", along with providing a 9 bar kit - which I have installed almost a year ago; the (old?) 12 bar OPV was in a marginal condition at 9 bar and several people, including me, experienced that "squealing" sound, in fact a resonance vibration of the spring, as I think; perhaps now, they have changed the spring, as that 9 bar kit is no more included in the accessories catalog;

- so, for the vibrating pump versions of Bezzera's I would say that the best extractions are at the OPV set pressure, that is, the pressure is no more an adjustable parameter during extraction; and is better this pressure to be the 9 bar; this is not a pressure profiling machine...

in fact, a regulated pressure such is by the OPV (or a 9 bar rotary pump with bypass), is better for the quality of the shot, as pressure fluctuations mean flow fluctuations, and in turn, temperature fluctuations; in my Magica, at 9.5 constant pump pressure (gauge), the temp profile of the extraction for a normally prepared puck (double, as with singles, the flow is even slower...) is quite liniar after the initial HX hump of, say 10-12 secs;

sorry for joining the thread after the problem seems solved, but I did not understand well what was the real cause and at what pump pressure (as indicated by the gauge) are you running with blind filter;
what I would notice:

- I have a Magica (E61), quite diff from BZ10, but with the same pump and (, initially,) 12 bar OPV (at least according to parts catalog); Bezzera policy is for a standard 12 bar pump pressure, that is, say 11-11.5 bar above the puck;

radudanutco wrote:With a setting of 12 bar OPV, I cannot imagine how is possible to manage a 9 bar shot in normal accepted parameters (2-2.5 ml/sec flow, for a 25 sec, 50-60 ml double), without having fluctuations on the gauge!

the hidraulic resistance of the puck is not constant during extraction, therefore the flow varies accordingly; not considering the - confusing for me - problem of the excess flow: an ULKA EX5 have at 9 bar, about 260 ml/min, that is double the required flow for a normal extraction; where goes the excess flow? normally, in such a case, with a proper resistance from the puck, would increase the pressure and drop the flow; in fact, at 12 bar, the flow is just about the required one for a normal extraction;

- on the other hand, in their poor Magica/Mitica user manual, chapt 7 - Troubleshooting, they diagnose "pump's pressure is too high (>10 bar)" or "too low (<9 bar)", along with providing a 9 bar kit - which I have installed almost a year ago; the (old?) 12 bar OPV was in a marginal condition at 9 bar and several people, including me, experienced that "squealing" sound, in fact a resonance vibration of the spring, as I think; perhaps now, they have changed the spring, as that 9 bar kit is no more included in the accessories catalog;

- so, for the vibrating pump versions of Bezzera's I would say that the best extractions are at the OPV set pressure, that is, the pressure is no more an adjustable parameter during extraction; and is better this pressure to be the 9 bar; this is not a pressure profiling machine...

in fact, a regulated pressure such is by the OPV (or a 9 bar rotary pump with bypass), is better for the quality of the shot, as pressure fluctuations mean flow fluctuations, and in turn, temperature fluctuations; in my Magica, at 9.5 constant pump pressure (gauge), the temp profile of the extraction for a normally prepared puck (double, as with singles, the flow is even slower...) is quite liniar after the initial HX hump of, say 10-12 secs;

I set the OPV to roughly 12 Bar to troubleshoot the problem with a blind basket. I have it set at 9 Bar when making coffee, but this was just a troubleshooting step. You should watch both Youtube videos and read the entire thread to understand, but I'll sum it up here again:

* One day when making a coffee, the gauge started to fluctuate. This is with the OPV set at 9 Bar as usual

* I put in a blind basket and it went up to 9 Bar ok.

* Then I set the OPV to 12 Bar, which showed the pumps weak performance, ie, it took a very long time to get up to 12 Bar. It was actually set above 12 Bar, but I'll never really know what it was set at exactly, because I couldn't keep the pump running for more than 1 minute.

* I took the OPV apart and cleaned it because the other guys told me to... didn't solve the problem

* Then I replaced the pump... and that solved the problem.. The old pump was dead basically.. that's the answer.