Eric, I'll do some volume measurements as well. As far as the opening size on the restrictor, I believe it's smaller than a mm. In fact, if you have a dime around, look at the picture I posted at the beginning of this thread - you can see the hole is roughly the diameter of lower part of the "8" in 1988. To be more precise, I'll mic it.

Pat, any tips on the swap-out of your pump? Did you get the replacement from Stefano? I just called them about this and told them I don't need the OPV - after which they told me I need the version of the pump that uses a power plug that includes a diode. Need to dive into this a bit more to figure the purpose of the diode, but I'm guessing it's some kind of overload protection.

If you have a friendly hardware store, check the size with their numbered drills. As regards the plug with the diode, I have all of that including the pump in case you run into trouble. Email me offline: erics at erols dot com .

BUT, your machine should already be equipped with that plug and the (maybe?) diode - see this for more info:
http://www.fluidotech.com/Pages/en_mono ... eries.aspx

Good idea - I'll ID it with a drill bit.

As for the diode - I currently have one that should be okay (thanks very much for your offer!).

My current pump:

Well, you may/may not have one BUT that's OK. That plug just lifts off after you remove the screw. The temperature diode is sorta hidden.

Normally an original fluid-o-tech connector has the diode build in (solder) inside
in some other case the diode will be on the motherboard
and in some other it will need to be connected externally like Eric says

Thanks Stefano. I spoke to Kathleen earlier today in my search for a replacement pump. Once I confirm some additional details (diode, exact thread-type and -size, etc.) I'll be placing an order with you.

Dear Ras

I've bought the pump in Switzerland by a specialised service centre (http://www.olympia-kaffeemachinen.ch/home.htm).

On the pump I've dismantled (blue ceme pump) it was connected directly with a connector from the neutral and positive phase. I've reinserted it in the same way without any thought that there should be a diode...

I will post a picture this evening how it is installed now and working fine for almost 5 weeks.

Best regards
streezz

The diode which Fluid-o-Tech (F-O-T) refers to in the link I provided is a thermal diode which shuts off power to the pump when it senses an unusually high temperature in the coil windings, i.e. running the pump for several minutes with no cooling off period. Most (but not all) espresso machine pumps are so equipped. The Ulka (now CEME) have a little "pocket" for this thermal diode and it is readily visible. Do you need it for the pump to operate? - No. Is it a nice safety feature - Yes.

The other type of diode (definitely not readily visible) blocks 1/2 of the AC voltage cycle supplied to the pump and is inherent to the operation of the pump's "motor".

Please find my pictures below.

This setup runs smooth without any issues.

best regards
streezz

Pat, sure looks like mine! One difference is that I've insulated my boiler (with 300-degree F foam), which keeps the water reservoir nice and cool, and seems to reduce the amount of time, and frequency for which, the boiler is on.

OK, I think I've gotten to the bottom of what's going wrong with my pump. I took it apart last night and noticed that I'd pinched a gasket to a point where I need to replace it. But the pump-pressure/low-flow issue seems to be caused by a tear in another piece (I'd call it a baffle, or seal, but I'm sure there's a more correct term) that is part of the actual piston assembly. Some pictures:
Gasket I wrecked in a incorrectly-done pump reassembly:


Picture of the piston-assembly; the rubber seal/baffle at the top has a tear in an inner ring/indent


Tweezers pointing to the piece with the tear... Now if I can just get a replacement, I'll be back up and running with the original pump