Cassese guru required

[John]

Our trusty Cassese 276 has taken to delaying the wedge insertion by 6 to 10 seconds.

The delay is accompanied by constant hissing from the unit highlighted in the photo, and the hissing ceases after the wedge has been fired.

Apart from this behaviour the machine appears to be functioning correctly in every other way.

Pressure has been set at the recommended 6 bar.

Can anyone help?

[Nigel Nobody]

John,
I'm certainly no guru and I imagine you've already groped around in there to locate the air leak. Maybe one of the hoses has come a little loose or has a split in it. Any disruption to air flow through the machinery might cause the delay!

It could also be a valve inside that little box that's stuffed!

Isn't there a Cassese technician somewhere in UK?

[LeFrisp]

Did a bit with pneumatics about 20 years ago.
I would guess that on the rear of that panel, looks like an air distribution panel to me, there are air inlets and outlet ports one of which may be loose/ or leaking. Im guessing but the delay in firing will be something to do with a sensor wanting the pressure to build before firing the wedge. I would get in behind that valve and see what is in there.. If nothing is obviously loose on the back of the panel I would look at stripping the valve, Could be as simple as an o ring worn out..... If it is the valve you will want someone who knows what they are doing to look at it.

[Mark Thornton]

Hi John

The C1 differential valve fitted to your cs276 has ceramic disc's inside - so no O rings therefore it can't be worn out, don't remove it from the logic board as it will serve no purpose.
First the bad news: the C1, C3, C5 & C7 valves are all interlinked via the board and all rely on the others in the link working in order for the machine to fire the wedge the fault could be with any of the valves or sub valves as air will always find the easiest / quickest escape route it may not be the C1 valve that is faulty.
You maybe fortunate in that the air could be escaping because some airline contamination is stuck within one of the pneumatic components stopping one of the valves from seating correctly, try putting just a few drops of airline lubrication oil into the outlet pipe of the pressure regulator (mounted on the end of your machine) and then working the machine a few times which will force the lubrication through the system.
The cs276 has always been a b*tch to work on due to the over complex circuit.

Regards Mark

[John]

Many thanks for the suggestions. And a big thank you to Mark for sharing his knowledge.

Tried the lubrication trick Mark, and I think it did make an improvement, though not a cure. I even removed the C1 unit and placed a few drops in the airways.

I'm not sure if this has any significance, but we have discovered that if we clamp (foot pedal) and then delay for a couple of seconds before inserting the wedge, it works perfectly.

Further suggestions will be gratefully received.

[Mark Thornton]

I've attached a circuit diagram that may help you - a full size picture can be downloaded at: http://www.underpinner-spares.co.uk/Equ ... ircuit.jpg

As you can see the sequence for firing is:
Pedal - Firing Buttons - E3 - E4 - E5 - C3 - C5 in that order

If your firing buttons are outputting enough air then you could swap the E3, E4, E5 for the same type you have fitted elsewhere on the logic board, then swap the C3 valve for the C9 valve as they are the same type.
The C1 valve is used to reset the system once a wedge has been inserted.

Sorry for the poor diagram i've had it for many years and like me its starting to show its age.
Regards Mark

[John]

swap the E3, E4, E5 for the same type you have fitted elsewhere

Brilliant Mark!

The machine is running sweetly after swapping the Es with the As.

Thank you for your very generous help with this.

[Mark Thornton]

Hi John glad you got it working.

Just a note of warning, moving the blocks around has not cured the fault it's only moved it to another part of the circuit.
The "A" sub valves operate the reset circuit each time a wedge is inserted so you may now experience faults on this reset sequence.
Best tip would be to get yourself one of each of the sub valves and either fit them straight away or keep them for future use if a new fault occurs.

Regards Mark

[John]

I was expecting some repercussions from moving the faulty logic unit, and have been watching out for some nastiness appearing elsewhere, however so far have not noticed anything.

Foolishly I moved all three in one go instead of one at a time, so I don't know which is the faulty unit.

I will take your advice on fitting replacements, do you know where I could buy them Mark?

[Mark Thornton]

er well you could try my site: www.underpinner-spares.co.uk go to the cs276 section

[John]

The new set of logic units have been delivered and fitted.

The machine is back to normal and all is well with the world.

Thank you Mark. Great service.