The Espresso Machine Restoration site
A non-commercial site for those interested in espresso equipment repair and restoration.
|GB/5 & FB80 steam valve
|I had an email from someone saying that the GB/5 & FB/80 steam valves are real pigs to change and rebuild. I
haven't had any problem with the valves in my customers machines so was intrigued to find out what the problem
with them was.
In short - there isn't any problem at all.
Let's say that you have a drip from the steam valve and it needs work. There are 2 possible causes.
1. Somehow the adjustment set screw (aka grub screw) is causing the valve to open when it should be closed.
2. The internal seat gasket is worn and needs replacement.
Understanding the valve operation
The valve works the opposite way to the Linea steam valves, in fact the GB/5 valve is very similiar to Faema E61
Linea & FB70 - the valves use a strong spring that pushes a seat gasket AGAINST the steam pressure. Most leaks
from this valve are attributed to the spring weakening then the seat gasket going hard. To release steam you turn
the knob anti-clockwise which PULLS the steam shaft towards the barista.
GB/5 & FB80 - these valve use a spring pushes WITH the steam pressure. Although I haven't had any leaks as yet
I would attribute it to a bad seat gasket or incorrect adjustment of the set screw (grub screw) which is in the knob
assembly. To release steam you again turn the knob anti-clockwise but it is reverse threaded and therefor PUSHES
the steam shaft away from the barista.
POWER OFF AND STEAM PRESSURE AT ZERO!
Taking the knob off
First job is to carefully undo the white insert by turning it anti-clockwise. When that has been removed you will see
two nuts. Grip the knob with one hand and with the other use an 9mm socket to remove the top nut first then the
other nut. If you try both together you will be there all day.
With both nuts removed you will then see the black steel set screw. By taking a few moments to turn the knob in and
out you will get an idea of how the valve works. By opening the valve the knob goes away from you (reverse
threaded) and it causes the black set screw to push against the main steam valve shaft, thereby pushing the seat
gasket away and letting steam escape.
If you have a drip on a new machine or a fairly new machine I would first check to see if the set screw isn't pushing
against the steam valve shaft in the off position. It's a bit like a clutch on a car, you just need to feel when the pin
and screw are touching (clutch biting).
Don't attempt to remove the black knob now - you can't.
Removing side panels
Yes I'm afraid the side panels need to come off - for those of you with FB80 this will be a very painful experience
that involves a lot of work. Serves you right for being so flash!
For us sensible people with GB/5 you will only need to take off the side you are working on.
Remove the cup tray and the cup tray pan. Loosen (not remove) the black corner trim pieces. For this use a 4mm
allen key (hex key). You only need to loosen them so the side panel can slide out. Then undo the 2 phillips head
screws. Again loosen not remove. The side panel will then come off - but be careful because the corner
piece with the lion is loose and needs to come off first.
Removing the valve itself
A 17mm spanner is required to loosen the copper pipe end nut. However (not shown in the picture) you will need
another spanner to hold the end part of the steam valve (the bit the 17mm nut screws onto). If you just use a 17mm
spanner and undo it the back part of the valve will probably undo as well.
By now you have probably been tugging away at the black knob on the front wondering how on earth it comes off.
You need to undo the bolt from the rear. The bolt prevents the steam valve turning more than 180 degrees. Get
you 8mm socket out and undo it completely.
Now you can undo the black knob by turning it clockwise.
Lastly use a 24mm spanner to carefully undo the front retaining nut. I always use masking tape to prevent any
scratches to the fascia panel. A bit of manipulation and the valve will come out in 1 piece.
The valve is now very easy to take apart and replace anything that needs doing. Most probably just the seat gasket
but also maybe the spring. You can see how the valve works now.
Putting it all back together is just the opposite.
However there is one small part that is quite tricky. That is when putting the black knob back on and then inserting
the 8mm bolt through (the one that means the knob only turns 180 degrees). This will be trial an error if you want it
back the way it was. The most important part of this is how the black steel set screw opens the valve and shuts it at
the right time.
|This website is created by Paul Pratt, Hong Kong 2004-2007. If you would like to use any of the images or text I am
sure I will say yes, but please ask first!
Email me here.