The Valve Plates are small plastic reed-valve like devices that are used by the pumps to control the flow of air into and out of the pump chamber. There are two pumps, and each pump has one valve plate. Here's what you do:
To begin, you'll need some alcohol, and good Phillips screwdriver with a
medium-large tip in good shape, and some swabs. If you have one on hand,
a 7/64th drill bit will also come in handy.
Remove the pump cover exposing the pumps and the vacuum hoses.
Remove the hoses from the pumps to get them out of the way.
Start with the pump facing you and remove the two flat-head screws holding
down the Pump Fixing Plate. Use care, and a good screwdriver that fits so
you don't mess up the screw heads.
Remove the Pump Fixing Plate and you can see the Valve Plate positioned on the
Pump Head. Notice how there is a notch along one edge.
Remove the Valve Plate and take a look. All that yellow stuff is residue from the solder
flux. This one is not that bad. I've seen them where it's real thick and crusty. The
problem is this stuff gets in the way of the valve flap and eventually prevents the valve
from making an air-tight seal, resulting in loss of vacuum, and little or no suction.
Take a look at the inside of the Fixing Plate. You'll find flux residue here too, both on
the surfaces and inside the air holes. As this stuff builds up, it too prevents the valve
flap from making a good seal, again resulting in loss of vacuum and little or no suction.
Start with some alcohol on a swap and clean out all of the flux residue on the inside of
the Fixing Plate. Use a fresh swap as needed and keep cleaning until all the gunk is gone.
Next, I use the drill bit to clean out the hose tube. Squeeze some alcohol from your
swab into the tube to soften up the gunk, then drag the butt end of the drill bit in
and out trying to scrape all the residue out. Clean up any that may come out of the
tube back into the Fixing Plate. If you don't have a 7/64ths drill bit, try cutting
the end off a swap and using the stick, or one of those big fat square toothpicks may
work well too, or maybe a pipe cleaner (maybe?).
Next, wipe the Valve Plate with a tissue or paper towel wet with alcohol until you've cleaned off
all the residue. If you'd rather, just purchase new Valve Plates as they're not that expensive.
I've found that they clean up rather nicely, at least a few times before they need to be replaced.
As with the Fixing Plate, you want to remove ALL the residue to the valves will lay nice and flat
on their respected valve seats, in order to maintain a tight seal.
Nice and clean! All the residue has been removed and this Valve Plate looks good as new. If the
residue was thick, there may be some discoloration, but that will not interfer with its function.
As I mentioned earlier, you can get a pair of new Valve Plates cheaply if you'd rather go that route.
Now it's time to remove the Pump Head and clean it. You can already see the residue on the top side.
Remove the four corner screws, again, being careful not to mess them up.
With the Pump Head removed, you can see the rubber Pump Diaphragm. While you're here, take a look at
the diaphragm and make sure it's in good shape. Look for holes, torn edges, etc. They can be replaced
also if necessary, but it's a little harder to do and so far I've never seen any damage to mine, nor
have I seen one that had any solder flux residue. If you do have to replace them, you'll have to heat
up the screw first as they have Loc-Tite on them. Use your soldering iron and place it on the screw
for a few seconds, then try removing the screw. If it won't come out, try some more heat for a few
seconds more and try to remove the screw again. Repeat until the screw comes out. Hakko sells a kit
with both diaphragms and new screws with the Loc-Tite on them already.
Here's a close-up of the outside of the Pump Head ...
... and the inside of the Pump Head. You can see it's much cleaner then the outside.
Clean up the Pump Head just like you did with the Fixing Plate, using a swab and some alcohol. Use
your drill bit or other instrument to clean out all the holes too. Once the outside of the Pump Head
is clean, wipe down the inside too, making sure it's nice and clean when it's dry.
Before you replace the Pump Head, take note of the matching pin and hole. These must line up when
you place the Pump Head back on the Pump Frame or you'll have problems.
Also, make sure the Pump Diaphragm is properly seated in the Pump Frame. You want the circular edge
to look like this, nice and flat against the Pump Frame for the entire diameter of the diaphragm.
Not like this! Notice how the edge of the Pump Diaphragm is wrinkled in places, and not laying flat
on the Pump Frame along its entire diameter?
If the Pump Diaphragm is not flat along it's entire diameter, move the Pump Crank one way or the
other until you get the Pump Diaphragm to lay perfectly flat.
Now place the Pump Head back on the Pump Frame, making sure the locator pin I mentioned earlier
is lined up with the hole it goes into.
Then replace the four screws, but don't overtighten them.
Install the Valve Plate, taking care that the notch lines up with the key.
Note the locating pin on the Pump Fixing Plate and the Pump Header.
Place the Fixing Plate in position making sure the pin mates with it's corresponding hole.
Tighten the two Fixing Plate screws, being careful not to mess them up.
Pull the hose off the center port on the Back Holder. If it's gunked up, it
should be cleaned out too. Try pushing your cleaner rod in from the other end
so it'll push anything out the port tube. Cleaning the other port tube may be
tougher since it's pointing down and there's stuff in the way. The only way
to remove the Back Holder is to crack the 808 case open, which may be more then
you feel like doing.
Finally, replace the vacuum hoses, replace the pump cover, and fire it up!
You'll notice right off the bat that your 808 is now working like it did
when you first took it out of it's box.
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