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Dissassembly + Repair Guide - Keurig B70 Platinum

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Keurig B70 Platinum Malfunction - water heater never shuts o

Postby CoglFin » Tue Apr 28, 2015 6:39 pm

I did a lot of searching, looking for some help with my problem, but it seems that overwhelmingly the posts about the B70 have to do with malfunctioning solenoids (doesn't fill the cup, sends water back to the exterior reservoir, etc.). This site was very helpful in getting me started, dismantling the B70 shell so I could get a look at the insides, so I thought this would be a good place to post my problem and what I did to fix it.

This B70 was purchased in Nov. 2011, although based on several dates on the interior of the unit it was built in early/mid 2010.

Problems: (All these occurred together, and started in the middle of the night when the unit was turned off, but plugged in)
1) Unit starts to heat as soon as it is plugged in, even if not turned on. If left long enough, it will start spewing hot water out of the delivery line (in the arm that holds the coffee container) and often spews hot water out of the overflow line going back into the external (normally cold) water reservoir. Cannot be stopped from heating by turning on/off, or by “resetting”. Can only be stopped by unplugging from power.
2) Unit turns on as soon as plugged in, about 50 – 70% of the time. When this occurs, it will not turn off with the rear toggle (“power” switch). Display can be turned off by “resetting”; e.g., press and hold left/menu/right buttons simultaneously until display goes out. Once this is done, the rear toggle switch behaves as expected, BUT see the next problem.
3) When the unit is on, it frequently locks up. I.e., the display goes blank except for saying “NOT READY”, none of the buttons do anything, the blue LEDs in the cold water tank go out, and the rear toggle switch does not work. Resetting (see above) gets it back, although it may lock up again 10 seconds later.

Note: IF it stays on and does not lock up for long enough (about two minutes), it goes “Not Ready” to “Ready”, and will brew a normal cup of coffee. All the buttons appear to work normally (e.g., allows selection of all options, brews the proper size of coffee per the selection on the front panel, etc.). However, heater never turns off (you can hear it heating).

Cause: The water heater coil was shorted to the metal body of the hot water reservoir (inside the unit). If you've taken one of these apart, you have probably looked at the bottom of the hot water reservoir, where the two leads to the heater coil come out. Apparently mine shorted very close to the neutral end of the heater coil. The circuitry is designed such that the 110V AC load line is always connected, and when the proper water temperature is reached the circuitry opens the connection to the AC neutral line, thus depowering the heater coil BUT LEAVING IT HOT (electrically). So when the neutral end of the heater coil shorted to ground, the heater coil was always fully powered with 110V AC. After my repair, I have experienced none of the other problems above (but I listed them in case anyone is searching on them). I suspect they were a result of the heater immediately drawing full amperage before the CPU and other control electronics could power up and "settle down".

Solution: Purchased a used but working water heater on eBay. It was several years newer and the plastic top was a slightly different configuration than mine, but I put the new metal heater coil base and the old (original) plastic top together and installed that. Everything is now working fine.

In the process of testing everything between AC power and the heater coil, I generated a partial schematic of the B70, detailing the power and control circuits for the water heater. If anyone has a similar problem and would like to take a look, let me know and I'll post the schematic.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby njchoochoo1 » Sat May 02, 2015 4:00 pm

GetSet wrote:Welcome njchoochoo1. Do you have an older unit (B70 Platinum, B60, etc.), or one of the newer units from within the past year or two?


I have a B70 Platinum that's roughly 3-4 years old. Just today the machine started to make a 1/4 cup of coffee when the 12oz. selection is made. I descaled it about a week ago and was doing another one when the 1/4 cup issue started. The motor turns really fast for 5-6 seconds, and then it starts to draw water in REALLY slow. I don't know if replacing the solenoids and the few other parts I've read about will fix the issue. I am no good at soldering so any replacement parts have to be plug and play. :)
Any assistance is appreciated. Thanks.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Mon May 04, 2015 8:47 pm

Sounds like that was a tough one, CoglFin. I never heard of a hot water heater coil getting shorted like that before, but it could have happened to a few people that never did figure out what their problem was. Your theory of how it confused the CPU sounds pretty reasonable. It could also be because of the high current running through the safety ground. I am assuming that when the heater coil shorted to the metal body that it was ultimately completing the (bad) circuit through the safety ground. The safety ground isn't supposed to carry that kind of current, normally. When it does, it might throw off some of the CPU and other electronics that are relying on the safety ground for their signal reference. Right now that's just a theory; I haven't actually traced the wiring through to see whether the safety ground is actually used that way or not. Anyway, that was a good catch and a well deserved victory. When you get a spare moment the partial schematic you came up with might be of some value here, since we don't yet have a schematic of that part of it. I drew up a quick sketch of the EMI (power conditioning) filter circuit board myself at one time, because of questions about whether the transient suppression on it could cause some problems if it shorted. I'd say don't worry if it's just hand drawn - hand drawn is better than nothing.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Tue May 05, 2015 12:03 am

njchoochoo1:
While the water is being drawn from the external water reservoir, is any water dripping out of the K-Cup arm?
Does it ever give you a message that it needs to be re-primed?

You probably already checked these, but you might try:
- Re-seating the water reservoir.
- Remove the charcoal water filter inside the reservoir (if any), and see if water gets drawn in any easier without it.
- When you remove the water reservoir, there is a plastic grid in the opening that functions as a kind of coarse filter. Make sure it doesn't look blocked by anything.

There is a one-way check valve between the water pump and hot water tank. It may be sticky. I don't know of a way to clean it directly without disassembling the unit and using a Q-tip on it. De-scaling may help it somewhat, but you already tried that.

Also wanted to mention that the water pump that draws water in from the outside reservoir is different from the pump that pumps the coffee into the coffee cup - they are two separate pumps. The latter is actually an air pump.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby njchoochoo1 » Tue May 05, 2015 1:57 pm

GetSet wrote:njchoochoo1:
While the water is being drawn from the external water reservoir, is any water dripping out of the K-Cup arm?
Does it ever give you a message that it needs to be re-primed?

You probably already checked these, but you might try:
- Re-seating the water reservoir.
- Remove the charcoal water filter inside the reservoir (if any), and see if water gets drawn in any easier without it.
- When you remove the water reservoir, there is a plastic grid in the opening that functions as a kind of coarse filter. Make sure it doesn't look blocked by anything.

There is a one-way check valve between the water pump and hot water tank. It may be sticky. I don't know of a way to clean it directly without disassembling the unit and using a Q-tip on it. De-scaling may help it somewhat, but you already tried that.

Also wanted to mention that the water pump that draws water in from the outside reservoir is different from the pump that pumps the coffee into the coffee cup - they are two separate pumps. The latter is actually an air pump.


GetSet,

There is no water drip and I have never received a prime message from the machine. I did try all of your suggestion short of taking the unit apart and Q-tipping the check valve. I did unplug the unit for a few minutes and am now able to get a full cup of coffee, but it still takes significantly longer to draw water out of the tank than it used to. Thanks again for your assistance.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Fri May 08, 2015 6:23 pm

I’m not sure what else it could be at this point besides either the check valve or the water pump itself. People here have mentioned more problems with their check valves than with their water pumps, but I wouldn’t want to discount the water pump. EmmJayEff said that it is driven by “A 0 to 12 Vdc square wave signal with a specific duty cycle” rather than by simple continuous DC. The square wave signal may be Keurig’s attempt to control the speed of the water pump according to who knows what conditions – hard to say. I can’t imagine any reason at all to control the speed of the water uptake. To me, faster is better. EmmJayEff did say that the duty cycle was continuous, so the speed isn’t being controlled under any typical conditions we know of. The air pump that pumps the hot coffee into the cup is a different story. The duty cycle it is being driven by varies, so it’s speed and power are definitely being controlled. Not that I'm saying the air pump is your problem, I just thought I'd mention it.

I kept wondering whether the aft solenoid valve on yours might be stuck closed. But, I keep coming back to the simple fact that if it is stuck closed, water should be coming out of the K-cup dispenser arm during the filling cycle, at the same time the water is being drawn from the outside reservoir into the hot water tank (this is because the air would be trapped in the hot water tank and can’t escape to let the water in). See EmmJayEff’s diagram at http://home.comcast.net/~michael.flynn3/Keurig/KeurigB70_TheoryofOperation_072112.pdf to help visualize this. However, if both the aft valve valve were stuck closed, and the K-cup dispenser arm were clogged as well, then that combination might make the water pump run slower. You might make sure both the top and bottom needles in the arm are clear.

If you did need to disassemble the B70 and get inside to clean the check valve, it may not mean disassembling the whole thing. You should only need to open up the bottom to get to the water pump. After loosening the water pump and disconnecting it, you should be able to get into the check valve with a long Q-tip. Note that some later models have two check valves in parallel (Gee, I wonder why?). Here is a picture of the bottom that n8dawg posted previously:

Image

Up to that point, the disassembly is not that bad or time consuming. To go much further, the snap clips in the top are the real challenge. The water pump is shown right in the middle of this picture. The check valve is hidden behind the water pump.
-
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby njchoochoo1 » Sat May 09, 2015 11:10 am

GetSet wrote:I’m not sure what else it could be at this point besides either the check valve or the water pump itself. People here have mentioned more problems with their check valves than with their water pumps, but I wouldn’t want to discount the water pump. EmmJayEff said that it is driven by “A 0 to 12 Vdc square wave signal with a specific duty cycle” rather than by simple continuous DC. The square wave signal may be Keurig’s attempt to control the speed of the water pump according to who knows what conditions – hard to say. I can’t imagine any reason at all to control the speed of the water uptake. To me, faster is better. EmmJayEff did say that the duty cycle was continuous, so the speed isn’t being controlled under any typical conditions we know of. The air pump that pumps the hot coffee into the cup is a different story. The duty cycle it is being driven by varies, so it’s speed and power are definitely being controlled. Not that I'm saying the air pump is your problem, I just thought I'd mention it.

I kept wondering whether the aft solenoid valve on yours might be stuck closed. But, I keep coming back to the simple fact that if it is stuck closed, water should be coming out of the K-cup dispenser arm during the filling cycle, at the same time the water is being drawn from the outside reservoir into the hot water tank (this is because the air would be trapped in the hot water tank and can’t escape to let the water in). See EmmJayEff’s diagram at http://home.comcast.net/~michael.flynn3/Keurig/KeurigB70_TheoryofOperation_072112.pdf to help visualize this. However, if both the aft valve valve were stuck closed, and the K-cup dispenser arm were clogged as well, then that combination might make the water pump run slower. You might make sure both the top and bottom needles in the arm are clear.

If you did need to disassemble the B70 and get inside to clean the check valve, it may not mean disassembling the whole thing. You should only need to open up the bottom to get to the water pump. After loosening the water pump and disconnecting it, you should be able to get into the check valve with a long Q-tip. Note that some later models have two check valves in parallel (Gee, I wonder why?). Here is a picture of the bottom that n8dawg posted previously:

Image

Up to that point, the disassembly is not that bad or time consuming. To go much further, the snap clips in the top are the real challenge. The water pump is shown right in the middle of this picture. The check valve is hidden behind the water pump.
-


GetSet,

My thanks for you taking the time to respond. I will try to clean the check valve and see if it helps. I actually called Keurig and they were willing to sell me a 2.0 comparable to my model B70 for $159 since they were unable to rectify the issue. I'll get this running right I think. Thanks again.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby CoglFin » Tue May 19, 2015 5:02 pm

GetSet wrote:Sounds like that was a tough one, CoglFin. I never heard of a hot water heater coil getting shorted like that before, but it could have happened to a few people that never did figure out what their problem was. Your theory of how it confused the CPU sounds pretty reasonable. It could also be because of the high current running through the safety ground. I am assuming that when the heater coil shorted to the metal body that it was ultimately completing the (bad) circuit through the safety ground. The safety ground isn't supposed to carry that kind of current, normally. When it does, it might throw off some of the CPU and other electronics that are relying on the safety ground for their signal reference. Right now that's just a theory; I haven't actually traced the wiring through to see whether the safety ground is actually used that way or not. Anyway, that was a good catch and a well deserved victory. When you get a spare moment the partial schematic you came up with might be of some value here, since we don't yet have a schematic of that part of it. I drew up a quick sketch of the EMI (power conditioning) filter circuit board myself at one time, because of questions about whether the transient suppression on it could cause some problems if it shorted. I'd say don't worry if it's just hand drawn - hand drawn is better than nothing.


GetSet,

I believe all the grounds are interconnected, so your theory also is reasonable. I looked around, but don't see any instructions on how to upload attachments. If someone can give me some instructions, I'll upload the partial schematic I have.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Thu May 21, 2015 10:37 pm

You can't actually upload any attachments onto this forum, since there is no storage space here. People have posted images here, typically by setting up their own Photobucket account and then uploading photos to it. When they return back here and write a post, they then refer to it in their post using the Img tool to link to the photo, which makes it appear here. Documents are different. You sign up for some cloud account like Drop Box, store your document there, and then refer to it in your post with the URL tool. So it depends on whether your schematic is hand sketched (which you would probably take a photo of or scan in), or produced in some drawing program and made into a PDF (which you would store on Drop Box or similar).
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby CoglFin » Mon Jun 01, 2015 11:49 am

GetSet wrote:You can't actually upload any attachments onto this forum, since there is no storage space here. People have posted images here, typically by setting up their own Photobucket account and then uploading photos to it. When they return back here and write a post, they then refer to it in their post using the Img tool to link to the photo, which makes it appear here. Documents are different. You sign up for some cloud account like Drop Box, store your document there, and then refer to it in your post with the URL tool. So it depends on whether your schematic is hand sketched (which you would probably take a photo of or scan in), or produced in some drawing program and made into a PDF (which you would store on Drop Box or similar).


OK, here's my third try at this. Took some time to figure out how to get it to fit on the forum screen. You will probably have to make your browser full screen. If it still doesn't fit, right click on it and open in a new tab, or copy and paste it into an editor, document, etc. It is apparently all there, even if it gets cropped by the forum screen. If I make it much smaller, the quality starts getting pretty bad.
Image
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Tue Jun 02, 2015 2:04 pm

Hey thanks! The maze of wires is explained! You filled in a bunch of information that was missing here. This will help. It does show that the driver board is connected to safety ground, which answers a question that I had mentioned earlier. Plus, you've got part numbers that people can order replacements from.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby Sailorsteve » Wed Aug 12, 2015 7:45 pm

So I've read the thread and found some very useful info here! Thanks!
My machine was doing the brewing continuously thing and after replacing both solenoids on my B70 it worked - except for several "new" problems
1. When the READY TO BREW comes on I lift and reclose the K-cup holder (simulating installation of a K cup) and then reclose it. The blue light around the button flashes. When I select the size, and push the blue flashing button the machine water pump turns on and fills the reservoir. When the water gets to the set heighth, the pump turns off and the air pump kicks on - voltage to the pump is 12+ VDC. After a few seconds the pump voltage drops to 5 ish VDC and the flow drops dramatically! It takes for ever to fill the cup - even without a K cup installed.
2. Once the level of water in the boiler finally drops (sometimes so far that air from the pump flows straight through the boiler and out the discharge!) But if it does stop - the solenoids both seem to click and the machine just sits there! It doesn't go into a refill, reset type situation as it used to do. It use to finish filling a cup to desired level then the air pump would blow the line clear, turn off, then the water pump would turn on and refill the boiler making it READY again. NOT ANYMORE!!!!!
3. Filling a cup to the set level is erratic sometimes.
I have taken the pump apart and it seems to be working fine - no clogs or visible corrosion.
I've read about a voltage regulation of the air pump voltage based on pressure going to a sensor of some sort but I am unclear on the actual process by which it works. Does it VARY pump speed via voltage drop constantly or is it a timed event where the pump initially turns on at a high speed to get the water moving then slow down? OR Does it start out higher speed and stay there as long as it is overcoming back pressure from the K Cup?
I have tried pinching the hose going to the circuit board behind the display. The air pump momentarily speeds up then shuts off! Again, not clear on the control functions of the pump controller.\
Any help or insight would be much appreciated!! Thanks!
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby GetSet » Fri Aug 14, 2015 11:21 pm

I don't have a Keurig apart right now to measure the voltage on the air pump, but according to EmJayEff the air pump is driven by a 12 VDC square wave of varying duty cycle. From what I hear when listening to mine, it is normal for the air pump to run fast at the beginning of the brewing cycle, which kind of boosts the pressure when the cup first starts to fill. During the rest of the time the cup is filling, the air pump is running kind of slow. After the water level in the water heater goes below the height of the outlet hose, air starts to escape. The air pressure sensor senses this change in pressure and boosts the speed of the air pump again to blow the remaining water out of the K-cup to clear it. Then the brewing ends and the top-off begins. In my experimenting with the air pressure sensor, when I blocked it to prevent it from sensing this change in pressure at the end, the air pump speed doesn’t increase like it normally does. Instead it continues to run slowly for a long time, then eventually times out and goes back to the “READY TO BREW” display. So I guess what I'm saying is that the 12VDC you measured in the first few seconds, and the drop to 5 VDC later, is probably expected, although I've never measured it to confirm it. The 5 VDC is probably a result of the duty cycle being deliberately weakened to make the pump go slower during most of the brewing time. I'm assuming you are using a regular voltmeter that would average out this square wave thing into an average reading of 5 VDC.

I know you have replaced both valves, but it still wouldn't hurt to check 2 things:

1. During the brewing cycle, put your finger over the overflow tube opening (above the water reservoir) to block it. If the water dispenses faster from the K-cup arm, then the aft valve is stuck open. Maybe the driver board is mistakenly keeping it open when it shouldn't be. Which leads to #2:

2. During the brewing cycle while dispensing, measure the voltage being applied to each solenoid. They should both be 0 VDC during this time. This keeps them both closed.

The fact that you can get a reaction from the air pressure sensor by pinching it's hose is encouraging. At least it is responding as if it is alive. From what I wrote down when I did that, it sounds like about the same thing happened on mine.

Other than that, I don't know much more about how the air pressure sensor is used. I did block the K-cup arm once to see what would happen. I would have predicted that the air pump would speed up in response to more constriction (blockage) of the K-cup arm output, but it did not. Speeding up the air pump control would have compensated for blockage by applying more pressure to push the water out.
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby Losada24 » Sat Aug 22, 2015 3:29 am

Nothing say about this Repair Guide its absoultly Awasome! :) Keurig B70 is the best coffeemaker i have ever seen before. This Post has contain the ultimate guide of repairing. "GetSet " CAN YOU Provide Some HD Pics I want to Use this in my blog at- http://coffeeable.com/
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Re: Dissassembly + Repair Guide - Keurig B70 Platinum

Postby PUDGI300 » Tue Sep 15, 2015 9:22 pm

A lot of good posts here. Most of the common problems have been covered. I started with the not full cup and the air pump seems to have solved that. Now i have a new problem on the B70. The machine is sitting there ready to brew and out of the blue it will dump about 4 oz of water out the kcup spout. Sometimes it will do it once or twice an day . I have changed both solenoids and the air pump. Could i have gotten a bad air pump? Hope someone lead me in the right direction.
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