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Keurig B60 slow flow problem & repair experience

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Re: Keurig B60 slow flow problem & repair experience

Postby GetSet » Sun May 05, 2013 11:57 pm

Glad to hear that you got yours working – that was a tough one. The internal leakage of the solenoids is sure worth noting. Sounds like EmmJayEff was looking in the right direction on that one. The reason I was asking about whether the cup sizes were correct was that I was wondering whether there was another leakage path on the water input side – either through the water pump check valve or through the aft valve, even though I know you replaced it. So during brewing some of the water would come out of the K-cup arm, and the rest split and be forced through a leackage path back into the external water reservoir. Still, if the reservoir level rose slightly during brewing, I think you would have noticed it. This was just a long shot in case EmmJayEff’s idea didn’t work out.

When I repaired my B66 I noticed that the aft solenoid shorted out, but it only showed a small amount of corrosion, and not even close to enough to leak even a drop. These things can be tricky. It was even more tricky that it sounds like yours leaked more or less depending on your usage cycle or assembly/disassembly activity.

Unfortunately, I have never tried the EZ-Cup, and I don’t remember hearing the air pump cycling completely on-and-off. The only thing I have ever heard from my air pump is the gentle, quiet ticking noise during brewing, which I assume is due to the pulse duty cycle that is driving it, and also the revving up at the end of the brew cycle to “blow out” the remaining coffee in the cartridge. I did have fun experimenting with a B70 one time though. In the “Keurig Experiments” document that I posted, I tried a couple of things that might have come close to simulating a heavy load. When I blocked (pinched) the K-cup arm tube, the machine just kept trying to brew and didn't quit. I eventually had to let the machine win when my fingers just go too tired to pinch it anymore. Another time, I pinched, but didn’t block the K-Cup arm tube. I then varied the amount of constriction. To my surprise the air pump didn’t speed up in response to more constriction. We thought this should happen, but it didn’t. It might be that the duty cycle of the drive current changed, but I didn’t hear the difference. In retrospect, I should have measured the drive waveform with an oscilloscope to see, but the machine belonged to somebody else and I needed to return it at some point. :wink:
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Re: Keurig B60 slow flow problem & repair experience

Postby atembedded » Thu May 09, 2013 10:10 pm

I also tried the "cafe cup" brew insert. It was slow in filling my cup, and sometimes quit before it was full. I tried the one that came with the machine, and it works a lot better. I just use it now.

About the air pump drive. You might try just making a 555 50% duty cycle drive hooked up to a n chan mosfet and drive the air pump that way. There's probably a signal to turn the pump on and off that you can use to start and stop your drive circuit. You can change the frequency and duty cycle as much as you want. I don't know how that will affect the pressure sensor. Anyway, you might be able to generate enough pressure to get your cup filled. BTW, sciplus is out of the solenoid valves. I'm sure mine came out of a Kuerig of some sort. I still have 4 left.
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Re: Keurig B60 slow flow problem & repair experience

Postby atembedded » Thu May 09, 2013 10:46 pm

I just looked at the pressure sensor circuit referenced earlier in this thread. If you can, look at the voltage between JP33 and J17-9 when the pump is running. This is the amplified sensor output. The values on the schematic are with the pump off, so they don't give any info about the voltage you need to know. Perhaps you can put a voltage divider between the left side of JP33 left open and J17-9 and run the lower voltage to the right side of JP33. So, it would be say Left JP33 -> 50K OHMs-> Tap to Right JP33 -> 50K OHMs -> J17-9. That will reduce the output by half, and maybe the pump will work harder.
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Re: Keurig B60 slow flow problem & repair experience

Postby dweeezil » Tue May 14, 2013 8:32 am

I've been letting my machine "just work" for the past week or so and it seems to be very solid at this point. I'm going to live with the occasional "pulse on and off" which only seems to happen when I use the EZ-Cup insert.

Thanks for the information, atembedded, regarding the mods and information to what I think can best be called the pump pre-amp circuit. I don't think there's any question that it would be possible to get the pump to work harder because, as I mentioned, it clearly goes into what is probably a 100% duty cycle mode during the "air puff" completion of a normal brewing cycle.

I am slightly concerned that I don't have the pots on the upper board set correctly, but it seems that their main function has to do with allowing the sensor to properly detect the sudden drop in pressure that occurs when the pump starts sucking air.

Again, however, the overall brewing quality now seems to be very good and I'm quite happy with the performance of the machine. It's fairly clear to me that the design of the brewing cycle is to regulate the pressure to offer a slow-but-sure flow of water over the grounds to ensure they're all steeped properly. If the water were forced through the grounds too quickly, the brew strength would be weakened due to less contact time.

I do have a few lingering questions about the design of the brew cycle. For one, I'm curious as to how the need to de-scale is determined. I'm interested in the results of your experiment, getset, where you pinched the outlet hose to simulate a high-load brew. I would have expected the brewing cycle to eventually time out and, possibly, for it to indicate the need to de-scale at that point. Another question is exactly what kind of motor is used to drive the pump. Given how cheaply they appear to be and that there are only 2 wires feeding it, I suspect it's a permanent magnet brushed DC motor. From what I've read, the computer must be trying to maintain a slow-but-steady brewing cycle by maintaining a constant pressure in response to different brewing loads. I've noticed the sound of the pump motor is similar during the start of the brew cycle as it is during the air-puff phase at the end. It would be during these times that it's using close to a 100% duty cycle. Once the brewing cycle is going, if it's trying to maintain a constant pressure on the input side, pinching the output tube would cause an increase in pressure which would signal the computer to back off on the duty cycle, whereas releasing the tube would lower the pressure indicating more torque is needed.

There are only two sources of feedback available to the computer during the brewing cycle: the pressure in the input side of the circuit and the overall brewing time. The system has no way to (directly) detect leakage on the input side (the source of the problem in my case) nor an abnormal blockage on the output side. Too bad I got rid of my oscilloscope years ago when I left the electronic service industry because it would certainly be interesting to observe the waveforms in response to varying inputs.

Keurig appears to have designed a system to provide a constant brewing flow at the lowest possible cost. The obvious improvement would have been to add a pressure sensor to the output side of the system. That would have allowed the controller to make more intelligent decisions and would have allowed several failure modes to be directly detected.

My main question at this point is whether I'm going to keep the machine plugged in 100% of the time. The aft solenoid has water contact by design and the front solenoid seems to get a little water as well. Both will ultimately fail again. I don't have any more spare ones and it's unfortunate that sciplus is out of them. If it turns out that I've extended the life of my machine by another year or so, I'll be pretty happy. It's about 4 or 5 years old already and sounds like it has lasted a lot longer than many other people's machine. We've always kept the machine plugged in and powered on which I do think has a couple of hidden benefits: first, since a full heat-up from room temperature to the brewing temperature is never needed, the aft solenoid's venting function never really comes into play. Second, the heat within the machine will evaporate any water that happens to leak more quickly.

I'd like to thank everybody, once more, for the great feedback and for all the other information available on this list. Hopefully this thread only adds to the utility and can help someone else in the future.

- Tim
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Re: Keurig B60 slow flow problem & repair experience

Postby desulfator » Tue May 14, 2013 11:00 pm

-

My question is whether this cycling of the air pump is a normal part of its operation during brewing cycles which require maximum air pressure?


Air Pump voltage readings suggest the micro is closely controlling the air motor.

Air motor startup (brief only a second or so)
11.84v either condition

Brew Voltages
4.90 With a K-Cup
4.62 Discharging hot water (no cup)

Cup Blowout Voltages
8.61 With a K-Cup
8.64 Discharging hot water (no cup)

Pinching the air tube results in weird readings.

I've noticed that when the brew cycle starts, the air motor gets 11.84v for about 2 seconds then the voltage is cut for a few seconds. I suspect after getting a 11.84v start the air pressure goes beyond the limits so the micro kills the power to the air motor until the pressure reduces. Once the pressure reduces it is driven at the 4.??v level until the pressure drops (cup is empty) and then gets a final 8.6?v to blowout the cup.

You may be able to extend the life of your Keurig by replacing the solenoid valves with a Normally Open, 12vdc valve.

My B70 occasionally delivers a short cup. The problem was traced to the front solenoid valve.

I did an Ebay search for,
open 1/4 solenoid valve + (12v,"12 volt")

So I ordered the following 1/4 inch valve. Adapters will be needed to reduce the port size to 3/16 inch.

Image

It will require that I reverse the signal to the valve by using a $1.25, 12vdc, SPDT 10A relay.
http://www.mouser.com/Search/ProductDet ... E-1-VDDC12

The relay will be connected to the solenoid valve circuit. The NC contacts will operate the N.O. valve when the solenoid circuit is de-energized (venting the boiler during fill-up). The solenoid circuit will be provided it's own ground.

So when the Keurig micro applies voltage to the solenoid circuit, the relay will switch the solenoid to the N.O. contacts and allow the solenoid to remain dormant in it's N.O. state. When the Keurig micro kills the power to the solenoid circuit the relay provides 12v through the NC contacts and the valve has it's own ground to complete the circuit.

The relay will take the beating of being energized most of the time. The solenoid valve will vent until it is called upon to close during a brew with the air motor pumping out the boiler.

I still have to check to make sure I am not overloading anything. The FET driver can sink 680ma. The relay I am going to use only draws 33ma. I won't know what the current draw is on the 1/4in valve until I receive and measure it. Hopefully it is within the capabilities of the FET driver circuit.

More on this later. :)

-
Man opens a banana by hacking away with every sharp object he can think of.
Monkeys open a banana by merely pinching the end opposite of the stem with their fingers.
-
Who is better at problem solving??
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Re: Keurig B60 slow flow problem & repair experience

Postby dweeezil » Sat May 18, 2013 8:33 am

desulfator wrote:Air Pump voltage readings suggest the micro is closely controlling the air motor.

Air motor startup (brief only a second or so)
11.84v either condition

Brew Voltages
4.90 With a K-Cup
4.62 Discharging hot water (no cup)

Cup Blowout Voltages
8.61 With a K-Cup
8.64 Discharging hot water (no cup)


Those numbers totally jive with my observations of the machine. In particular, the start-up clearly has the biggest "kick" which is clearly audible during the beginning of the brew cycle. I only took measurements for a brief while and was only interested in the brewing voltage but I'm quite certain it was in the 5V range.

Another interesting point regarding my experience is that it seems the original Keurig air pumps are quite reliable so long as they don't become corroded. The B60 design wins big time in this category over the B70 since the pump is totally shielded. I was lucky to have a spare from my parts machine to try. I was also lucky that I didn't damage the internal membrane when I had disassembled them to look for damage because it looks to be pretty fragile. I was tugging at it quite a bit looking for any signs of tearing or holes in the rubber.

That's a pretty nice solenoid you found. I presume it will fit in the space of the existing ones? It looks to be a bit wider. I like the idea of having the solenoids not powered all the time; the "inverter" relay ought to be able to take the heat of being energized almost 24/7 with no problem. I'll be interested to hear how things go this this component.

- Tim
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Re: Keurig B60 slow flow problem & repair experience

Postby GetSet » Mon May 20, 2013 12:34 am

Nice! It sounds like you may have a good alternative for the valve that looks to be higher quality. I also follow your idea of using the relays to reverse the logic, allowing the use of normally open relays.

I don’t think anybody here had done air motor voltage readings of those steps in the brewing process yet. What you did should come in handy. I do have an oscilloscope that could reveal some more information about the duty cycle, but right now I don’t have any Keurig units open to experiment with or make measurements on. I returned the B70 to the person who owned it and my B66 has been working so well that I just haven’t had it open for several months. That’s why I haven’t been able to repeat any experiments lately, so I haven’t been able to confirm anything more about those two experiments that I mentioned in my post back on May 5th other than what I stated there at the time. Like you, dweeezil, I would have expected the brewing cycle to eventually time out when totally blocking the exit arm tube, but after three minutes or so, I couldn’t continue to hold it. Also, partially pinching this same tube and varying the amount of constriction didn’t seem to make the air pump react any differently at the time, but I was judging this based entirely on the sound of the air pump. A more thorough approach would have been to either measure the duty cycle with an oscilloscope, or just use a voltmeter to measure the average voltage like desulfator did. The outcome of those and other experiments I did is posted on Page 16 of the “Dissassembly + Repair Guide - Keurig B70 Platinum” thread, but here are both documents again for reference:

https://www.dropbox.com/s/k2pxxhdawc3g1xj/Keurig%20Problems%20and%20Causes.pdf?m
https://www.dropbox.com/s/18oru4uoyy72r18/Keurig%20Experiments.pdf?m

These are both the “Keurig Problems and Causes” and the “Keurig Experiments” documents. Please let me know if anybody has trouble opening these.

Right now I don’t recall whether or not anybody has posted any theories about how the Keurig determines when de-scaling is needed. I just wondered whether it might make this assumption if it fails to get signals from one of the various level probes in the hot water tank at times when it expects to see them. Worst case, if it doesn’t get any signals from any probes at all, my theory is that there is nothing to stop the water from overfilling the tank during the initial filling stage. In fact, the water will keep right on going through the air ventilation tube at the top, through the mesh filter and aft solenoid valve. From there it will split and either exit out the overflow tube back into the reservoir, or get sucked into the thin tube that goes to the input side of the water pump, because it is still running and there is suction there. Meanwhile, the water shouldn’t push into the air pump or pressure sensor tubing, because these are dead ends since their ends don’t allow air to escape. However, the water will push on the AIR that is trapped in these tubes. This creates a small increase in air pressure that registers in the pressure sensor. Any increase in air pressure during this stage is a signal to the processor that something is not normal, so it stops the tank filling. Since it has no way of knowing how full the tank really is at this point, it assumes that it is pretty full and requires you to use the next to the largest setting to get rid of it. At the end of all this, maybe it assumes that de-scaling is needed.

Concerning the availability of the original valves, I’m confused, because sciplus.com actually does show that they have the valves in stock, Item# 40672P1. You just can’t use “Keurig” as a keyword to find it. Also, AllElectronics.com has availability of the valves in stock, CAT# SOL-132. SkyCraftSurplus has availability for the air pumps and water pumps, but they have been out of stock on the valves for a couple of months now. Mpja.com has availability for the air pumps. I got all of these leads from various people on the B70 thread.
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Re: Keurig B60 slow flow problem & repair experience

Postby Moon Unit » Sun May 17, 2015 8:40 pm

dweeezil wrote:I finally decided to disconnect the front solenoid completely and manually operate the tube with a small clamp during the brew cycle by letting it open during the topping-off phase and then by pinching it during the brewing phase. Eureka! It brewed just fine. The front solenoid must have had an internal leak (inside its body) rather than simply letting some pressure leak past the internal seal. I think this is a very important failure mode to consider when repairing a machine.

As I said, I feel rather stupid for not catching this earlier; even if only accidentally. I had gotten 2 replacement solenoids but only replaced the aft one (which doesn't really even matter much for the proper operation of the machine) and ignored the front one because it showed no obvious defects. My original intent was to simply replace both of them, regardless, but I got lazy and skipped the front one because it looked so clean.

The lesson here is that the solenoids can leak internally into their body and that can't be detected by pinching off the output side.

- Tim


What a great thread this is and I wish I would have found it earlier. After a long uphill battle the problem with mine was also due to an internal air leak on my solenoid which I eventually found by accident.

Last Thanksgiving (2014) I was at my sisters house and she was throwing away her B66 which was dribbling and not filling the cups anymore. After reading/watching tons of mostly wrong information on the Internet I started digging in to it. Mine is an older unit which only has one solenoid and seemed pretty straight forward. Let me also say there have been many false successes as listed in this thread which kept me going in circles. Like it would always work well for a while after being turned upside down. So I got it all apart and the only thing that I noticed was a little water in the tube coming from the air pump and a little moisture in the pump itself. Of course it worked well after being upside down so I thought that was the problem and put it all back together. After a few days, back to the dribble and the case comes off again. This time I'm smarter and leave the case off, and it's still off as I am writing this and I became obsessed over getting this thing working again.

I was 100% sure that the solenoid was OK because when it was dribbling I tried closing off the overflow tube back into the tank numerous times with no improvement and started thinking electrical problems. I scoped the motor and saw that the speed was controlled by PWM at about a 50% duty cycle during brewing. And of course it worked perfectly on the bench. To keep from having a big scope on the kitchen counter I left the cover off of the main circuit board and kept tabs on the motor output with a voltmeter and I got pretty much the same voltage readings as in this thread but they were not changing when working OK or dribbling. So then I tore into the top board thinking the pressure sensor had a problem. It was a real cluster for a while with both the main board and top board just hanging by the wires and still making coffee by carefully pushing on the little switches and being blinded by the three very bright blue LED's.

So, about a month ago my solenoid stopped working (thank goodness) and the coil was reading open. No problem, I gotta have my coffee so I bypassed the solenoid and just plugged the hose with my finger, imitating the timing of the processor. It was pretty difficult to get the timing right because a few seconds after it starts brewing the solenoid opens and then immediately closes within about 50 milliseconds or less. I guess the pressure sensor is looking for a pressure drop and if it doesn't see it at the right time the brewing will stop.

Anyway, because of laziness and disgust over this machine I operated it this way for close to a month before ordering a new solenoid. After a few days I noticed that the machine is working remarkably well and continued to do so for the entire time with out a single dribble. I started back to thinking of electrical problems but nothing that I could make any sense out of. I installed the new solenoid a few days ago sorta expecting the problem to return but it didn't.

I saw this thread today and luckily the old solenoid was still in the trashcan so I took it apart. Sure enough, the case had a hairline crack on the pressure side and now after all of these months I will be able to put all of the covers back on with no more drama!!!!!!! :mrgreen:

One thing that I want to mention, with my machine at least. I have been monitoring the voltage/duty cycle to the motor all of this time and it never changes during brewing regardless of back pressure. No K-cup, lights, bolds, it always holds steady. Sometimes during the bolds the motor will cycle off and on but the duty cycle never changes. I think the pressure sensor does offer some pressure feedback but on my model I think the main purpose is to sense the end of the brew cycle and maybe a safety feature in case of a clog in the system.
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Re: Keurig B60 slow flow problem & repair experience

Postby bogiesan » Mon May 18, 2015 9:50 pm

Thanks for your contribution to the Keurig repair community. Please stick around!
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Re: Keurig B60 slow flow problem & repair experience

Postby Gordon » Sun Mar 26, 2017 12:21 pm

I just created an account and wanted to jump in here. I have a B70 that was working totally fine without a pod, but with a pod it would be a slow dribble. I might get a half a cup or a quarter of a cup and it would take 3 minutes or so to do that. I followed this "Disassembly Guide" on another post: http://www.singleservecoffeeforums.com/dissassembly-repair-guide-keurig-b70-platinum-t8124.html.

I didn't need to do the full disassembly, because my problem ended up being that there was a small leak in the hose part that connects to the piercing needle. Unfortunately since I was following the guide my machine was in pieces by the time I realized. I ended up re-assembling it and just leaving the top of the pod part off.

This is the issue and my temporary tape repair:
http://imgur.com/a/WEdxK

Here is a video of the leak: https://youtu.be/eUepgzJX1-8

Hopefully this helps some one!
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