"Hottop Bean Roaster" Unofficial FAQ
by Randy Glass - Copyright 2003-2011 - All rights reserved
E-mail me at firstname.lastname@example.org
The following information has been assembled from my personal experience with the Hottop Bean Roaster along with information gathered from the Internet as well as questions and recommendations from other users of the Hottop Bean Roaster submitted to me. This information is presented as is, where is, and no warranty of applicability, safety, or usability is offered nor inferred. Some of this information may actually be dangerous, could cause physical injury or property damage or worse, and some of it could easily void your warranty if one is still in effect. Use all the following information at your own risk. The Feather River Canyon News, the author of this information, and anyone else who may be involved with this website accept no responsibility or liability for this information, its accuracy, or how it may or may not be used or interpreted by you, your neighbor, or anyone else living or otherwise. Reading and/or making use of any on the information on this page or on any pages linked herein is your acceptance that you are totally responsibility for any and all damages or injuries that this information may cause.
Be aware that the information contained herein coveres a number of different models and design changes over a period of years. Not all of these problems and/or solution necessarily apply to your model of roaster. If you have any questions about the information in this page contact me. If you need further assistance try HottopUSA for parts replacement, technical aid, or warranty work.
1) What's the fastest way to start another roast in a hot machine?
The idea is to get the machine cooled off after finishing one roast and before starting the next. Of course, you can just start the subsequent roast and allow the machine to go through it's cooling cuycle and tehn start its preheat cycle, sitting around until it beeps to tell you it's time to add beans, but that can take ten minutes or more. There are ways to speed the process up. As soon as the machine stops after a roast and cool-down, pull up the rear filter (or remove it from the machine) and remove the bean-fill lid. Use great care- some of these parts will be exceedingly hot and can burn instantly. Now just begin a roast again. The machine will automatically go into cool-down mode until the internal temperature drops to its pre-determined level.
2) How should I clean the machine out?
The included manual covers most of the cleaning procedures that you should do on a regular basis. But there are other things that can be done as well (although they can void the warranty so are not included).
Once or twice a year it is a good idea to remove the rear cover to clean out all the stray chaff and bean bits that can gather in there:
1) Unplug machine
2) Remove loose parts (bean fill lid, grillwork, cooling tray, etc.)
3) Pull out the rear filter.
4) Remove the screws holding the fan housing to the rear of the machine. Make mental note of how firmly (or gently) the screws are torqued into place.
5) Pull fan away from machine and unplug the fan's cable (it is polarized) and place the fan assembly aside. If you feel some need to remove the fan from the mounting piece, be sure to use some liquid paper to mark its orientation. It needs to go back in facing the same way.
6) Now remove the remaining screws that hold the plastic rear cover of the machine on (there are two hidden beneath where the fan mounts).
7) With the rear of the machine removed it is an easy matter to use compressed air to clean out the machine. Use care not to displace the material in the top filter.
8) Reassembly is the reverse of the above. Place the back on and start all the screws before tightening any of them. Be VERY careful to only tighten the screws until just past 'seated.' They DO NOT have to be very tight and can be easily stripped!
3 I just can't manage to get my beans dark enough no matter what I do.
The first thing to check is the line voltage when roasting. Newer models are voltage compensated and the heating elements are made to close specifications. Anything over about 115v will work for most folks, best results can be had at 120v or more. Below 112v and roasting a 250 gram load to a dark roast may be difficult. Solutions include:
1) Roasting smaller batches. Try 200 to 225 grams. Use caution. The smaller the batch teh greater rsk of burning the beans or creating a fire hazard.
2 Try using the machine at a different outlet where the voltage is sufficient. If it works better there, then what you might need is a "Variac." This is a variable transformer that can supply more then the line voltage is capable of doing on its own. These cost about $115.
4) How do I clean the black air filter material?
The filter material can be washed. The easiest (and safest) way is to remove the material from its carrier. The holder is two pieces which snap together. CAREFULLY remove the black material and place it flat on the bottom of the kitchen sink. Soak it with a GENTLE water spray from the faucet and then use some soap. Let it soak, then rinse thoroughly. Carefully place it flat on a towel, and press out the water with a sandwich of towel. Place it back into the holder. USE CAUTION as the black material is quite fragile.
Also, be sure to check my lesson and review/test on how to install a Permanent Filter Replacement for Hottop, and also note that there is a piece of this black filter material in the top vent. See What is that vent thing on the very top of the machine?
5) My Roasting drum is a mess from burnt coffee oils and stuff. How do I clean it?
Remove the drum from the machine (instructions are in the manual) and soak it in a strong solution of espresso machine cleaner, TSP, or similar. After soaking for a few hours you might want to re-heat the solution and soak the drum some more. After a while try scrubbing with a stainless steel scrubber, stainless steel bristle parts cleaning bruch, or similar tool. The drum is stainless steel and can take it! On early models with a single support in the drum it is easy to displace the shaft while shoving your hand in there to clean the drum, after assembling the machine be sure to check the drum alignment What can I do if I find that my drum is out of alignment?). Use a long handle brush and take care when placing your hand in the drum to avoid abrasions and lacerations.
6) There have been times when a brown-colored liquid drips out of the back end of the machine. What was that?
Once in a while the machine has biological needs like anyone else... Actually, coffee beans contain a lot of moisture. When roasted this moisture is released from the beans and can condense in the machine and will drip out the back of the device. This will be more noticeable in humid climates and/or in colder weather. I don't think it is anything to worry about. If your coffee was properly prepared by the grower/processor there isn't enough moisture in the beans to cause concern. If you are worried about it, go to How should I clean the machine out? and open the back and take a look.
7) Does it really get as hot as some people say?
Yes, it really does. A brief brush across the exposed outer-surfaces of the roaster, particularly near the front two-thirds can get you a decent first degree burn. Anything more than that is just about guaranteed to supply you with a second degree burn.
8) Is it sensitive to voltage?
Old models were somewhat sensitive to low-voltage situations, but the newer models are voltage compensated and are not so sensitive. If your line voltage when the heating element is on stays at or above around 115 then it should be fine. See I just can't manage to get my beans dark enough no matter what I do for ways to deal with problems that might be voltage related.
9) What is the actual capacity of the roaster?
It depends on your line voltage as well as the heating element (in earlier versions, particularly). If you have a newer model as well as good line voltage (in the 115+ range with the heating element on), then it can be possible to roast as much as 300 grams (although for best taste it is recommended tomstay around 250 grams). If you do light roasts for drip or such, then 325 or as much as 350 grams may be possible although the roasts are not quite as even or developed. Generally, I would recommend no more than about 250-300 grams.
10) What is that round thing on the back wall of the roast chamber?
That is a temperature sensor which is used to display the temperature on the control panel as well as to give data to the safety systems. Another function of the sensor is to read the chamber's temperature at the beginning of the roast and then decide whether it needs to cool down first or begin the roast.
11) I keep getting one or two burnt beans in almost every batch. What's that about?
There are a few spots in the drum where beans can possibly get caught. The most likely are under the "wound" wire ejector and between the edge of the agitation fins and any other part they are near (like the ejection coil or the support triad). The best thing you can do is to remove the front before each roast and remove any stuck beans. If a properly-roasted bean gets left in there they will be quite burnt during teh nest roast cycle (near-completely carbonized) and the burnt taste can taint the roast.
I made a tool out of a length of brass brazing rod stuck into an old screwdriver handle. It makes quick work of "poking" out any stuck beans without having to remove the drum. Any similar tool like a thin shish kabkb skewer, thin wood dowl or a chopstick will work as well. Be sure to check all areas of of the drum- if done gently, the drum can be rotated by hand, apparently without any ill effect to the roaster.
12) Is there any way to use this roaster indoors?
The Hottop roaster, like virtually any device made to roast coffee, is going to create smoke. The more coffee you roast at one time, the darker you roast your coffee, the more smoke you will create. Roasting a half pound to a dark roast (like into second crack as most folks who roast espresso do) will create enough smoke to get you into trouble unless you live alone and without smoke detectors. Roasting really dark, like oil showing, will produce enough smoke that it might get hard to breathe in the kitchen! And seriously, the smoke is an allergen, and even if you are not allergic to it now, it can become a health problem for you in the future- you don't want to be breathing this stuff!
My first suggestions would be to consider this device as if it were a BBQ and to roast outdoors. After that, if you have an efficient range hood that actually is exhausted to the out of doors and can get the roaster safely up high enough then maybe you can use that. A downdraft exhaust will not work properly. Be aware that some of the "modern" hoods are just air filters and have no ducting to send the smoke out of the structure.
You might try a box fan mounted in a window with some sort of hood made of wood, Plexiglas, or metal. Be aware that the hood will be subjected to the heat of the roaster, so do not create a fire hazard! The large ("19"?) fans move a lot of air. I use one (without a hood) in the window of my garage and roast on the workbench. Be aware that depending on how it is arranged, it can pull heat out of the roaster and lengthen the time it takes to reach your desired roast level.
13) Every now and then the drum just stops and I have to quickly shut down the machine. What is that about?
I will take for granted that the roaster is still powered up. It might be caused by one of the following:
1) If it always happens about the same amount of time into the roast, then it could be a motor problem. The motor seems to be a heavy-duty item, and not prone to problems, but it could be that it overheats after running for a given amount of time.
2) An out-of-spec drum- at least to say, the problem is that the total, outside length of the drum is smaller than the inside length of the roasting chamber and it allows enough space that beans get caught between the drum and either the front or the rear of the chamber.
3) Less likely, but it is possible that the front bearing is too "loose"- that is, it needs to be bent backwards to place more pressure against the drum so that its pushes towards the back of the roasting chamber with greater force. If readjusted, it would make it more difficult for a bean to get caught back there.
4) The drum's length is either "out of round" (irregular) or the two ends of the drum are not parallel and so there are areas between the drum and the chamber that allow beans to fall through.
5) Small stones can get caught between the end of the drum and the chamber. Many time you can hear this, but also see the effects as the stone will often cut a small grove (radial scratch) in the machine- either in the chamber wall, front cover, or the drum.
6) An electrical fault such as noise on the line, low voltage, or a wiring problem internally.
7) Something else.
Number 2 through 5 would be exacerbated by roasts that contain smaller beans (or small stones). Try some roasts with larger beans and that are free from stones to see if it makes a difference. Also try running two or three consecutive roasts without beans to see if you can make it happen when there is nothing to jam the drum in the chamber.
14) What can I do if I find that my drum is out of alignment? (This applies to early model drums with only a front-support vane. Later moidels have the drum supported at both ends.)
Take a look at this representation of how the the drum is supported on its shaft:
The blue lines represent a properly aligned drum. The back end of the drum on the right (furthest from the window) isn't supported by anything. The drum is only mounted to the shaft at the window end (the vertical blue line in the drum above are the "spokes" you see going by through the window during a roast). During shipping (or at any other time between manufacturing and now), if the machine was dropped or mis-handled, those front supports that hold the drum to the shaft be can bent causing the drum to be out of alignment to its shaft, and thus, not be parallel to the roasting chamber. The red rectangle represents the drum out of alignment. You can see how it changes its overall length in relation to the roasting chamber (green).
[NOTE- later models of the Hottop came with supports at both ends of the drum, so this mis-alignment problem will not likely be a problem any longer]
You can check for this [*1]: In normal operation, the top edge of the INSIDE of the roasting chamber is roughly even with the top edge of the load chute. We can use this fact to our benefit:
1) Remove the front cover and the load chute cover.
2) Stick your finger through the load chute and up into the chamber.
3) SLOWLY and CAREFULLY rotate the front of the drum by hand, and feel the motion and alignment of the drum through the chute opening. It will be easy to feel if it's out of true as it will feel like it is going up and down in relation to the position of your finger.
4) If you find it out of alignment, turn it until you feel the lowest part go by, and stop it there.
5) Carefully support the front of the drum with one hand and push up on the inside of the rear of the drum with the measuring finger. With a bit of trial and error you can get it to run true this way, and it will stay that way unless the unit's dropped again. f you cannot, you may need to remove the drum and align it outside of the roaster. A set of machinist's "V" blocks and a dial indicator can be useful for that.
5) After doing this adjustment you might find it only takes a small amount of effort on the Gold Screw to align the bearing. If that is the case, you might need to adjust the bearing. See My drum makes noise no matter how I adjust the Gold Screw for that procedure.
*1- CAUTION- It is possible that this test exposes you to sharp edges, and if you aren't very bright, to the insides of a hot roaster. I recommend doing this with a COLD machine, and wearing some gloves to protect your skin. Also be sure to unplug the machine before starting.
NOTE: Newer machines have a redesigned drum with the same supports in the front as well as an added support in the rear of the drum. Alignment issues should no longer be a problem.
15) My drum makes noise no matter how I adjust the Gold Screw.
The first thing to do is to check the interface between the front bearing and the tip of the drum's shaft. Be sure that both surfaces are clean and smooth. Sometimes a little lubricant works wonders for this interface. One user stated that Radio Shack sells food-grade grease that works for this (Part number 64-2326 "Multi-purpose Lube Gel" Works in -45 degrees to +450F).
If that isn't the culprit, in some cases, for various reasons, the front bearing will not be placing enough rearward pressure on the drum shaft and no matter how you seem to adjust it, the roaster keeps making rubbing or grinding noises- both bad.
The Gold Screw, when tightened, pulls the bearing plate forward, towards the glass window, and relieves pressure on the drum's shaft. To increase the base amount of pressure the bearing exerts on the drum:
1) Remove the drum from the roaster. While the drum is out, check the edges of the drum for deformations, burnt-on crud, stuck beans, rocks, or anything indicating that it is rubbing. Do the same inspection on the rear wall of the roast chamber.
2) With the drum removed, reinstall the bearing plate and seat the four screws.
3) Place a straight-edge across the front of the roaster and measure how much space there is between the straight edge and the tip of the bearing. You might have to come up with a way to accruately mark its present location.
4) Now CAREFULLY and GENTLY press the "tongue" of the bearing plate into the roast chamber. You are trying to bend it SLIGHTLY, with the fulcrum and bend-point being the radius of the inside edge of the roast chamber.
5) Repeat step 3. A total of about 1/16" (an no more than 1/8") additional clearance, at rest, with the bearing further into the roast chamber, measured at the tip of the bearing plate should be sufficient. You can always repeat this at a later time if you feel the need.
6) Reinstall the drum and the front of the roaster. At the beginning of the next roast, loosen the Gold Screw. You should hear the drum rubbing. Seat the Gold Screw, then Slowly tighten it. About a turn or two at the most should be sufficient to make the noise stop- probably less than that should be necessary.
16) My Hottop seems to be making a grinding noise when it is running. What could that be?
There are a few places that the grinding noise is most likely coming from:
1) It is possible that the front bearing needs a bit of lubrication or is improperly aligned. To test this, if it is the front bearing making the noise, then tightening the gold knob a bit more will make decrease in amplitude. Remove the front of the machine then remove the screws holding the bearing plate in place. Remove the plate and examine the dimple where the drum's shaft is seated s well as the end of the drum's shaft where it rubs on the dimple. If that all looks OK, then it could be that it just needs a bit of lubrication. To test this try a droplet of vegetable oil in the dimple. If that works, then you will need to get some food grade silicone lubricant.
2) The drum is rubbing on the front of the machine. If that's where the noise is coming from then loosening the gold knob a lot when it is running should make it lessen. Examine the inside surface of the bearing plate (the interface between the end of the drum and the plate). If there are signs of rubbing or gouging the bearing may need adjusting so that it places a bit more rearward pressure on the drum.
3) The drum's shaft locating pin is bent. If the drive pin that goes through the far end of the drum's shaft is bent it may not allow the drum to seat properly in the drive connection. Be sure that the drum can go completely into the shaft. .
4) The drum is rubbing on the rear wall of the roast chamber because it is out of alignment. This more a problem with earlier models. Among other causes, this can occur from rough handling during shipping. It is covered at What can I do if I find that my drum is out of alignment?
5) It is possible for a rock or a bit of bean to get caught between the drum and bearing plate and/or back wall of the roast chamber. This can push the drum in the opposite direction (debris at the rear pushes the drum forward and causes noise at the front). Remove the drum and check.
6) The drum is not seated properly. There should have been a note included in the instructions or shipping box stating that you should be check that the drum is properly seated in the bearing before operation. Shipping or rough handling can cause it to unseat. Check that the drum did not pop out of the front bearing before starting the machine.
17) My roaster's filter is about dead, and new ones are $8 each plus shipping. What would you do?
At $8 each the filters can get expensive. Evidently, the new white, paper(?) filters are not washable, so the expense can accumulate quickly, particularly if you are roasting a pound or two a week.
Be aware that I have not personally tried this yet, but my first attempt to remedy the situation would be to look for a similar material that is used in a furnace filter. The problem is that these are normally input filters and not intended to take the heat that the Hottop produces. Some experimenting is in order to be sure that they would not ignite or meltdown in use. If you do find a particular filter material that works and is readily available, please share it with me (brand and model/type). One medium size furnace filter which sells for about $4 to $8 could make at least a dozen or more replacements for the Hottop's rear filter. The loose fiber filters (Fiberglas, etc.) are not suitable.
Choosing a material that works in cooperation with the roaster's design is important. The Hottop depends on some predetermined range of resistance to airflow through the rear filter. Too much resistance to the air flow and the roasting chamber will overheat and cause an automatic end to the roast cycle (and a smoky flavor to the beans). Too little resistance to the air flow and there will be insufficient heat to finish the roast properly. Based on that, If you couldn't find the proper fibrous material I would look for some metal screening or perforated metal to use in place of the filter. I always roast out of doors so I don't care about the smoke. The metal could be bent in a serpentine shape so that it would stay in place in the filter holder as well as increase the total surface area.
I remind you again that these are theories and not tested by me or anyone else that I have yet heard from.
18) What's a good cleaner to remove the burnt accumulations off of things like the drum, viewing window, and other areas?
Generally speaking, a build up off residues in a roaster is a good thing. A new coffee roaster needs to be seasoned before it can create its best results. But it can get to a point that the crud gets so heavy that it retains and transfers a burnt smell to the coffee, or with the perforated drum, interferes with the transfer of heat or ejection of chaff and bean particles. In that case try "Cafiza" from Urnex. This is a new espresso machine cleaner from them, and it works great, easily removing the brown layers after a short soak. TSP also works quite well.
19) What is that vent thing on the very top of the machine over the roasting chamber and how do I clean it?
On top of the machine, in front of the bean loading chute, is a vent. This vent has a piece of the same filter material as the rear filter (the black, delicate, carbon fabric). Care must be taken when using compressed air to clean the roaster as this fabric can be damaged. To remove the material for cleaning, the easiest way is to use a small hooked tool (like a small crochet hook or bicycle spoke) and hook just the grill portion in the top vent and pull it out. Work around the grill, pulling at the corners in succession- do not try to pull it out from one spot. The outer rim of the filter (the solid part with the two screws in it) will stay in the machine. Wash the material as is stated in 6) How do I clean the black air filter material?
20) Besides the normal cleaning like emptying the chaff tray and cleaning the glass window is there any further cleaning I should be doing with my Hottop?
Yes. Although some of the following may void the warranty, there are some other cleaning tasks I feel you should do.
About every month or so you should remove the chaff tray, bean loading cover, rear filter, top filter, and cooling tray and using compressed air blow the machine out as well as is possible. Chaff collects all over and it makes quite a mess.
About every two or three months inspect the rear wall of the roaster. If the temperature sensor is getting more brown then silver, remove the drum and clean the back wall with some espresso machine cleaner. Use care not to drip water into the electronics.
About once or twice a year I suggest removing the rear fan and rear cover of the machine along with the drum and all other removable parts including the top filter and give the machine a thorough cleaning. This would entail using compressed air (like at the gas station and not one of the canned air products) to blow out every nook and cranny you can find. Then give the roasting chamber a good cleaning with some strong espresso machine cleaner (I used a Scotchbrite pad as well). Use the same cleaner to clean the drum and other parts that have burnt-on coffee residue. The rear fan will also have a good coating of coffee dust so be sure to clean that as well.
- When using compressed air refrain from blowing the fans and causing them to spin at high speed. This can damage their bearings and cause them to fail prematurely. Use a tool of some sort (like a toothpick) to keep the blade from turning when blowing the fans off.
-When cleaning the roasting chamber use the cleaning solutions sparingly so as not to drip water into the electronics.
- Do all the cleaning tasks with the unit UNPLUGGED, and do not plug it in until it is completely assembled.
- Be sure the drum turns freely and the machine is completely dry before starting the machine.
21) How often should I check for Chaff and other crud and how do I get it out?
It is best to check the roasting chamber for stray chaff before every session when the machine is still cold.
One reader reports that after doing a half dozen roast on a new machine he removed the drum and found that about two tablespoons worth of chaff was accumulated between the drum and the right side wall in the back of the roasting chamber. This was after dutifully emptying the chaff tray after every roast and even using a chopstick to retrieve chaff that lay in the tray channel with the tray removed.
To make this easier, he got a Black and Decker hand-held vacuum and fashioned an extension tube for it so that it could reach all the way to the back of the chamber through the chaff tray opening. [You can make the extension with some vinyl tubing or even a length of thin wall copper tubing. Always unplug the machine when cleaning.] Using it after every roast (and after the machine cools down) he always get chaff, sometimes a considerable amount, none of which would likely ever show up in the tray. The vacuum also comes in handy for the rest of the post-roast clean-up.
22) How much of the machine should I take apart for cleaning?
For a thorough cleaning remove the following:
-All 'loose' parts
rear filter (#13)
chaff tray (#9)
bean loading door (#4)
cooling tray (#7)
heat protection grills if so equipped
-front cover (#10)
-bearing plate (#11)
-You may also wish to remove the top filter once a year or so.
Do not remove the front nose piece to which the bearing plate (#11) is attached. A reader reported that he removed and that it was very difficult to get the screws back in place (still not replaced after one hour of efforts).
23) I installed a thermometer like you did in the Chaff tray. Why does the temperature go up really fast near the end of the roast?
If you are roasting large batches (275-310 grams or so, green weight) the roast will produce a lot of chaff. Some can be transported to the heating element, and then dropped into the chaff tray causing the chaff to catch fire. I have seen the same sudden rise in temperature, going into the 600-700 degree range. What you are actually seeing is the loose chaff in the chaff tray igniting and the high temperatures are from the combustion of the chaff. This is yet another reason that a coffee roasting appliance should never be left unattended.
I stopped using the chaff tray thermometer, instead I have installed a thermocouple through teh loading door on top of the roaster. Check my Add Bean Temperature Monitoring to the Hottop article to learn how.
24) Is there any way to get the original filters to last longer?
One user reports that he found that the filter seems to get dirty in one quadrant- an effect of the air flow through the rear of the machine and the way the fan works presumably. He found that he could extend each filter's life by removing it from the holder and rotating the filter 90 degrees in the holder- spinning it ¼ turn at a time.
25) The fan at the back of the machine needs replacing. Are they availble?
The fan itself is a 120mm, brushless DC computer-style fan, but it is best to get one with the same specs. That is not quite as important with the "B" model since the fan speed can be user-controlled.
26) What can I do if it goes into cooling cycle right away, or the beans eject WAY too early?
If this is intermittant and happens for no apparent reason, check for a loose connection on the back of the temperature sensor (see the Temperature Sensor page in the repair section at the HopttopUSA website for instructions on how to get to this part).
27) My Hottop seems to be making a lot more smoke out of the top vent now. What causes that?
If your Hottop seems to be making a lot more smoke than before here are a few things to check:
1) There is a filter under the perforated stainless steel cover on top of the machine. You can remove the stainless steel perforated part ( see What is that vent thing on the very top of the machine over the roasting chamber and how do I clean it?.). Held between the two parts is a piece of black fabric filter material. This has a life span and it can also be displaced if compressed air is used to clean the machine. You can cut a new one from an old rear filter or order a replacement from Hottop USA.
2) Have you changed the rear filter lately? If the rear filter gets clogged with particles the smoke will fill the machine and look for another exit as it builds up.
3) Is the rear fan working? If this fan fails the same result will take place- smoke comes out in lots of places. These are 120mm computer fans so replacing them is easy- instructions are on the Hottop USA website.
4) Clean out the roasting chamber. If you let excess chaff and build up inside the roasting chamber it can cause excessive smoke as it burns off as well as creating a fire hazard. To a lesser extent the same can said for the coffee oils that build up.
28) My Hottop is ejecting the beans right at the beginning of the roast. Do I need to send it back?
If you are talking about a machine that goes into the cooling cycle real early in the roast or even before the beans are added there can be a number of causes.
One cause is high voltage. There have been some cases where folks have used a device called a Variac to up the voltage going into the Hottop. A Variac is a variable transformer that can lower or raise voltage through a user-adjustable range. This can be a good thing if the voltage in your home is less than around 115VAC. These often have a voltmeter on them that reports the output voltage. Unfortunately, some of the units have a meter that does not make it easy to see the exact voltage or are inaccurate. If you are using a Variac be sure to use a dependable voltmeter to check the accuracy of the device so as not to end sending a too-high voltage to the roaster. High voltage can cause the heating element to develop heat faster than the unit has been designed to handle and can cause the beans to eject early because the safety systems designed into the roaster think that the fast rise in temperature could be a fire and will automatically stop the roast. Too high voltages also have the potential to cause a hazardous situation or may damage the Hottop by overheating the heating element and causing it to warp or damaging electronic components not designed to handle such high voltages.
Another cause of early ejection can be failure of the control panel. If you rule out a voltage problem with an accurate voltmeter replacement of the control panel is a likely solution. It also happens to be one of the very easiest parts to change as well!
Finally, and more rare, are the push-on connectors on the back of the temperature sensor. If the machine has been working fine for some time and if nothing else has changed and the beans begin ejecting early, this could be the cause. They appear to be made of aluminum and can become loose over time. If the signal through the sensor is not picked up by the control chip, the programming sees this as a dangerous fault and ejects the beans. You can check the repair procedures at the HopttopUSA website and see how to access the connectors if you are having early ejection problems.