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Panel Display Failure
NoTan2
Hi,

My first post here. This seems to be a most interesting forum - I only discovered it after some searching on Hottop display problems.

My normally reliable "B" developed a problem a couple of months ago. The LCD is only showing the backlight. The roaster still seems to start up and eject (pressing buttons from memory). I bought it new and it's quite a few years old - it doesn't have the manual eject.

I've been roasting with the heat gun and bowl since it failed and that's a bit hit and miss so I need to make time to debug it and resolve the issue.

Another poster reported the same symptoms here back in 2012 but didn't receive any replies so perhaps it isn't a common problem?

Replacement panels aren't exactly cheap here in Australia, otherwise I'd just buy one and be done with it (hopefully). I've got it stripped down so I'll go over all the contacts with Deoxit and then do some diagnostics with my DSO and DMM in case it turns out to be the main board instead of the panel.

Does anyone have any experience with this fault and perhaps the cause?

Thanks,
Paul.
 
ginny
Hi Paul:

you really popped into te right place for this...

one of our members is the Guru of Hot Top Mr. Randy G and he will solve this or you; I have an idea what it is but let's wait and see what Randy has to say that way I will not lead you down the wrong path.

I will drop Randy a note so he knows you are here with this problem!


ginny
 
NoTan2
Hi ginny,

Thank you for the quick response. I had noted that Randy G was a frequent poster here. I used to follow his activity on other forums way back when we all had Rancilio Silvias.
 
Randy G
I am not an electronics guy, but this is most likely a problem with the video driver chip on the control panel. That really doesn't matter because unless you are an electronics engineer you can't likely fix it anyway (I never have even thought about fixing such a problem. So the only reasonable solution is to replace the control panel.

But the KN-8828B and the later direct replacement panel, the KN-8828B-2 panel are no longer available, what are the alternatives? There are the current options:

? The "B-K kit." This includes a KN-8828B-2K control panel, a K-style thermocouple, and a new roast chamber rear wall.Note that unless your machine already has the emergency eject knob on the back cover under the fan, this kit DOES NOT add the "-2" functionality. It only converts the machine to a "B-2 even though the panel is marked "KN-8828B-2K." This kit requires removal of many of the internal components for installation. We have full, step by step instructions for this procedure HERE

? If you do not have the emergency eject knob on the back of the roaster and that is something you would like to add, the "B-2K Kit" includes all the parts to update to that functionality. It includes the B-K kit parts as well as a new eject mechanism, horizontal frame member, rear cover, new motor mount, and related parts for installation. The installation of this kit requires near total disassembly of the roaster. We have full, step by step instructions for that HERE.

? The KN-8828P-2 control panel which would just be a panel change. While that is a viable choice and the easiest to install, it is only a little less costly than the "B-K" kit and you would lose the manual control offered by the "B" control panel.

? The KN-8828B-K+ upgrade kit would give the function of our newest model. It is also available with the manual eject upgrade to make your roaster a KN-8828B-2K+.

Our "Upgrade Center" has the details on the above information and what is necessary to upgrade any model of our roasters to any other model. There are links to all the kits and other parts to change models, and the the links Instructions for installing the upgrades as well.
If you have any question or need further assistance, please do not hesitate to contact us.

Look those over as well as the information in the Upgrade Center, and if you have any questions concerning functionality or the procedure to install any of those kits, please feel free to contact me at [email protected] I do not wish to do business here.

Life's too short to drink bad coffee.
 
NoTan2
Thanks for the detailed response, Randy.

We used to have a good distributor here in Australia. It has changed hands recently so hopefully they will continue the good service. I can buy the parts from them.

Since there's nothing to lose, I'll have a look at fixing the panel (as long as it's a through-hole board and not SMT). Failing that the "B-K" kit is available here.

I've stripped the roaster down a couple of times before. The outstanding level of detail and pictures on your support website makes maintenance very straightforward.

Once again, thanks for your assistance.
 
Randy G
I had no idea that the Australian distributor had changed hands.

I know it is expensive, the the control panel of the "+" kit is a total redesign and the rotary controls which replaced the switches are a great improvement (although I almost never touch them preferring to control the roaster using Artisan).

Thanks for the kind words about my work on the website, and I really have made it a personal goal to give the best customer service I can at Hottop.

Life's too short to drink bad coffee.
 
NoTan2
Since I was changing the panel and thermocouple, I decided the machine was well overdue for a good clean.

After stripping the roaster down, I found that the heating element was bent out of shape. This explained the scraping noise it had been making for a few weeks before the panel failed. I can see the scratch marks on the drum.

Curiously, the scraping noise stopped after the roaster started to warm up, so perhaps the element changed shape as it heated up.

So, the final parts list is a new panel, K-type thermocouple, front cover and glass, heating element and fusible link. Together with a new Top filter and a few rear filters, they all arrived on Monday.

Following Randy's excellent instructions, a good soaking in the closest Australian equivalent to OxyClean made everything look new again.

We're all good to go for a reassemble on the weekend. (Hopefully I can pack the heat gun and bowl away.)

One question...
The instructions for installing the new heating element suggest that it should be cleaned with a suitable cleaning agent first. Since, I've never cleaned a heating element before, can someone suggest what might be a suitable cleaning agent?

Thanks,
 
Randy G
NoTan2 -
Thanks for the kind words. It does this old teacher good to hear them, I assure you. I love applying my teaching skills to my mechanical abilities and repair sense, and sharing it with others... Sort of the definition of teaching, no? Making a meager living at it is the cake's icing.

Maybe some alcohol or other residue-free household cleaner for the element. Maybe even Windex or the equivalent. Don't soak it. Just dampen(!) a rag and give it a wipe and drying wipe. We just figure that thee might be some manufacturing "residue" on it. Never been a problem, but since it is in close proximity to a food product we would rather have that off of there, just in case. It is also why we advocate an "empty roast" first (no beans).

Life's too short to drink bad coffee.
 
turtle

Quote

Randy G wrote:

Thanks for the kind words about my work on the website, and I really have made it a personal goal to give the best customer service I can at Hottop.



I find that the Hottop web site and the Baratza web site are the most customer friendly as far as parts, upgrade kits, diagrams, and instructions go.

After fighting with Mazzer for weeks to NOT get parts, finding companies with good customer service employees like Hottop and Baratza have who are friendly, knowledgeable, AND willing to help their customers is breath of fresh air.

Thank you Randy. Both for your efforts making the Hottop site so informative and helpful as well as giving your time to help on all of the coffee web forms which is way outside of your "job description"

THANKS!!!
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: 2 kilo Chinese drum
Grinders: Mazzer Major - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
 
NoTan2
Thanks Randy,

I have some isopropyl alcohol. So we'll go with that.

I'll second what turtle has said. Your website takes me back to when I bought a Z80/S-100 business computer in the late 70's. It came with 100's of pages of technical manuals, schematics, troubleshooting etc. I wrote a (real) letter to the manufacturer in California - no internet then - and received a detailed response.

That attention to customer support seemed to persist through to the late 1980's and then mostly fizzled out.

Good to see that Hottop is still hanging in there.
 
NoTan2
First problem...

The new Fusible Link did not come with a new bracket or screw.
The instructions say not to reuse the old bracket.

It's going to take weeks to get a new bracket from the supplier. I assume that the new bracket is a different shape from the old? Can I modify the old bracket to fit the new Fusible Link? Perhaps the diameter of the new link is larger?
 
Randy G
I have never compared the brackets. SO long as the bracket 1) holds the center part of the link to the chamber wall, and 2) does not crush the link, a handy person should be able to adapt the old link.

I assume you did not get it from Hottop USA. Ours come packaged with the bracket (at least they always did before)..

Life's too short to drink bad coffee.
 
NoTan2
The old link is somewhat thinner in diameter than the new one, Randy. The old bracket won't fit. (and it's not big enough to adapt)

Not going to let it stop me - I'm heading off to the hardware store to see if I can find some suitable stainless stock to make a new one. I've made plenty of brackets for model aircraft and other things over the years.

No, I bought it from the Australian distributor. The picture on their website shows a bracket and screw so it must have been left out for some reason. I've emailed them.

I've always assumed that Hottop USA doesn't sell directly to us aussies. We're 240V so anything electrical (at least non-DC) wouldn't work anyway. (But it is nice to have plenty of volts available for roasting.) Grin
 
NoTan2
Finally got it all back together.

Triple checked the wiring. Made sure that the eject solenoid was moving freely and the spring was holding the door closed. (I had to replace the eject mechanism a few years ago).

Fired it up with no beans. Panel came up, I set it to AD1 and let it rip. All looked fine - the motor started up, the new 'K' type thermocouple was reading a reasonable temperature. Left it in preheat for a minute or so to make sure the heater was working and the thermocouple was responding and hit Eject.

Didn't hear the eject operating so I unplugged it and removed the front cover. The eject door was closed and wouldn't move.

Removed the fan and back cover and the eject solenoid was jammed. Managed to get my finger in and freed it up and worked it a few times and all looked OK. Couldn't understand why it had jammed so decided to try it with the back cover off and see what was happening. Plugged in the rear fan temporarily and powered it up.

It immediately tripped my RCD. Got the torch and quadruple checked the wiring. Tried again and tripped the RCD again. Unplugged it and just walked away.

I probably shouldn't be posting so soon after the event but after spending over $500 on parts and weeks of work stripping, cleaning and carefully reassembling, I'm feeling pretty negative about the roaster.

If the main board is fried, it's almost $400 for a replacement. It's just not worth it.
 
Randy G
Disconnect the electrical connections that connect to the spade terminals on the main board. Those are all the components that operate on mains current. make sure they are isolated and cannot cause a short.

1 - Start the roaster and see if it works and does not trip the breaker.
2 - Disconnect from mains and connect just the eject solenoid. See if the breaker trips.
3 - Disconnect from the mains
4 - Disconnect the solenoid
5 - Repeat test starting at step 2 with another component.

I can only guess at the cause, but this will help figure it out faster and more accurately than my guessing.

Life's too short to drink bad coffee.
 
NoTan2
Once again, Randy, thanks for the quick response.

With all the spade connectors disconnected (except the Fusible link resistor), the panel lights up, goes "beep" and enables the green power button. I can select (for example) Ad1 and then adjust the max Time and Temperature defaults.

So that suggests that the main board and my new Control Panel are OK. That's a relief.

I don't have any more time today, unfortunately. But I'll continue the fault finding later.

I wasn't sure if it was OK to power up the roaster with the various components disconnected so thanks for that advice.

Thanks again, Randy.
 
Randy G
No problem. I think we have all "been there," immersed in frustration.
I am in a somewhat enviable place- to have first become a home-roasting enthusiast, then an independent proponent of the Hottop, and now working for them.

Let me know how it goes, and if you have further problems please e-mail me at Hottop USA.

Life's too short to drink bad coffee.
 
NoTan2
Finally found the time to get some traction on this.

All worked fine with everything plugged in minus the eject solenoid. So I decided that there was nothing to lose by taking a good look at the solenoid.

It didn't smell like a "fried" relay but the resistance readings at the terminals were a bit strange so I cut off the large flat piece of heat shrink and found, not surprisingly, a bridge rectifier (KBP04) and flyback diode (1N400? - couldn't read the last digit.)

After disconnecting the relay from this, the windings resistance showed as around 6K which was reasonable for a 240V relay. Certainly worth replacing the semiconductors anyway.

The local electronics store only had an RS206 which looks to be the same family as the original but with higher ratings and an 1N4007 ought to be plenty for the flyback diode.

Soldered and heatshrunk everything, checked everything with the multimeter, connected it back to the main board, stood well clear and flicked the switch. The display lit up and beeped at me. Phew!!

Decided I was on a roll so I let it run to pre-heat and then hit Eject and the door opened and then closed 30 seconds later when the timer ran down. Tried again with the same positive results.

I fitted the covers, buttoned it up and gave it a dry run for about 5 minutes after pre-heat finished, both thermocouples were reading in a reasonable manner, all looked normal so I hit Eject and the door opened.

So for an additional $3 in parts, I seem to be back in business.

After I clean all the garbage off the bench, I'll try a real roast.
 
NoTan2
Ignore all that - it just failed again.
 
turtle
It is starting to sound like the typical B model eject button control panel failure that has happened to everyone who has owned that model roaster.
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: 2 kilo Chinese drum
Grinders: Mazzer Major - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
 
NoTan2
Hi turtle,

It is a brand new control panel. That's what started the whole exercise. The display failed so I've replaced the panel, heating element, fusible link, thermocouple and a few other bits and pieces.

When I reassembled it, I suspect that the solenoid fouled on the new thermocouple's lead (which I hadn't routed carefully enough) and possibly overstressed/overheated either the solenoid or the rectifier/diode. Replacing the rectifier and diode seemed to fix it temporarily but perhaps the windings on the relay have some kind of intermittent fault.

I had to buy a new eject door and solenoid early in the roaster's life because the spring was faulty and wouldn't hold the door closed. There was nothing wrong with the original solenoid so it should still be lying around somewhere. I don't believe I would have thrown it out but I haven't seen it for a few years. If I can find it, I'll try that one.

If that fails then it's back to the drawing board. I'm a bit reluctant to buy a new solenoid and eject door in case the main board is faulty. My next step is to disconnect the solenoid again and run it through a few cycles with no beans to prove that the main board is fine (with no solenoid connected).
 
NoTan2
Unfortunately, the main board appears to be faulty. I disconnected the solenoid, started the cycle and hit Eject - no problems. Tried again and my RCD tripped as soon as I hit Eject.

Not sure where to go from here.
 
turtle
there are only 2 electronic boards in the HT. If one is new and you are having issues still then you either have a DOA/defective new replacement or your other board is at fault.

Do you have a HTC board in thew too?
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: 2 kilo Chinese drum
Grinders: Mazzer Major - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
 
NoTan2
No, I don't have an HTC board, turtle.

The (new) control panel is highly unlikely to cause the RCD to trip since all the 240V mains voltage circuitry is on the main board.

Forgive me if I think out loud on this.

It only trips the RCD when I hit the Eject button and only occasionally and, as noted previously, I've also managed to cause one RCD trip without the solenoid connected. So I can probably eliminate the solenoid as the root cause.

Everything else appears to be working correctly - drum motor, agitation motor, heating element, rear fan, display, new K-type thermocouple so the control panel looks fine.

My main RCD has, over the years, decided to trip for no apparent reason, usually in the winter and in the early hours. According to my electrician friends, faulty RCDs are not common but I guess it's possible.

My swimming pool has its own circuit and RCD so I plugged the roaster into that circuit and tried it again a couple of times and it worked fine. At least it won't take out all my PCs, routers, clocks if that RCD trips.Shock

So, I'm going to remove the main board and give it a thorough clean. I cleaned it when the roaster was stripped down but I can see that I could have done a better job. I presume that coffee oils are conductive and that would be a prime contender for trouble.

Then, since it works most of the time, I'll try a real roast plugged into the swimming pool circuit. If the eject fails, I can whip off the front cover and dump the beans manually (I always keep some gloves handy).

Apologies if I'm annoying people with my troubles. But I've received some excellent advice so far and perhaps it might help someone else.
 
JackH

Quote

NoTan2 wrote:

Apologies if I'm annoying people with my troubles. But I've received some excellent advice so far and perhaps it might help someone else.


Absolutely no problem! I agree that it will help others.

This RCD is the same as a GFI here. I believe they are required on all residential wiring in some countries. Is it possible that the RCD is too sensitive because of a fault with the device? I think when you eject, the solenoid may create a disturbance that trips the RCD.
Edited by JackH on 05/19/2016 5:38 AM
---Jack

KKTO Roaster.
 
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