Hottop 8828

[wadds1]

Hi to everyone
I have just got my hands on what appears to be a very old hottop, I think it’s the original with no digital display so I think it’s a 8828. Came with a big 240 tp 110 volt transformer. Fired it up and no heat, tracked the fault down to a simple bad connection to the element. Running thru the buttons it appeared that the rear fan would try to work on the cooling cycle but was damaged so I fitted a 120mm fan from a pc which has the bonus of a little variable speed knob so I can adjust it.
Anyway I chucked some beans in it today about 220gm and ran it for a while just to see what happened. The unit has been sitting in the corner of a Wharehouse for many years before I scored it.
Let it warmup till it beeped on setting 4 ( medium ) and dropped in the beans. Seemed to be slow to roast and unlike some pictures I have seen I could not see the element glowing. The rear fan did not run. I ran I for about 15 min with still no rear fan and the beans were on their way but nowhere near roasted.
I think this early machine runs only on time and not adjusting the element but I don’t know and it’s hard with no temperature indication.
Anyway I ditched the roast to see if the eject worked and when I did the rear fan fired up during to cooling cycle.
so
should the rear fan run and when?
how long should a roast take?
does turning up the temp setting just increase time or drive the element?
bean charge weight


I will bang some more beans thru the old girl tomorrow when I have a little more time but was worried about the fan, maybe it kicks in later in the roast. Will also try cranking up the temp.

Buy the way I am a coffee roaster and coffee machine repair tech as well so am use to my commercial Joper and have beans to burn literally.

If putting a new controller panel and board in the old girl will make it usable I will look into it.

Any knowledge much appreciated.

[Javaphile]

Here's the manual for the US KN-8828 and KN-8828D: https://coffeesnobs.com.au/forum/equ...-owners-manual

That should help answer some of your questions.


Java "Manuals 'R good" phile

[Brewster]

Hi wadds1.
I have an old B model sitting in the shed for spares. If you are reasonably close, you might be able to find some immediate use for it.
Cheers
Mal

[wadds1]

Thanks for the input. I checked the manual online before i fired it up for the first time just so i knew what was going on but there is little information about what happens just how to use the thing . I tried another roast today and ran it out to nearly twenty minutes with one time add on then the machine dumped a really not cooked load of beans!
I am positive it is not getting hot enough the roast progression is way slow. I noticed also the rear fan not cutting in till i dumped the beans. I then shut down the roaster and restarted and the fan worked so i think it must be temperature activated.
I think the heat may be escaping straight out the top. The top filter is just an empty stainless cavity with holes in the top. Im thinking there must be some kind of filter material supposed to be inside which would help retain the heat as i can see heat waves pouring out thru the top filter vent. I have ordered a new top and rear filter and will re try as soon as they get here. I did notice a glow to the element today but will have to check if im getting a true 110v out of the transformer as well.

Hey Mal why did you ditch the old b model did it crap out? Is it 240v or 110? I would certainly luv the control panel and board as i think that would give me some control and temperature readout at least. The original unit gives you nothing! Im in Tassie though but would be happy to ship it and sort you out some coin if it was worth doing.

First i will see if i can get it hot enough to roast and then go from there i suppose. I am in a phase of fixing and resurrecting things at the moment instead of chucking them out so hopefully i will get this old wreck running. I have brought home 7 different coffees for blending and a couple for single origin roasts so am looking forward to creating a new recipe.

cheers all
Tim

[Brewster]

Hi Tim
It's 240v, was used constantly for nine years, was starting to show it's age and finally, it was the control board that failed. The display panel was also on it's way out and I had already replaced the element. I had an electronics guy from work have a look at it for me. He is "old school" and tested every component on the board. He found a faulty power thingy but by then I had decided it was time to purchase a new one.
They are a great roaster.
Cheers
Mal

[wadds1]

Well i just was checking out the machine and this is what i worked out for temp control.
The element switches on flat out until warmup temp (whatever that is )
min 0-1 drop element on/off every 10 sec roughly ( on for 10 off for 10 )
min 1-4 element on
min 4-8 element on/off every 10 sec
min 8-13.40 element on
min 13.40-17 element on/off every 10 sec
min 17- 18.30 element on

Really after that who cares.

I would have thought that the machine would hit the roast harder first up and not started switching off at 4 min. Certainly seems a strange way to do it compared to traditional roasting methods on a larger machine . I am used to inputting more heat at the beginning ( after T/A ) usually up to around 6 min and then backing off all of the way thru to the end. But thats a cast iron drum. Not really sure on this thing. Still struggling to get enough heat into it. Im running out of time and the machine is dumping the beans barely done with only 150 gm in it.

I could buy a cheap pid controller with thermocouple and ssd for the element for 30 bucks to control the temp and fit another thermocouple for bean temp all for probably 50-60 bucks.

Any thoughts much appreciated before i hack this thing up!

[Dimal]

I could buy a cheap pid controller with thermocouple and ssd

Rather than go too cheap, would be better to grab a Ramp-Soak controller that would then allow you to develop real roast profiles that could be replicated when you identify good outcomes...

Mal.

This Auber unit is decent enough and allows for very flexible operation.

[wadds1]

Thanks Mal.

I am looking into controllers and will post how i go. I am thinking I will try a variable input to the element instead of switching it on and off to control it but not sure yet.
Thanks
Tim

[wadds1]

ok

So i got a 10000w scr controller for the element and a ktype thermocouple probe and display

I fitted the probe just above the corner of the eject chute right in the bean path sticking in about 10mm.

So straight up you cannot put 110v to the element thru an scr running off 240v. At 110volts the element glowed bright red and i did a drop at 120 degrees c. Totally toasted the roast the husks were bursting into flames and had to drop the lot in ten minutes. It was pretty spectacular. lots of burnt beans and smoke. Why 110v thru an scr is different to the 110v from the transformer i do not know.

So just did another with more beans (300gm this time v 250 last). only ran 70v to the element and dropped at 90 degrees c. Worked pretty bloody well.

here are my temps

time temp element voltage

drop 90 c 70v
t/a 30s 83 c "
1min 85
2 92
3 99.7
4 106.7
5 112
6 118
7 124
8 130
9 135
10 141
11 147
12 153 dropped element to 60v
13 158
14 163 dropped element to 50v
15 167
16 170
16.45 out 173

not a very pretty curve but gives me something to work on. At least i know i can drive the thing now and pretty good result on second roast.
will try dropping hotter then run at lower power until t/a then crank it up next time i think with maybee 75 volts and then a earlier cutback to get some shape in this profile.

Any experiences, thoughts or suggestions much appreciated or if you have some hottop profiles to share would be great.

[Ted2013]

Does anyone know if there is an electrical wiring diagram available for any of the HOTTOP roasters. Could be very useful especially to someone trying to resurrect an old sick one like the one Mal has. Would be a great project for someone with some electronic nous.

[Brewster]

Not sure about electrical diagrams, but lots of good info here: https://www.hottopusa.com/index.html
Cheers
Mal

[snowytec]

Wadds1,
Might make sense to take a few steps back.
The filter at the top of the machine needs to be replaced, they are supposed to have a hard to source black heatproof filter material inside, similar to the black stuff part of the back filter, you could adapt a top filter from the new Hottops.
Both top and back filters are also used in tailoring the roast environment, (they partially block air flow and the programs need them to control the roast in the modern Hottops).
Heard of guys partially blocking the top filter with high temperature baking silicon sheet, but never tried it, (will if they put the prices up further).
The element should glow red in subdued light, make sure its not touching the wall of the machine but parallel along its full length by say 2-4mm.
You can get new elements / Filters direct from Hottop in Taiwan, (good people).
You may have to adapt a bit.
Cheers,
Snowytec.

[wadds1]

Thanks Snowytec
i have already blocked the top filter with aluminium foil as it was obviously losing tons of heat that way. I have brand new top and rear filters just not fitted yet.
I have been pondering overnight and think it might look at a chaff extraction system to replace the loading chute setup with a fan and collector. A lot of chaff is generated and just sitting down in the tray seems not ideal.
Gunna break out the welder and make a stand for the machine today.
Still after some profiles if anybody has them or do people just run an auto roast?

[snowytec]

Change the top &back filter, (5 minutes,one thing out of the way).
The chaff tray has to be emptied after every roast, the new units sense if it has been removed and won't work properly until the chaff has been emptied.
Tons of profiles available home-barista and some on Hottop USA.
Every machine is different, calibrate your machine against first crack 196C, (mine reads 176C at FC) and adjust your curves accordingly to start with.
The auto function is not for roasting, you need to create a profile by adjusting manually against time, store it - find that profile in memory and tweak that profile next roast, store it again etc.
You will end up with good stored profiles for your machine unless you have a fault.
(Remember, your model may work differently).
Cheers,
Snowytec.

[wadds1]

Here is my work for today. Switches for element controller and made a trolley setup for it. Just need to get a digital display for element readout but at the moment just using my fluke.
I think you misunderstand snowytec. This is a really old roaster that has nothing but run really. There are no standard controls or even a temperature read out so I have manualized it! Also is 110v and I’m running it 240v.
there are no profiles to store I’m graphing it out on paper so I can change it next roast by adjusting element voltage v time and bean temp all things that I have fitted to this bare bones roaster as well as a speed adjustable fan.
Havin fun now

[wadds1]

sorry for the bad pics i selected small size i take it actual is the go