Post By sitas
Unusual Sunbeam EM6910 problem? Machine getting very hot!
Well after an hour or so searching for this problem here and generally on google, I'm pretty stumped... What's happening is the machine is getting noticeably hot: too hot to be normal when touching the metal sides of it: Naturally the coffee is tasting burnt.
My thought is that there is some degradation of a physical connection (which maybe connects a metal side of the thermoblock to a thermistor). I don't mind getting my hands dirty: I had the thing open for an independent problem a couple of days ago; stealing the hot water switch to replace the steam knob switch.
So any suggestions? Has anyone had this problem before? I did find a lot of "too cold" posts or "machine never warms up all the way" posts, but nothing like this. On my next disassembly I'm going to make note of the resistances at appropriate points at room temperature.
Edit: I thought I should point out that everything else seems to be working fine: pressure from both pumps is fine, the thing heats up in its normal 2 minutes, water level sensor fine etc etc.
Sounds like the relay that switches the thermoblock on and off has stuck on. Someone else posted instructions (noidle22?) and part numbers I think for the 6910 but definitely for the 7000 (the instructions were so detailed I did one for someone else having never worked on a Sunbeam before). Desolder the old one and solder in the new one on the main circuit board.
Brilliant! I will give that a shot, see how it goes, and report back.
I had a similar situation with EM6910 being around 10 deg C hotter on the top cover (IR thermometer). I tried software temperature adjustment by 4*C which helped a bit but not enough for coffee to taste strange.
When the unit stopped switching itself off (remained on warm standby even when switched off by power button) I replaced the PCB board. bingo. Brew temperature back to normal.
Well I replaced both relays late on Friday night/sat morning.. No luck: I can hear them both switching and the two thermoblocks get boiling hot ++. No ready state though. Yep I think I'll try a new PCB if I can find one for a decent price... the 70 or 80 or so that they sell for through the regular channels seems a bit steep considering that my machine couldn't be worth more than AUD100 street value!
Thanks again CS for your help with background info on this machine. I have to say I was really impressed with the general construction quality inside: Really well put together machine.. if a bit cramped to work on! I wonder if it's due to Australian electrical appliance safety standards or, god forbid, sunbeam's high standards. Wonder why they went with such a cheesy metallic powder paint finish; imagine a matte-black cuboid looking thing, all right angles.
Off I go to PCB hunt.
Edit: Err.. hang on. The thing magically starts up fine when I retried it just a moment ago. Still way too Fing hot though!
Last edited by sitas; 19th November 2017 at 10:58 PM.
Must be. I'm arranging for a spare parts machine to swap out some components from!
Will report back with results if any : )
Sipping on V hot coffee until then.
These machines are not thermostatically controlled, both thermoblocks do have thermostats on them but they are for safety only in case the NTC fails or the relays stick closed.
If your brew thermoblock NTC or relay has failed, the group will still work but the water coming from it will be obviously boiling (thermostat cutoff is around 105-110C).
The thermostat will open and close like normal allowing the group to still be used.
Seeing as you mentioned that your coffee is very hot (assuming you're drinking an espresso or similar with no milk) this may be your problem. Check water flow from the group for any boiling and sputtering like I mentioned before.
If the steam boiler NTC or relay fails, chances are the thermal fuse will blow before the thermostat cuts in. It's quite rare for this NTC to fail.
I've seen the thermostats go open circuit and cause a no start up condition, this could be affecting your machine intermittently.
Why this issue persists after replacing the relays I'm not sure. It's possible to have a faulty triac but I haven't seen them be a cause of overheating or heating when switched off. They're only used to switch the lower power AC components (solenoid, steam pump, coffee pump).
Where did you source the relays and what are their ratings? I've never been able to find a supplier for the EM6910 relays.
When have access to a replacement PCB then swapping it across is the easier solution.
Thanks for that, noidle. Well boy-o did I hunt for the replacement relay.. I'm pretty sure that the company that made that exact part is phasing it out slowly. I only found a lot of 1000 (too many!) on mouser. So I went with a pair of pretty similar spec relays from RS. OJE-SS-112HM. I ordered them at 8AM and they arrived at my place by 4PM the very same day. Amazing! I'm in Sydney metro area though so that might explain it!
Well, funny story.. I just bought a pair of half working 6910s from gumtree for $50! The saga continues..... I guess I will try to make one great one from these three.
Those are the same relays I use for repair on EM7000 machines however the EM6910 relays use a 6V coil rather than a 12V coil.
Originally Posted by sitas
Not sure how the circuitry will cope with trying to switch a 12V relay when it's only designed for 6V. The lifespan would be a concern I think.
You should have some success getting a working machine from the lot I think.
I got another of the machines all booted up and warmed it (#2) and my original machine (#1) up together and did a little temperature experiment.
My hunch was that machine #1 was too hot. Long story short, it's pretty much exactly the temps that the other one is pouring at. This leads me to conclude that I was pretty much dead wrong! What are the odds of two machines being exactly as too-hot? Long odds.
I poured four shots from each machine, alternating the machine used to pour each shot. They were both accurate to within 1.5 degrees according to my food thermometer. No point in publishing any data as by now we know very well how much temperature is lost between the group head and the bottom of your vessel.
Doing some longer shots I noticed a (roughly) 10 degree drop over a 150ml pour.
Originally Posted by noidle22
I read somewhere else on here that the voltage at the switch was measured at 9V. My pair of 12V relays seem to be working fine alongside another machine.
Long Story Short: I F'd up!
After some experiments with my grinding method this morning, I realised what my big mistake may have been: I trusted the ground retention of my Mazzer too much, in fact the amount of grams which it retains can vary wildly from near zero to about 4 grams! Switching to a weigh-in post grind rather than pre at the cost of however many more beans I have to leave in the hopper overnight only to be drank by my early rising flatmate!
Thanks for your gracious assistance once more, CS users. But I think I got this one licked: CASE CLOSED
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