I own Synchronika for about a year and a half. Recently I feel that temperature is a bit higher and crema has become thicker and harder to control.
I suspect the machine is not completely clean even though I use RO water only.

Is there a way to clean the machine inside in a safe and recommended way?

I hear contradicting opinions about double boiler descaling. Synchronika has SS boilers. I would appreciate any maintenance and cleaning recommendations I should follow to keep the machine in optimal condition.

Taste aside, espresso machines require some mineral content in order to function properly. Their steam boiler fill probes, in particular, use the conductivity of water to detect the water level. With no dissolved solids, they'll overfill, giving you water instead of steam. You must add some mineral content back in. Third wave packets, raw water etc.

I would "Don't descale it if it doesn't need it". Look for scale, check the mushroom, check the boiler-fill-probe. If it's bad, then consider descaling.

As for suspecting that it's hotter than normal, what's hotter than normal? Is the display showing temperatures above the settings? Is the machine needing cooling flushes?

Are you suspecting that it's scaled in the return tube's fitting at the lower brew-boiler fitting because the coffee is seeming burnt and hotter than normal in the cup? This last one would be a reason to do a mild descaling of the brew circuit, just to see what comes out. If it's cloudy and colorful, then you'd know it needs something serious.

Thanks.

First, I use the RPavlis method (350g potassium on 4 ltr). This should be fine.
The machine itself has PID and it was set to 93C and reduce to 92C.

I will check the mushroom and boiler-fill-probe. It's a good idea. What is the boiler-fill-probe?

sbenyo wrote:I own Synchronika for about a year and a half. Recently I feel that temperature is a bit higher and crema has become thicker and harder to control. I suspect the machine is not completely clean even though I use RO water only.<snip>

I have a couple of observations. First, I think your issue likely has nothing to do with a dirty machine, unless you don't do regular cleaning of the group head.
Do you periodically measure the TDS of your RO water? If so, has it changed lately? Unless your RO is producing poor product water quality, you certainly don't need to descale. But, as suggested, it's easy to have a look by pulling the mushroom.
I agree with the observation that one need some minerals for best taste.
I disagree that you might need to add minerals for proper sensor operation. This is one of those theoretical things that is technically accurate, but which in the real world is rarely encountered. Unless your RO is producing 0 ppm TDS, which is unlikely, forget it. In any case, this is a steam boiler issue, not a brew boiler issue.
If your brew temperature is too hot for your liking, just turn it down a bit with the PID.
Your crema issue is more likely to be related to the coffee, not the machine, unless you're messing with very high or low brew pressures.
My 2-cents worth

The mushroom had a bit of residue in Dec 2021. I cleaned it at the time and now (since then) it looks perfect.
TDS from RO is not zero. It is around 16. With RPavlis it goes up to 60-70.

I can take the PID down to 91C. Still it's bothering me what causes the change. I am pretty sure something is different today.
I'll try to take video of the crema.