Boiler and Coffee Cup Heaters on Monza 5010 not heating

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
robfincher

#1: Post by robfincher »

I'm trying to repair a Monza Deluxe 5010 for a friend. Neither the boiler nor coffee cup heaters are being energised, yet in other respects the machine appears to be working normally. The DC voltages at the SSR's for the heaters measures only 0.4 volts when the display reports "Heating". These voltages are not sufficient to drive the SSRs ON, but when I apply 6 VDC to the SSRs from an external source (with the control wires from the Gicar controller disconnected), the SSRs switch 230 VAC to the heaters. Both heaters then work as expected, and the machine will make coffee. The SSRs are driven by an STPIC6C595 8-bit shift register, which is controlled directly from the main microprocessor, so I thought the chip might be faulty. I replaced it with a new chip, but the problem persists.
A second problem exists too - the boiler feed pump runs continuously, and the machine needs to be turned off to avoid overheating of the pump.
If any one has any suggestions on how to proceed from here, I'd be glad to hear them!

JRising
Team HB

#2: Post by JRising »

And if you ground the boiler fill probe, the pump doesn't stop? It's not just the machine trying and failing to fill the boiler before turning on the heaters?

robfincher (original poster)

#3: Post by robfincher (original poster) »

Thanks for your reply. I've since found that the fundamental problem is the pump. I thought it was pumping, but it's just vibrating. I pulled it apart, all appeared OK, reassembled it and it worked. Then left it off for 30 minutes, turned it on again, and thereafter it wouldn't pump. So it seems the pump will need to be replaced - they're readily available in Australia and not too dear.
As for the boiler fill probe, shorting it to ground restored operation of the heaters, the pump kept vibrating but not pumping, and as a result the boiler water level never made it to the probe. So there was nothing wrong with the Gicar controller or the SSRs after all. I was a bit surprised at the simplicity of the probe, and wondered if our water here would be sufficiently conductive to signal the controller with a ground or near-ground. As it turned out, the controller would respond if the water resistance was less than about 350 kohm.
So when the new pump is fitted, I expect it will pump water into the boiler until water contacts the probe. Then the pump will stop and the heaters will start. I haven't yet figured out how the pump is restarted as the boiler water level drops during coffee making.
I also have to work out how to enter or change the password - I inadvertently set it to "Insert Password" when fiddling around with the touchpad - any thoughts?

JRising
Team HB

#4: Post by JRising »

robfincher wrote:As for the boiler fill probe, shorting it to ground restored operation of the heaters, the pump kept vibrating but not pumping, and as a result the boiler water level never made it to the probe. So there was nothing wrong with the Gicar controller or the SSRs after all.

I also have to work out how to enter or change the password - I inadvertently set it to "Insert Password" when fiddling around with the touchpad - any thoughts?
Excellent news about it just being a dead pump...

And a copy/paste from the manual...

could be specific to the machine that manual once belonged with, or a general password common to all of them. I don't know.

robfincher (original poster)

#5: Post by robfincher (original poster) »

Thanks for the info John. Somebody told me that the numbers 1 through 6 on the touchpad diagram in Chris' Coffee Service Owner's manual represent the numbers for the password. The password 23234 might be generic, or a factory reset - I'll know more when I get the machine working again with its new pump. Again, thanks for your interest, Rob

robfincher (original poster)

#6: Post by robfincher (original poster) »

Firstly I've successfully repaired the Monza 5010 machine - a new pump did the trick, and I've just made a fine cup of coffee with the Monza. As a guide to others, beware of pumps which vibrate, consume power, but don't actually pump water. I had such a pump, and replacement with a new one was the best option. At start up, the pump now fills the boiler, the rising water surface contacts the level probe, and the controller starts the warm-up process. The probe signal is key - without it the heater SSRs don't get energised so as to avoid heating without water in the heaters.

Secondly, there is a password factory reset option - information kindly supplied by Sam Nissen at Chris' Coffee. Start with the machine turned off, then press and hold the small and large cup buttons on the touchpad. Continue pressing both buttons, then turn the machine on. The downside to this process is that water dose, grind dose, temperatures etc are also reset to the factory settings, and will need to be reprogrammed to your own preference. I'm going to let the owner do this and to discover which password numbers correspond with which buttons on the touchpad.