Expobar Office Control: Houston, We Have A Problem! - Page 2

Need help with equipment usage or want to share your latest discovery?
User avatar
old442
Posts: 120
Joined: 17 years ago

#11: Post by old442 »

erics wrote:I'm just guessing here cause I'm not familar with the Expobar either BUT the item you are referring to as the "control board" is simply(?) a series of membrane switches. The real action takes place in the Gicar controller to which that wiring harness from the "control board" goes to.
Actually, the control board with the membrane switches is the Gicar controller. I'm not sure if it has the power relay for the heater as mine has a separate large relay for this.
Kurt
LMWDP 114

User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#12: Post by Woz (original poster) »

I accessed the Gicar controller and got a look inside. damage appears very localized and no other damage to the controller is evident. Only the one pin in the controller shows damage as you can see in these shots.




Since the heat shrink was loose, I am thinking an errant drop of water may have fell just right to fall inside.

Advertisement
User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#13: Post by Woz (original poster) »

old442 wrote:Actually, the control board with the membrane switches is the Gicar controller. I'm not sure if it has the power relay for the heater as mine has a separate large relay for this.

PM sent regarding parts

User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#14: Post by Woz (original poster) »

The red wire that feeds that connector comes directly from the thermostat. What should I read if I ohm out the thermostat?

JonS
Posts: 53
Joined: 17 years ago

#15: Post by JonS replying to Woz »

The thermostat is in series with the boiler element. You would expect this to be zero ohm (or thereabouts) unless it had been tripped due to over-temperature. If that's not the case, and pressing the red reset button doesn't cure it, then I would say it's broken.

[EDIT: Oh bugger, I forgot when I wrote the rest of this, that you'd already posted that you'd checked the heater element, and it was fine. Christ, I have a memory like a sieve - comes from too many sleep-deprived nights with a little baby in the house :oops: Now I'm really stumped.

Out of interest, when you checked the heater element, what was its resistance ?

I guess maybe it could be a very localised moisture short on the control board after all]


If the red wire from the controller goes to the thermostat, then I would anticipate this is the live feed for the boiler element, straight from the relay on the controller board. Have you checked the resistance of the boiler element yet, after disconnecting the wires from it ?

I'm in two minds about this:

1. The boiler element has failed, but gone short-circuit rather than open-circuit.

A large current has flowed as a result, and the first point of failure is the heater relay on the control board. That being the case, verifiable by checking out the boiler element, and unless you find anything else in that particular circuit path that seems suspect, then you're going to need a new element, and a new control board (or at least a new relay fitting, whichever's easiest)

Heater elements do fail, it's as simple as that. If the pressurestat had failed, then I'd have expected the thermostat to protect the element (unless that's faulty too)

2. The moisture-causing-short-circuit theory

Also a possibility, in which case, you should find no problem with the element, or any of the other parts in that circuit path. The damage would likely be isolated to the output relay of the control board (and the burned connector)

My money is currently on (1) though others more familiar with your specific machine may know better.

Hope this helps.

Jon

User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#16: Post by Woz (original poster) »

Thanks Jon. Sorry to hear about your sleep depravity :)

The heater read at 14 ohms. The thermostat does indeed read zero, so it may be just fine.

I don't have a handy new connector laying around, so I tried to clear debris and clean up my damaged one to see if I could make a good connection and discover if the machine would work. The connector didn't want to seat well in the socket, so at one point I tried pushing on it and got a little bite from a wire on the opposite side. Power is definitely reaching it.

JonS
Posts: 53
Joined: 17 years ago

#17: Post by JonS »

Thanks Jon. Sorry to hear about your sleep depravity :)
Hmm, tell me about it. I've never been right since we had kids :?

I think the safest bet, if you haven't already, would be what erics suggested, to get hold of the official schematic for your actual machine so you have an accurate reference. There's no harm in persuing the problem yourself (as long as you're careful with the voltages, etc.), but it's getting harder to offer advice not knowing exactly what the circuit looks like.

I might be missing something obvious, but you have 2 main pieces of evidence to go on:

1. No heat
2. A charred connector, at the controller, in the boiler circuit path

The element resistance sounds in the right sort of ballpark - it's neither open circuit nor short. Rough guesstimates: My Isomac element is ~37 ohm on a 230v machine. 230 * 230 / 37 = ~1400w, so for you 110 * 110 / 14 = 864w. This sounds a fair bit lower than the UK office control machine, but perhaps the US ones are lower rated anyway to keep the current draw under control.

You say there's voltage at the connector 'cos you got a shock (for god's sake be careful. A misspent youth building and modding guitar amplifiers got me plenty of shocks and burns, but it only takes one to kill you). Keep your left hand in your pocket when you're messing with live equipment, seriously, never use both hands.

It also seems like you've validated the out-of-circuit behaviour of the various components in the boiler heating circuit.

Have you tried (carefully!) measuring the voltages at the pins of the various components in the brew circuit, starting at the controller connector end so you know that it's making it all the way through ? Clip one meter probe onto neutral, then just probe the pins with the other meter probe. With a cold machine, you would expect to get voltage all the way through to the live side of the boiler element, the other side already being connected to neutral. The point where the voltage no-longer gets through would indicate the guilty component or connection.

I'm honestly wracking my brains for other suggestions as to how best to narrow it down further, but it's really difficult without the machine or an accurate schematic to work with.

BTW, I'm looking back over the thread, looking at the pictures of that charred connector. In the first picture it looks like it's a really bad fit, all lifted at one end, the end that's burned. Did you lift it out like that, or is that exactly how you found it ? In the other pictures it looks pretty charred. Is it possible that it's never been a particularly good connection, and has been arcing away ? This being the case, it's always possible that the connection is simply so burned up it's not even passing current any more, which is why nothing's reaching the heater. Check the voltages in the boiler circuit as I outlined above, and see if voltage is even making it out of the connector itself. I know you got a shock, but if you can, do a proper sanity check with a volt meter on the actual circuit board pin for that end of the connector as well.

Jon

Advertisement
User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#18: Post by Woz (original poster) »

Thanks Jon. Never underestimate your safety when working with electronics. There was no exposed metal on that connector, the insolation of each wire extends into the connector, but I got a shock anyway.

The first picture shows exactly the way I found it. It was dislodged and pushed away. I tested the thermostat, the first location in the path of that red wire, and there is no power. So, it would seem power is going in to the connector and some must be getting out also (to the pump for instance). However, power is not leaving through that scorched connector.

WLL was very helpful when I called the other day and the emailed me two schematics: one hydraulic showing all components and one electrical.
Here is a link for download:
http://download.yousendit.com/2AD6B85A6723CEFC

User avatar
Woz (original poster)
Posts: 27
Joined: 17 years ago

#19: Post by Woz (original poster) »

Oh, also, Chris had told me to expect about 8.3 ohms on the heater which he expected to be similar to an Isomac. 14 was more than I was expecting!

JonS
Posts: 53
Joined: 17 years ago

#20: Post by JonS »

Woz wrote: I tested the thermostat, the first location in the path of that red wire, and there is no power. So, it would seem power is going in to the connector and some must be getting out also (to the pump for instance). However, power is not leaving through that scorched connector.
So, are you able to gain access to the solder pad (the one to the left of the "CN5" writing) where the scorched connector pin is soldered to the circuit board, while power is applied ?



I'm trying to ascertain where exactly the power stops getting through. Either the connector pin itself has had it, or the heater relay (RL3 in the picture, from the looks of it) is screwed (or maybe there's an additional problem with the control input to the heater relay perhaps)

Jon