Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newbie!)

[Rhothgar]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

looking at the board,
i would start by checking all the diodes for shorts.

I'll check those too.

I've borrow a book of a friend entitled "How to fix everything electronic". It appears at first glance to be broken down into a nice understandable format for the likes of me.

[Rhothgar]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

Just to make sure it's understood, checking components in circuit is fine for quick trouble-shooting but readings are often altered by other connected components in circuit. To be sure the parts should be tested out of circuit.

Understood.

Without seeing a schematic my educated guess is yes the open resistor could have caused the cap to fail, however the cap may have been ready to fail anyway so it could have been a combination of factors.

Cap tested fine out of circuit and appeared to be within tolerance.

[stj]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

looking at the board,
i would start by checking all the diodes for shorts.

[SteveNielsen]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

C8 is fine in circuit. I need to trust the Peak. However, I checked the resistor on the new PCB and it measured 17.8 Ohms ESR in circuit but the marking appear to be 47 Ohms hence the confusion.

The resistor on the broken board measures open with the Peak and as does C5.

What I am looking for is a reason why C5 would go from fine to open circuit in 20 seconds! Would the resistor have caused that because I had not noticed the resistor missing some of its covering before powering the board back up after having replaced C5?

Just to make sure it's understood, checking components in circuit is fine for quick trouble-shooting but readings are often altered by other connected components in circuit. To be sure the parts should be tested out of circuit.

Without seeing a schematic my educated guess is yes the open resistor could have caused the cap to fail, however the cap may have been ready to fail anyway so it could have been a combination of factors.

[SteveNielsen]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

You're right, it's 1%, my mistake.

[stj]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

http://www.ankaudiokits.com/resistorcodes.html

[stj]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

The resistor is 47 ohms, 5%

no it's not, it has a final brown stripe = 1%
the gold is a divisor.

[Rhothgar]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

I agree c5 should be replaced. I'd check c8 too.

The resistor is 47 ohms, 5%. Check it out of circuit.

C8 is fine in circuit. I need to trust the Peak. However, I checked the resistor on the new PCB and it measured 17.8 Ohms ESR in circuit but the marking appear to be 47 Ohms hence the confusion.

The resistor on the broken board measures open with the Peak and as does C5.

What I am looking for is a reason why C5 would go from fine to open circuit in 20 seconds! Would the resistor have caused that because I had not noticed the resistor missing some of its covering before powering the board back up after having replaced C5?

[SteveNielsen]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

I agree c5 should be replaced. I'd check c8 too.

The resistor is 47 ohms, 5%. Check it out of circuit.

[stj]

Re: Coffee Machine - YAY! I've blown my first capacitor (and a tip or two from a Newb

c5 is bad, the top is domed.

the blue resistor should meter 4.7 ohms i think.
you need to meter it for resistance - the peak esr meter can probably do it although it's not intended for that.

[Rhothgar]

Following my fridge post yesterday, I thought I would try desoldering.

I have a coffee machine which didn't switch on.

I could see C5 cap was blown so got another faulty board and desoldered the capacitor from that. Took me a good 30 minutes or so to remove my first ever cap. If anyone hadn't done this before, watch a few videos on YouTube first.

I doubt it is the best way to do it but I found lightly gripping the capacitor with a pair of pliers and loading the leads with fresh lead eventually worked.

First off I tried desolder braid on each leg individually. Man! That wastes so much time and resulted in failure.

When I finally removed cap, I checked it and it was within tolerance. Tools are important here ESPECIALLY if you are a newbie. I went out and bought solder braid and a no clean flux pen.

I wiped over the legs (which still had solder residue on with the flux pen). One leg would not go through the one hole so I located it and went over both solder pads with the flux pen and the mask in between.

I loaded up the iron and wipe back and forth across the holes whilst pressing the capacitor up towards the holes and seconds later pop, it seated and two defined pads of solder appeared! Brilliant! Well chuffed.

Now this is where I need advice.

I plugged the PCB back into coffee machine in workshop. Worked back to house and plugged in, reset and activate trip switch then reset again.

Walked back out to workshop (15 seconds) and the replaced capacitor was smoking. Switched off quick before it blew.

The coffee machine does not heat the thermoblock until you press a button so this circuit is live even though the machine appears not to be switched on. Not sure if that will give anyone any further clues.

On closer inspection, the blue resistor doesn't look too good.

Do any of the experts on here think that this could have caused the original failure and subsequent failure of the cap?

Capacitor is rated at 400V 2.2uF. Polarity was respected when recapping. Remember! I'm a newbie at this sort of stuff.

Can anyone tell me the rating of the blue resistor? I have used an app to try and identify it but I am not clear on which end to start from. I tried both but not convinced at result which states 47 Ohms 1% but one on new board, in-circuit measures 17.8 Ohms?