Weller soldering iron.

[sigmolio]

Originally Posted by Station X

With the iron cold what resistance do you measure between the Live and Neutral pins of the mains plug? If you see an open circuit work your way round until you locate the break. My money's on dirty contacts.

I found a spare heating element and put that in. At the plug, without the iron tip inserted, and between live and neutral pins , I get 26M ohms rising to 36M ohms. With the tip in (and therefore the contacts closed) i get a steady 0.52kohms which I think is close to the value of just the heating element alone.
I have'nt plugged it in yet. I also resoldered the wires from the contacts.
I've attached a pic

[Station X]

That sounds good, but your original element had a resistance 0.538 kilohms ie 538R, so I don't understand why you've changed it.

[sigmolio]

Originally Posted by Station X

That sounds good, but your original element had a resistance 0.538 kilohms ie 538R, so I don't understand why you've changed it.

My apologies. I had an old iron on the bench (that also doesn't work) and gave you the wrong measurements.
From the figures I 've just given i'm wondering if I should plug it in.

[Craig Sawyers]

Quite. Mains powered. So for a 520 ohm heater resistance the power dissipated is (230^2)/520 = 102W, which is pretty much bang on for a 100W soldering iron.

Even if mains was at its (current) minimum of 230V - 6% (216.2V) the heater would dissipate 90W.

So there seems to have been nothing wrong with the original element.

Craig

[sigmolio]

Originally Posted by Station X

That sounds good, but your original element had a resistance 0.538 kilohms ie 538R, so I don't understand why you've changed it.

Also I have a Weller 200W which works fine.
At the plug, with the tip in it reads 262 ohms. Tip out it reads zero.`

[Station X]

262R fits in with it being 200W.

[MotorBikeLes]

Zero or infinite
Les.

[Station X]

Time to plug in the 100W iron methinks.

[sigmolio]

Originally Posted by MotorBikeLes

Zero or infinite
Les.

Gotta be infinite I guess.

[sigmolio]

Originally Posted by Station X

Time to plug in the 100W iron methinks.

Plugged it in without the tip, the barrel started to warm then the RCD tripped. I thought it could only heat up with the tip inserted.

[Station X]

If it's an RCD that's tripping that suggests an insulation breakdown, probably between the element and the iron's metal work. I assume a three core flex is fitted?

[sigmolio]

yes, 3 core flex

[Station X]

With the tip inserted you were able to read the resistance of the element between the live and neutral pins of the mains plug. Under the same conditions what resistance do you see between the Live/Neutral pins and the earth pin?

[sigmolio]

Thanks, can't check for about two hours.

[sigmolio]

Originally Posted by Station X

With the tip inserted you were able to read the resistance of the element between the live and neutral pins of the mains plug. Under the same conditions what resistance do you see between the Live/Neutral pins and the earth pin?

With the tip in : L to N 0.511k ohm
L to E 4.07M ohm
N to E 4.55M ohm

with the tip out L to N 0.529k ohms
L to E 3.94 M ohms
N to E 4.55 M ohms
many thanks

[MotorBikeLes]

Let me try an aside on this existing thread.
I want to take a 24v Weller TCP away with me, but don't want to pack the base unit.
Can I power it from a DC source (Wall wart or two car batts in series), or does the DC interfere with the control. Maybe polarity would effect sensing temp?
Thanks, Les.

[Leon Crampin]

The thermostat contacts will weld if used on a DC supply.

Leon.

[Craig Sawyers]

Why? What is the difference between 24V RMS AC and 24V DC?

Craig

[Vintage_RC]

Contact sparking/arcing is worse with DC as AC passes through zero 50/60 times per second extinguishing the arc.

[Leon Crampin]

100/120 times.

Leon.