I have a Dewalt DW340K hot air gun that has just decided to blow only
warm air whatever the position of the variable temperature setting control.

For that reason I don't think the element has failed - is it most likely
to be the triac?

I've ordered a triac (BTA12-600) as it's only a couple of quid. If that
doesn't fix it, is it worth bothering?

There are several other components on the control board but I don't know
if I can check them in circuit with just a multimeter. None look
obviously "blown".

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Reentrant

Reentrant wrote:
I have a Dewalt DW340K hot air gun that has just decided to blow only
warm air whatever the position of the variable temperature setting control.

For that reason I don't think the element has failed - is it most likely
to be the triac?

I've ordered a triac (BTA12-600) as it's only a couple of quid. If that
doesn't fix it, is it worth bothering?

There are several other components on the control board but I don't know
if I can check them in circuit with just a multimeter. None look
obviously "blown".

With no other info to go on, I'd have thought that a blown triac would
either be short circuit and therefore blowing at max heat irrespective
of setting or if it failed open circuit, then no heat at all.

Possibly more to do with the control cct that fires the triac perhaps.

A more analytical approach might bear fruit?

Bob

Don't know a lot about modern mains triac. I had an old dimmer once that
kind of went half dimmed, and in that case it was something called a diac, I
suspect nowadays its all duty cycle switched with some kind of IC though.
Life was a lot simpler before....
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
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"Reentrant" wrote in message
...
I have a Dewalt DW340K hot air gun that has just decided to blow only warm
air whatever the position of the variable temperature setting control.

For that reason I don't think the element has failed - is it most likely
to be the triac?

I've ordered a triac (BTA12-600) as it's only a couple of quid. If that
doesn't fix it, is it worth bothering?

There are several other components on the control board but I don't know
if I can check them in circuit with just a multimeter. None look obviously
"blown".

--
Reentrant

On 02/09/14 00:23, Brian Gaff wrote:
Don't know a lot about modern mains triac. I had an old dimmer once that
kind of went half dimmed, and in that case it was something called a diac, I
suspect nowadays its all duty cycle switched with some kind of IC though.
Life was a lot simpler before....

You would do half dimming with a diode rather than a diac.

The mechanics of AC power control are more or less unchanged[1] as a
triac is basically an AC thyristor so you only get the chance to say
when it turns on. It turns off on a zero crossing.

Chips usually offer some other features like ramp (soft) start and maybe
power-on to previous brightness and features like that.

[1] unless you use something like a GTO (gate turn off thyristor) or a
big FET or whatever the technology is used on train motive power control
these days. Then you can do high frequency chopping and have much nicer
control.

On Monday, September 1, 2014 1:02:31 PM UTC+1, Reentrant wrote:
I have a Dewalt DW340K hot air gun that has just decided to blow only

warm air whatever the position of the variable temperature setting control.



For that reason I don't think the element has failed - is it most likely

to be the triac?



I've ordered a triac (BTA12-600) as it's only a couple of quid. If that

doesn't fix it, is it worth bothering?



There are several other components on the control board but I don't know

if I can check them in circuit with just a multimeter. None look

obviously "blown".



--

Reentrant

I'm of the Been There Got .... etc school. Yes, it will be the triac from my experience, that is replacement brought the thing back to life again.

Great devices but I suspect they are no longer available. One feature of the design that intrigued me is that the motor is dc.

I don't know how much the OP uses the variable heat, but I use hot melt glue on occasions and find that works so much better if the gun is used at reduced heat to pre-heat the items to be assembled.

I bought it originally as I keep bees and thought the controllable hot air blast would be a good way to remove the cell cappings before honey extraction; possibly it does in a professional machine set up but it didn't when applied manually.

Rob

Tim Watts wrote:

You would do half dimming with a diode rather than a diac.
IME only if you want the lamp to explode!

On 02/09/2014 10:37, robgraham wrote:

I bought it originally as I keep bees and thought the controllable hot air blast would be a good way to remove the cell cappings before honey extraction; possibly it does in a professional machine set up but it didn't when applied manually.

Rob


Actually that's *exactly* what I was doing when it stopped working - I
thought I had some particularly stubborn cappings. It's also why I need
pretty accurate temperature control; I can't get on with an uncapping knife.

I've ordered the control IC too (a T2117) just in case, but unsoldering
the old one might be tricky.

If the repairs don't work I'll have to buy a new one pronto before the
EU restrict them to 100 watts.



--
Reentrant

On 02/09/14 13:50, Capitol wrote:
Tim Watts wrote:

You would do half dimming with a diode rather than a diac.
IME only if you want the lamp to explode!

Why would it explode?