Freeze spray and hair dryer etiquette..

[JonathanAnon]

Just working on a TV at the moment, and I'm faced with the same situation a lot of you are also faced with no doubt......

TV wont power on, so you take the hairdryer to the back of the power supply and it magically comes on after a few seconds... However, this only gives you the general area of where the problematic component lies. Especially given that the components are so small nowadays.. Same issue when using the freeze spray (thought less so when using the straw)

I've tried a process of elimination using BOTH, but I never seem to be able to narrow it down to one component successfully.... Any tips or tricks that might help?

[stj]

Re: Freeze spray and hair dryer etiquette..

cardboard sheet to block area's you dont want to heat.

btw if it works when you warm it then it's either broken solder joints or a bad small capacitor.
because with silicon stuff it's the other way around - they work when they are cold.

btw if you get a cheap hot-air soldering unit they come with nozles down to 2.5mm
http://www.ebay.co.uk/itm/261434050278

[JonathanAnon]

Re: Freeze spray and hair dryer etiquette..

btw if it works when you warm it then it's either broken solder joints or a bad small capacitor.

Just curiuos as to why you would say "small" capacitor specifically. ?

[stj]

Re: Freeze spray and hair dryer etiquette..

because if you lose a few uf of capacitance from a 1000uf cap you dont notice - if you lose it from a 10uf cap it's a third gone.
and small caps are often part of the startup/feedback circuit and have a shorter rated lifespan.

[vinceroger69]

Re: Freeze spray and hair dryer etiquette..

because if you lose a few uf of capacitance from a 1000uf cap you dont notice - if you lose it from a 10uf cap it's a third gone.
and small caps are often part of the startup/feedback circuit and have a shorter rated lifespan.

totally agree had this on a good few repairs ive have done.

[SteveNielsen]

Re: Freeze spray and hair dryer etiquette..

Got me wondering, would a very low temp soldering tip work for a fast heat test of small parts?

[stj]

Re: Freeze spray and hair dryer etiquette..

risky, it's earthed.
if you put a thermal pad between the iron and part it should work - maybe a bit too well!

[SteveNielsen]

Re: Freeze spray and hair dryer etiquette..

As I thought, however I do recall it being done by a radio tech I worked with a very long time ago.

[stj]

Re: Freeze spray and hair dryer etiquette..

maybe his iron wasnt earthed.

my last one wasnt earthed, i put a 1meg resistor inline wih the earth so i could work on live wiring!

[SteveNielsen]

Re: Freeze spray and hair dryer etiquette..

I think it was an ESD-safe iron. He was heating up the face of TO-92 transistor. I asked him about it and he just said, "Don't worry about it!" It didn't matter what I ever asked him about though, that was always his answer.

[Topcat]

Re: Freeze spray and hair dryer etiquette..

I've got an Acer AL2423W that has this issue.....I've narrowed it down to the inverter board.....but can't pinpoint it.... Cold, no backlight. Once warm, either naturally or by hairdryer, works like a champ.......... I've reflowed the bastard till I'm blue in the face....

[stj]

Re: Freeze spray and hair dryer etiquette..

maybe there is a break in a coil and the heat is making it expand and connect.

[budm]

Re: Freeze spray and hair dryer etiquette..

Got me wondering, would a very low temp soldering tip work for a fast heat test of small parts?

Once you narrow down the area with hair dryer, then I use variable temp soldering iron for pin point, board unplugged of course.
I use Q-TIPS for localize cooling:
https://www.badcaps.net/forum/showth...NG+LN32B540P8D