Freezing components question

[Garydean]

I've never tried the spray freezing method for isolating bad components. Could someone please explain how to execute this method?

Thank you,

GD

[52 Bill]

It's simple really, if you have something that will act up only after it gets hot, you can use a can of freeze-spray to cool individual components to see if you can find the one that is causing the problem.

Most cans come with spray tubes so you can isolate the spray to either single components or to small areas.

Obviously, it cannot be used on anything that normally gets hot like tubes or power resistors, as the rapid temperature change will damage the components.

It really works best on transistors and IC's. Sometimes just blowing air through a drinking straw will work well enough to cool off an offending part.

[Garydean]

Thanks Bill,
So while I'm testing the amp and it starts to act up, freeze the components one by one till the symptom clears? When a component is bad, say a transistor or IC, will it always be hot?

[52 Bill]

So while I'm testing the amp and it starts to act up, freeze the components one by one till the symptom clears? When a component is bad, say a transistor or IC, will it always be hot?

This method will only work on components that have become thermally reactive, it is not a general troubleshooting technique. So no, not all bad transistors, etc. will be hot.

The thing to remember in all troubleshooting, isolating the problem circuit or components should be first on the list. Then heating and cooling components can be used as a method to find problems in those areas, just like taking voltage readings or looking at signal waveforms. It's just another means to an end.

I remember working on a blackface Fender Bassman head that as the owner described as having a real slow tremolo. Once warmed up (maybe 5 mins.) the volume of the amp would begin to rise and fall. Turned out to be a power supply diode that would open up when it got hot, and then re-connect when it cooled down.

I found the problem diode by substitution, but I could have used a cooling spray to freeze each diode until I found the one that would stop the cycling when it was cold.

[Enzo]

And thermal problems are not always about "getting hot." Most circuits warm up some after they have been on a little while. The difference between "cold" and normal operating temperature can be enough to cause trouble. A noisy transistor for example. Might not be overheating, but it gets noisy after a few minutes. Squirt some freezit on there and it shuts right up.

[Garydean]

Thanks guys for the lesson. Sounds like I need to get me some freezit.

Gary

[voxrules!]

Hi folks,
A member just had a thermal problem on his amp,( sorry but I don't know how to insert a link to his thread - If someone with a better forum' s experience than mine could explain to me how to do it I' d be thankful - anyway the thread number is 8655, and it ' s about a "white noise" problem ) and that' s the way he sorted out the defective component.

To me, while freezing sprays are not applicable in all cases, they' re very helpful indeed diagnosing "intermittent" problems, or generally in sorting problems arising some time after the amp' s been turned on...bet they spared thousands of severe headaches to many repairers around the world...It' s as simple as "point-spray-replace" so may God bless who invented / discovered ' em!

[BackwardsBoB]

Never allow programmers near your freeze mist. They only use it all up and talk insanity to your boss.