Glitching out and mosfet overheating.

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8 months 1 week ago #10099 by Ian
The reason is simple: water hangs around a long time unless you dry it off with a gentle heat gun. I'm not aware of any chemical reason: Perhaps someone like Torsten knows more: he's in the trade.

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8 months 1 week ago #10100 by daddyfredregill
Doesn't isopropyl have some water in it as well?

Also Ian would you be able to send me a crystal and caps?

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8 months 1 week ago #10103 by Ty_Eeberfest
Yes, unless you are in a position where you can buy reagent grade chemicals any isopropyl you can get is 30% or 9% water. It dries pretty quickly though. Just try to keep it on the solder side of the board so it doesn't get underneath the parts too much.

For what it's worth, the last time I had anything to do with a board cleaning line (over 15 years ago) they were using water. The purpose of the cleaning process was to remove flux from populated boards after they went through the wave soldering process. The boards were totally immersed in hot DI water for several minutes in a tank with powerful ultrasonic agitation. The ultrasound was doing all the work, the water little more than a "carrier". After the ultrasonic tank the boards were dried with heated air. My point in all this being that the water did not harm the boards but measures were being taken to get them good and dry afterward.

Before ultrasonic cleaning in DI water all board cleaning / defluxing (that I am aware of) was done with a multi-step process that used trichloroethylene liguid and vapor. But the EPA decided trichloroethylene was bad (chlorinated solvent -> ozone depletion) so the industry moved to ultrasonic cleaning in more politically correct fluids.

Look into it later when the dust is clearing off the crater.

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8 months 1 week ago #10104 by Torsten Lang

Ian wrote: The reason is simple: water hangs around a long time unless you dry it off with a gentle heat gun. I'm not aware of any chemical reason: Perhaps someone like Torsten knows more: he's in the trade.

Hi,
what we're using for flux removal is 99.9% Isopropyl alcohol, soft, solvent resistent clothes with low lint content, and a not too soft brush.

But for the typical voltages used for Nixies or Thyratrons I didn't need much cleaning...

With best regards,
Torsten

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8 months 1 week ago #10105 by daddyfredregill
I got a new mofset installed and cleaned everything again. It is running good now.

The only thing i noticed is that the mosfet is getting a little warm. I can still leave my finger on it without feeling uncomfortable but i dont think it got this warm the last time I was running it.

Will switching from a 12v power supply to a 9v help?

There is a setting called HV target voltage. If I lower it wont the tubes dim.

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8 months 1 week ago #10106 by Ty_Eeberfest
Having the MOSFET running at the temperature you described is not something worth worrying about. It will never run stone cold as long as the laws of physics remain in force. If it really bothers you put a little heat sink on it. The data sheet say the IRF840 won't die until it hits 150*C (302*F)!

You could also experiment with the HV settings you mentioned but I doubt that will make much of a temperature difference (maybe a little tho). Will it dim the display? Maybe - depends on your tubes. Best to just try it and if you don't like the result you can put it back or do a factory reset.

Look into it later when the dust is clearing off the crater.

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