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From: Michael A. Terrell on 9 Mar 2005 17:02
Jim Yanik wrote:
>
> You could make a large plywood box,put a bank or two of 100W light bulbs in
> it,and a couple of fans drawing air out of the box,for a lot less,IMO.
> And size it large enough to fit a 7000 series scope mainframe.
> Gets too hot inside,unscrew a light bulb or two.
>
> Not fancy,but workable.
>
> --
> Jim Yanik
> jyanik
> at
> kua.net


Microdyne used 3 feet high by three feet deep by 8 feet wide plywood
boxes with 1500 watt heaters and an external thermostat mounted near the
exhaust. They worked, but we were required to add fire extinguishing
systems to the cabinets by the fire department. A radio caught fire
during burn-in and scorched the plywood. It was a sad sight. A new
$20,000 radio with several circuit boards burnt to bits of burnt
fiberglass and loose pieces of copper clad.
--
?

Michael A. Terrell
Central Florida
From: Jim Adney on 10 Mar 2005 18:42
On Wed, 09 Mar 2005 07:47:37 GMT "Michael A. Terrell"
<mike.terrell(a)earthlink.net> wrote:

> Jim, have you seen the small powder coat oven at Harbor Freight? The
>temperature range is too high, but it looks like a small environmental
>chamber. For the $399 price it wouldn't be hard to change or modify the
>controller to use for circuit boards, if needed.

You don't have to get fancy if you just need to do a single part (or a
few parts.) I've done wonders with a steel wastebasket and a small
light bulb. You adjust the temp by trying different size bulbs, and
you close off the wastebasket opening with alum foil, just to limit
air circulation, which would reduce the temp. Make sure the bulb is
placed so that it can't come in direct contact with the parts you're
drying out.

It doesn't have to be hot, just warm enough to make the vapor pressure
of the air low (ie, reduce the relative humidity.) 125-150F is plenty
warm.

-
-----------------------------------------------
Jim Adney jadney(a)vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------
From: Jim Yanik on 10 Mar 2005 19:33
Jim Adney <jadney(a)vwtype3.org> wrote in
news:5rjv21tgdc4csoj5f71jlfok03eg6onc4d(a)4ax.com:

> On Wed, 09 Mar 2005 07:47:37 GMT "Michael A. Terrell"
><mike.terrell(a)earthlink.net> wrote:
>
>> Jim, have you seen the small powder coat oven at Harbor Freight? The
>>temperature range is too high, but it looks like a small environmental
>>chamber. For the $399 price it wouldn't be hard to change or modify the
>>controller to use for circuit boards, if needed.

I think Mike is considering commercial uses,not home/hobby applications.
For that(commercial apps) it probably would be a good idea.
I'd want something larger,that I could put a whole instrument in after a
wash.

>
> You don't have to get fancy if you just need to do a single part (or a
> few parts.) I've done wonders with a steel wastebasket and a small
> light bulb. You adjust the temp by trying different size bulbs, and
> you close off the wastebasket opening with alum foil, just to limit
> air circulation, which would reduce the temp. Make sure the bulb is
> placed so that it can't come in direct contact with the parts you're
> drying out.
>
> It doesn't have to be hot, just warm enough to make the vapor pressure
> of the air low (ie, reduce the relative humidity.) 125-150F is plenty
> warm.

Actually,you do NOT want it any hotter than about 150degF, plastic parts
like cam drums begin to be affected.

And the muffin fans providing a slight negative pressure helps draw out the
moisture,increasing evaporation.

(BTW,I've also used the lightbulb/enclosure trick for curing epoxy.)


--
Jim Yanik
jyanik
at
kua.net
From: Michael A. Terrell on 11 Mar 2005 11:33
Jim Adney wrote:
>
> On Wed, 09 Mar 2005 07:47:37 GMT "Michael A. Terrell"
> <mike.terrell(a)earthlink.net> wrote:
>
> > Jim, have you seen the small powder coat oven at Harbor Freight? The
> >temperature range is too high, but it looks like a small environmental
> >chamber. For the $399 price it wouldn't be hard to change or modify the
> >controller to use for circuit boards, if needed.
>
> You don't have to get fancy if you just need to do a single part (or a
> few parts.) I've done wonders with a steel wastebasket and a small
> light bulb. You adjust the temp by trying different size bulbs, and
> you close off the wastebasket opening with alum foil, just to limit
> air circulation, which would reduce the temp. Make sure the bulb is
> placed so that it can't come in direct contact with the parts you're
> drying out.
>
> It doesn't have to be hot, just warm enough to make the vapor pressure
> of the air low (ie, reduce the relative humidity.) 125-150F is plenty
> warm.
>
> Jim Adney

I was thinking about baking large SMD ICs before soldering them in a
reflow oven, or with a hot air rework station. If you don't, that can
cause cracks in the moulded body and destroy the chip. I saw a couple
hundred $80 FIR chips destroyed by assembly because they ignored the
warning when the set up production of a new circuit board.

We also baked chips used by rework, then put a descant pack with the
chip in a modified carrier and heat sealed it in a moisture proof bag.

A few boards were built with a large chip turned 90 degrees (Or
more) The boards were backed prior to rework to lift and rotate the
part.

Repair of some equipment will move in this direction before you know
it.

--
?

Michael A. Terrell
Central Florida
From: Michael A. Terrell on 11 Mar 2005 11:40
Jim Yanik wrote:
>
> Jim Adney <jadney(a)vwtype3.org> wrote in
> news:5rjv21tgdc4csoj5f71jlfok03eg6onc4d(a)4ax.com:
>
> > On Wed, 09 Mar 2005 07:47:37 GMT "Michael A. Terrell"
> ><mike.terrell(a)earthlink.net> wrote:
> >
> >> Jim, have you seen the small powder coat oven at Harbor Freight? The
> >>temperature range is too high, but it looks like a small environmental
> >>chamber. For the $399 price it wouldn't be hard to change or modify the
> >>controller to use for circuit boards, if needed.
>
> I think Mike is considering commercial uses,not home/hobby applications.
> For that(commercial apps) it probably would be a good idea.
> I'd want something larger,that I could put a whole instrument in after a
> wash.
>
> >
> > You don't have to get fancy if you just need to do a single part (or a
> > few parts.) I've done wonders with a steel wastebasket and a small
> > light bulb. You adjust the temp by trying different size bulbs, and
> > you close off the wastebasket opening with alum foil, just to limit
> > air circulation, which would reduce the temp. Make sure the bulb is
> > placed so that it can't come in direct contact with the parts you're
> > drying out.
> >
> > It doesn't have to be hot, just warm enough to make the vapor pressure
> > of the air low (ie, reduce the relative humidity.) 125-150F is plenty
> > warm.
>
> Actually,you do NOT want it any hotter than about 150degF, plastic parts
> like cam drums begin to be affected.
>
> And the muffin fans providing a slight negative pressure helps draw out the
> moisture,increasing evaporation.
>
> (BTW,I've also used the lightbulb/enclosure trick for curing epoxy.)
>
> Jim Yanik


Yes, I was talking about professional use. I've looked at the oven
in the Ocala store. It would handle most circuit boards and small
equipment. I didn't have a tape measure with me to get the inside
dimensions. I would like one for my small shop to do multi layer
circuit board repairs, but those days are likely behind me.

--
?

Michael A. Terrell
Central Florida
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