Re: {Collins} Bird 82A

When I repaired my Bird 2500 watt load several years ago, I used Clearco
STO-50 silicone transformer oil, which was half the price that Bird was
asking.   However, the minimum order is 5 gallons.  My load only required 2
gallons, so I set aside a few ounces to keep on hand and sold the rest to
Larry W3LW who was also rebuilding a load.

The dielectric constant (permittivity) of STO-50 is 2.7, similar to the Dow
Corning oil that Bird resells.

Here's the spec sheet:


On Tue, Oct 10, 2017 at 3:20 PM, scottjohnson1 via Collins <
collins@xxxxxxxxxxxxx> wrote:

> Glen I would respectfully disagree.  I think the most important attribute
> would be dielectric constant, which is all over the map with respect to
> various transformer oils.  I think thermal conductivity is secondary,
> especially with Bird loads, which are very conservatively rated.  I do an
> s11 sweep with my HP 8510C van when I add or change oil, and mineral oil
> gives the lowest reflectivity.  It also has a fairly low vapor pressure, so
> it doesn't expand the rubber bellows any appreciable amount.
> Sent from my Verizon, Samsung Galaxy smartphone
> -------- Original message --------From: Glen Zook via Collins <
> collins@xxxxxxxxxxxxx> Date: 10/9/17  21:01  (GMT-07:00) To: Richard
> Solomon <w1ksz@xxxxxxxxxxx>, Collins Reflector <collins@xxxxxxxxxxxxx>
> Subject: Re: {Collins} Bird 82A
> You really need to use transformer oil and not "regular" mineral oil.
> Transformer oil is formulated to dissipate heat more than regular mineral
> oil can accomplish.

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