[Heathkit] SA-2040/2060 Antenna Tuner wattmeter calibration

[Tom Chesek]

I have a SA-2060A that had metering issues when I got it.  It also had a 
toasted antenna selection switch and was wired for one coax connection only. 
I found an adequate wafer switch from a Russian source on eBay but had to 
get creative with the contact wiring to give the same functionality as the 
original.  Also the original switch doubled up on switch contacts from both 
sides of the wafer whereas the replacement that I used only has contacts on 
one side of the wafer and I suppose that the power handling capacity is 
lower in my tuner because of it.  I use a SB -200 occasionally and have not 
had any further switch problems.

Now getting to the calibration issue...my tuner also had C105, a 1-8 pf 
trimmer, toasted in addition to the toasted switch mentioned above.  A 
direct sampling of the signal via C105 is added to the voltage picked up by 
the torroidal coil and "summed".  Adjustments made to C105 affect both sides 
of the bridge voltages so maybe a previous owner has calibrated the unit to 
his satisfaction via C105.  I do not have the privilege of owing a Bird 
meter so I made a rough calibration against a couple of Heath meters that I 
have.  I also compared the reading with the meter on my Yaesu FT-450.  I am 
certain that my tuner's meter doesn't fall within the Heath 5% accuracy but 
it is close enough.  It has been 2 or so years since I did this repair but I 
think that I got a trimmer cap from Mouser that was close in value.  I had 
to get a little creative in mounting it because it was not the same 
configuration as the original and I cannot access it through the hole in the 
case so any adjustment made means taking it apart and putting it back 
together.  You might be able to get away with adjusting C105 but if it is 
bad you will have to open the unit to get to things which is doable.  The 
original C105 is adjustable with a small slotted screwdriver via a small 
hole in one side of the switch/meter circuit assembly mounted on the rear of 
the tuner.

Good luck,

Tom K3TVC



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From: "Van K7VS" <wa7fab at cdsnet.net>
Sent: Tuesday, June 08, 2010 1:17 AM
To: "Heathkit Reflector" <heathkit at mailman.qth.net>
Subject: [Heathkit] SA-2040/2060 Antenna Tuner wattmeter calibration

> I have never seen this before in any of my heathkit antenna tuners that us
> the factory supplied swr bridge that comes aligned and ready for
> installation in the SA-2040/2060 and SA 2500 series but I just picked up
> another very nice SA-2060A that is extra clean inside and out and the only
> problem is the wattmeter when checked against my bird is way way low on
> indicated power output.  In both hi and low power position.  When I tried
> the set/swr proceedure I get the same indication as when just using the 
> two
> meters in "normal" position where the right one shows swr (which appears 
> to
> be accurate) and the left meter power output.  Has anyone run into this
> problem and I suspect I will have to take the swr bridge completely out in
> order to get the forward low and foward high calibration pots?  Am I right
> about that and has anyone had an sucess doing this and recalibrating the
> output power display??  Or is it a real bear! Thanks much.  Van, K7VS