[Test-Equipment] HP-606A Calibration question

[Richard Knoppow]

----- Original Message ----- 
From: "Barry" <n4buq at knology.net>
To: <test-equipment at mailman.qth.net>
Sent: Tuesday, May 26, 2009 1:48 PM
Subject: Re: [Test-Equipment] HP-606A Calibration question


>> My experience has been different than Carls. While the
>> dials don't loosen up they are sometimes mis-set by 
>> careless
>> repair people.
>> The frequency calibration should come in to no worse
>> than half the spec, it is very good all over. The error 
>> is
>> determined by the characteristics of the tuning caps, 
>> they
>> are pretty accurate although I have some vague memory 
>> that
>> there were some bad ones. I have no idea of how the 
>> stators
>> on my generator got tilted, it would have taken a lot of
>> force, enough to damage a lot of other stuff and there 
>> was
>> no sign of that. Whoever bent the plates evidently didn't
>> realize that the stators were off or didn't know how to 
>> fix
>> that.
>> You should be able to get the calibration right on the
>> nose on one of the low bands and have it correct on all
>> bands once the L and C are done. Again, once the shield
>> cover is replaced the high end will need to be touched 
>> up.
>> Evidently the amount of disturbance to the amplifer is
>> little enough so it doesn't need touching up.
>> The dial slipping procedure is not in the manual, I
>> learned it at -hp-, it works. BTW, if you ever run across 
>> a
>> 608C/D they can also be brought exactly on the money. 
>> Both
>> generators were designed by Art Fong who was one of the
>> great designers at -hp- in the old days.
>> You are unblocked from my e-mail..
>>
>> --
>> Richard Knoppow
>
> Something occurred to me about all of this.  Is it 
> possible there is a proper starting position for the 
> trimmer so as to effect the
> final position of the slug?  In other words, there might 
> be almost any number of combinations of L and C that would 
> cause the endpoints
> to be on target, but certain combinations cause the 
> accuracy across the entire dial to be further off than 
> others?
>
> Barry - N4BUQ

    I don't think so. If the dial is set up correctly I 
would set the trimmer first and then see if the low end 
comes in. You have to juggle the L and the C anyway on all 
bands but this will give you a starting point if the high 
band coil has drifted off value. Set the slug about half way 
to it will be in the center of its range. Set the trimmer 
for the high end and then check the low end. If its out so 
much that you can't get it back with the slug then set the 
slug at the center and bend the coil, or rather, expand or 
compress it a bit to change the basic inductance. When its 
about on use the slug as a fine adjustment. Glue the thing 
down with coil dope and check it again after several hours 
to make sure the coil dope hasn't changed anything. Probably 
you will have to touch up the slug again. When the shield 
cover goes back on it will introduce some stray capacitance 
requiring all the trimmers to be touched up but usually does 
not affect the low end at all.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com