[Test-Equipment] HP-606A Calibration question

[Richard Knoppow]

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: <n4buq at knology.net>; "Discussion of Electronic Test 
Equipment" <test-equipment at mailman.qth.net>
Sent: Tuesday, May 26, 2009 1:21 PM
Subject: Re: [Test-Equipment] HP-606A Calibration question


> Barry, in that case you have no choice but to reset the 
> dial. As long as it
> is apart look for the orignal set screw marks.
>
> On the BCB range that you indicated earlier the linearity 
> can be well under
> spec. If necessary very carefully move plates for the 
> worse case band.
>
> On the ham bands or general coverage receivers the 606A 
> built in calibrator
> works great. The first time I used a 606A was at National 
> Radio when the
> GR-1000A's were replaced.
>
> I use a 606A and 8640B here, the 606 has better phase 
> noise performance and
> its a lot more convenient for general coverage receiver 
> alignment.
>
> Most 606 problems are 12B4's with leakage, other weak 
> tubes and a small
> electrolytic or so, usually in the modulator.
>
> Carl
>
    Well, you don't have to have it apart. The dial clamping 
screws are accessible when the main tuning knob is removed. 
Four screws there. Loosen them and the dial slips. No set 
screws anywhere.
    If the thing is way off center the dial. If its not far 
from center to begin with choose a direction and move it 
perhaps an eighth inch at the top and try to calibrate 
again. One way will make the center error larger and one 
will make it smaller. If you move too far it will have a 
reverse error. When finished make sure the clamp screws are 
tight.
    Again, make sure before you begin that the movable 
fiduciary is centered according to the marks on the front 
panel and lock it down with a bit of sticky tape at one 
corner.
    The only disassembly needed for a complete calibration 
and tuning is removal of the shield. This is a PITA if you 
don't have the original extra-long allen key. I had to make 
one.
    Touch up adjustment, where the frequencies are off just 
a bit at the high end can be done through the goof plug on 
the left side of the shield (facing the generator).
    I don't need to tell anyone here not to use metal allen 
keys on ferrite cores.

    I agree about the 12B4's, another trouble tube is the 
6CL6 which -hp- used in a lot of places. Check the regulator 
tubes by following the power supply test procedure using a 
Variac. Excessive variation can be caused by any of the 
regulator tubes but th 12B4's are offten the problem.


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