[Heathkit] SB-610 phase networks needed

[carl lowry]

Good Evening Ron,

The SB-610 scope which was the replacement to the HO-10 was
made between 1968 - 1972 by Heathkit. Thats over 35 some odd years ago.
I work on the SB-610 daily & have about 10 of them in here right now
to restore for folks
I have found that "all" resistors & caps have changed during these past 30 plus
years due to heat & simply age. The P.E.C. networks were made for Heathkit and
values are not shown in the manual. You really cannot purchase them
anywhere such as from Mouser,  etc. Got to go to the ARRL Handbooks
and figure out the two P.E.C. circuits.
May i offer a suggestion please. Replace "all" the resistors & caps in the area
around the particular tube V4 - 6J11 as no doubt the values have changes and are
allowing various voltages & capatances to be introduced into the two
circuits. The actual frequencies really are "no biggie" if they are slightly
off. I can provide you with a parts listing to order from Mouser, and I
can furnish you with a brand new Quad Cap replacement as i 
have 5 of those in here now.
When I work a SB-610 I replace & upgrade all resistors, caps, & diodes.
But best of luck & keep all of us posted.

73s

Carl, k4zrd


> From: k3pid at sbcglobal.net
> To: heathkit at mailman.qth.net
> Date: Fri, 21 Sep 2007 15:08:30 -0500
> Subject: [Heathkit] SB-610 phase networks needed
>
> I am restoring an SB-610 monitor scope and find that the two tone generator which is supposed to have frequencies of 1500 Hz and 1950 Hz have both shifted. I am reading about 1900 and 2350. The phase shift networks P.E.C 84-39 & 84-40 are the frequency determining components and my guess is that the internal capacitors have shifted enough to move the frequency. I realize that the exact frequency doesn't much matter as long as it is inside the passband but I would like to make it match the specification...
>
> Does anyone have these in NOS or if not then does anyone have the detailed specifications for the networks?
>
>
> Regards
> Ron H. - K3PID
>
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