[Heathkit] SB-610 phase networks needed

Sat Sep 22 14:28:21 EDT 2007

I would like to express my personal thanks to Pete, WA2CWA, for all that he 
has done for the subscribers on various QTH.NET lists he is subscribed to. 
Besides being an outstanding source of original and reprinted Ham gear 
manuals, Pete has provided tech and historical info assistance to hundreds 
of Hams over the ten years I have known him. Thank you Pete!

For the rest of you: appreciate Pete, and all who do what he does for the 
hobby! Being a volunteer is way too often a thankless job. There are many of 
these lists who help all of us in one way or another. We all need to 
remember to thank them, appreciate them and return the favor when and where 
we can.

Others like W8UT, Al Parker, provide fantastic technical assistance. Al has 
done wonders with equipment most would have blown Taps for and pitched into 
a landfill.

The "only" pay these who provide assistance on any of these lists receive is 
the satisfaction of knowing that they have helped another Ham or radio 
hobbyist in need and the thanks they get from those who do thank them.

Thanks to "ALL" the helpers!

Duane Fischer, W8DBF/WPE8CXO
dfischer at usol.com
HHI: Halligan's Hallicrafters International
http://www.w9wze.net
HHRP: Historic Halligan Radio Project
hhrp.w9wze.net

----- Original Message ----- 
From: "Peter Markavage" <manualman at juno.com>
To: <Heathkit at mailman.qth.net>
Sent: Saturday, September 22, 2007 1:44 PM
Subject: Re: [Heathkit] SB-610 phase networks needed

> The bottom line is that it really doesn't make much difference if the
> output tone frequency has shifted due to component aging. It's a single
> or two tone test. As long as the tones are somewhere generally between 1K
> and 2K, the "test" can be done. Of course, if it's determined that the
> PEC has an internal component failure, then a re-build is necessary of
> the PEC.  The tones are not critical unless you have the desire to match
> the original specification. I built one out of discrete components years
> ago in the HO-10 when a lead broke off the PEC right at the substrate.
> Because of component tolerances, I think I was off by about 150 cycles.
> Life went on, and in time, I didn't even remember it wasn't exactly per
> the spec.
>
> Pete, wa2cwa
>
>
> On Sat, 22 Sep 2007 10:00:42 -0700 "Kenneth G. Gordon"
> <kgordon2006 at verizon.net> writes:
>> On 21 Sep 2007 at 15:08, K3PID wrote:
>>
>> > 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.
>>
>> Usually what happens with those PEC things is that the
>> resistors drift HIGH, although the capacitors usually don't
>> drift at all.
>>
>> > Does anyone have these in NOS or if not then does anyone have the
>> > detailed specifications for the networks?
>>
>> In some Heathkit rigs, the schematics show the values of
>> the components inside that PEC, and then one can be
>> made very easily out of discrete components. I do this
>> regularly for the SB/HW transceivers which use a PEC as
>> the tone generator for the CW sidetone.
>>
>> As I said, in every case I have examined so far, the
>> RESISTORS have drifted high, thereby raising the tone
>> frequency. One of the main culprits is the (usually) single
>> EXTERNAL resistor, which is also part of the phase-shift
>> network. In the SB/HW transceivers, it is the resistor
>> connecting the PEC to the tube.
>>
>> As Sandy mentioned, there is VERY little information on
>> designing those things. The math is not trivial, I might add...
>>
>> Ken Gordon W7EKB
> _______________________________________________
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
> $$ See the vintage area on the HCI web site - http://www.w9wze.org $$
> Heathkit mailing list
> Heathkit at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/heathkit
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.487 / Virus Database: 269.13.27/1020 - Release Date: 
> 9/20/2007 12:07 PM
>
> 