It has been a few years since I opened up the B&W 2Q4 that was in the Heathkit SB-10 I used to own but I don't remember it being sealed at all.  I believe it was just crimped in the same 4 places around the bakelite base as was done with metal tubes.  Though they may have used different manufacturing methods over the years of production.  I remember I put a 1kHz signal into the unit and connected the 2 outputs into the X and Y channels of a scope to see how close it was to producing a 90 degree phase shift.  The display was slightly elliptical but didn't seem enough so to cause problems.  I also built a replica unit with precision resistors and silver mica capacitors that gave what appeared to be a perfect circle on the scope.

I do currently own a NOS Millen 75012 phase-shift unit that uses the same values of resistors and capacitors as the network in the GE article.  I opened it up to check the resistors.  All of the resistors are maroon Mepco 1% units of 100k and 133.3k value.  These all measured just within tolerance (one was 0.9% above nominal).  All of the components are mounted on a phenolic sheet with 4 compression trimmer capacitors paralleled with fixed capacitors.  I'll try to find some time to hook this unit up to a generator and scope like I did with the B&W unit to check its performance.

Sean W0KPX

On Tue, Jul 29, 2025 at 11:04 AM Jim Whartenby via Milsurplus <milsurplus@mailman.qth.net> wrote:
If you take a look at the 1961 GE SSB Handbook, PDF page 19, the SSB jr, uses a phase shift network.  See: 
The given resistor tolerances are 1%, the capacitors are paralleled with trimmers so a guess is that the capacitors need a similar tight tolerance.  How these resistor values have held up over 60 years plus is anyone's guess but they are certainly not carbon composition resistors.  The act of soldering a CC resistor will certainly change it's value making it unsuitable for use in the phase shift network.

Jim


Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy


On Tuesday, July 29, 2025 at 10:23:20 AM CDT, kgordon2006@frontier.com <kgordon2006@frontier.com> wrote:


On 29 Jul 2025 at 9:31, Mark K3MSB wrote:

>
> Hi Hue
>
> Were those octal phase shift networks hermetically sealed or in a vacuum?
>
> If either, then the resistors may be fine as they are not exposed to moisture.
>
> 73 Mark K3MSB 

They are hermetically sealsd, but not in a vacuumn. As I remember it, the resistor values are
NOT the common ones.

Ken W7EKB


>
>
>
> On Tue, Jul 29, 2025 at 4:38AM Hubert Miller <kargo_cult@msn.com> wrote:
>
> I have an unused B&W octal base, audio  phase shift thing like in this  xmtr. Knowing now about
> how miserably the old carbon resistors like to drift from nominal values, i do wonder how far off
> usable those phasing networks are now.
> -Hue Miller
>
>
> Sent from my Galaxy
>
>
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