[ARC5] Off topic - OS-8

Fri Jul 24 00:59:10 EDT 2015

KS designations were assigned by Western Electric to material they qualified for purchase from outside the Bell System (i.e. not manufactured by Western Electric). Most posts state that it stands for Kearny Specification, and that the designation was tied to the huge Western Electric Kearny Works manufacturing facility. But there were KS designations that predated the Kearny Works facility. Another post I came across stated KS stands for Kellogg Specification; Kellogg being a phone equipment manufacturer going back to some of the earliest days of the telephone. 
In any case, you are correct in that the KS designation had nothing to do with military systems. Interestingly, the Hickok 560 tube tester was used by the US Navy during the closing days of WW II, and were also used by Western Electric and given a KS designation.
Dave Rossetti410-279-0226 Mobile
Sent from my Verizon Wireless 4G LTE smartphone

-------- Original message --------
From: Jim Wiley <jwiley at gci.net> 
Date: 07/23/2015  11:03 PM  (GMT-05:00) 
To: David Rossetti <drossetti at comcast.net>, ARC5 at mailman.qth.net 
Subject: Re: [ARC5] Off topic - OS-8 

    Just a note of reminder: 
      Anything with a "KS" number is almost certainly something built
      for the Bell System, not the military.  These tub testers are Bell
      System items.  Doesn't really affect the price of tea in China,
      but just sayin'. 

      - Jim, KL7CC

    On 7/23/2015 4:44 PM, David Rossetti
      wrote:

      Got a Hickok 380A O-scope off of eBay very inexpensively, probably because
no one recognized it as a Hickok direct sale of the military OS-8 (Hickok
did that with some of their tube testers as well: e.g. the KS-15750 and the
RD 1575, the KS-15874-L2 and the nearly identical USM-118). Don't remember
exactly which version of the OS-8 it crossed to.

Have digital copies of the B and C OS-8 manuals and schematics harvested off
of the web. Contact me off-line if interested and I will send them to you.

Dave Rossetti
410-279-0226 (mobile)

-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Brian
Sent: Sunday, July 19, 2015 1:07 AM
To: kgordon2006 at frontier.com; ARC5 at mailman.qth.net
Subject: Re: [ARC5] Off topic - OS-8

Hello Ken,

The OS-8 series is a great little servicemen's portable CRO ... if you only
need to see up to 50 kHz. I have had several, and still have one (OS-8G/U),
though I fire up the TEK more frequently, now.

For me in Australia, the major limitation is the mains input Voltage. I got
around that by selecting a suitable capacitor to put in series with the
primary to get 240 Vac down to 110 Vac. I learned this trick when I was
teaching at Warwick University in the UK - we had all sorts of test
equipment from the US, and rather than increase the pressure on the floor
through extra iron, I built up a box with a switchable range of mains-rated
capacitors - I still have it ... somewhere. I could get the correct
capacitor value in seconds.

When you replace the selenium rectifiers with silicon, rather than double -
or even treble - your refurb work, just put one, carefully selected
capacitor in series with the primary.

The only other problem I had with this CRO was two, moderately large
resistors - 11 k as I recall, that drifted and took the picture off the face
of the Earth. If I had the manual, I could tell you where they were. An
electronic copy of the manual would be helpful ... pretty please?

73 de Brian, VK2GCE.

On Sunday, July 19, 2015 6:34 AM , you said:

In my stash of "stuff" I found two OS-8s: an OS-8 and an OS-8B.

I have manuals for both units.

Both "work" after a fashion, but the trace is skewed and not a
straight-line.

I suspect the main problem is in the power supply section.

Looking at the schematics, I see that there are three diodes, all selenium
rectifier types. It has been my experience that selenium-diodes become,
after a long while, not so much a diode, but a dual-resistor which shows a
bit less conductivity in one direction than another.

Therefore, I plan to replace them with modern diodes and a series resistor
to keep the voltage closer to the original voltage.

What is the group's experience with OS-8(X)?

Ken W7EKB

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