[GreenKeys] Testing 255A Relay

[Bill Abate]

Tom,

I found the best way to test 255A polar relays was to use the military 
I-193A test set.  It has some really neat tools too. However the test 
set requires two properly adjusted relays to function.  What came first 
the chicken or the egg?  HI HI. Another piece of test equipment was the 
BE=77 and BE-77A units.  I never owned one of those and the instruction 
book never made me anxious to get one.

A simpler method I used was to use a TD with a RY tape, connected to a 
loop  supply and zero center milliamp meter.  When the relay is adjusted 
properly the meter needle will oscillate around the zero.  Not as 
accurate as with the 193A but it gets you close.

The 314  supposedly does not need (and physically can't) be adjusted.  
To me it was a throw away relay but I never had to do that. The RY tape 
will tell you if it works.

73,

Bill, K3PGB

> Date: Tue, 7 Feb 2023 08:59:16 -0500
> From: Tom Hunter <tomhenryhunter at gmail.com>
> To: GreenKeys at mailman.qth.net
> Subject: [GreenKeys] Testing 255A Relay
> Message-ID:
> 	<CAJK86937suuLBXybJFK8Odx5aPZVtXPyhmkY5DEBZ-K9m6EnjQ at mail.gmail.com>
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>
> Paul,
>
> I put one of my 255A Polar relays on the bench to go through a test on it.
> Pins 1 and 5 are numbered on the bottom. You can count down to the rest.
> The two coils on mine (pins 2 & 7 and and 3 & 6) each measured 128.6 ohms.
> Pin 1 shows continuity to the frame and  armature.  Pins 4 & 5 show
> continuity, each to a stationary contact. Pin 8 is not connected on mine.
>
> When I tested the contacts with an ohmmeter and moving the armature by hand
> they barely worked. A piece of bond paper cured that problem.
>
> A 1.5 V D cell was on one winding was enough to cause the armature to move.
> My relay is out of adjustment so I could only get it to move one way. If
> your relay is in adjustment reversing the polarity of the battery should
> get the armature to move the other way.
>
> The attached illustration is from the New RTTY Handbook. I could send you
> the adjustment procedure  from the same source if you need it. It worked
> for me on the 255A I am using with a military Dovetron.
>
> I am posting this to the group in the hope it may help others.
>
>
> Tom N3CRK
>