[GreenKeys] Model 28 RO Selective calling LP

[Jack]

I recall a lot of service calls for selective calling 28’s (Bell 83B3 systems)

where the function clutch would go bad and destroy all of the function

bars…there would be little pieces of black metal “teeth” all over

the place.  Even though we would always have a spare 83B3 typing

unit available, we would have to code the function bars for the particular station’s

ID’s. Of course, this always happened in the middle of the

night (thankfully, on double-overtime!).

 

Those cams on the stripper bail shaft were for timing. They were only used

on 83B3 “master site” TTY’s.  Some 83B3 systems had the master site

equipment in the base of an ASR and used the typing unit not only for

copy but to monitor incoming bids for traffic, etc. The master

panel had a stepper relay that was programmed for the call directing

codes, TD start codes, etc. The ASR’s TD would have an auxiliary

parallel-to-serial distributor wired to the stepper to generate

the codes on the loop. It was a marvel to watch and a nightmare to

troubleshoot, sitting on the floor, in the dark, and trying to see

through the grease and grime. Larger 83B3 systems had all of that stuff in a rack

with a dedicated 28 sequence selector to read the codes.

 

Jack

 

From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Kenneth Gartland
Sent: Friday, April 21, 2017 10:11 AM
To: greenkeys <GreenKeys at mailman.qth.net>
Subject: [GreenKeys] Model 28 RO Selective calling LP

 

Hi all!

 

Many thanks Jack for the great description of the selective 

calling operation on the 28LP's...

 

We had a couple of fellows in the shop who were looking

after most of the stunt box build ups for new installs and

day shift trouble calls...They were very good Tech's and

Really knew their stuff!

 

However, I did the night and weekend shifts, and inevitably 

there wud be a nasty failure of one or more of these select

call model 28 LP's...

 

The more function components installed in the stunt box,

the more "Loading" of the function clutch wud happen...

 

Usually, the clutch wud "Slip" during the reset stage of the cycle 

causing function levers to not withdraw from the codebars,

resulting in several function levers with broken, and/or bent

tines...

 

These were the most feared 28 calls of all...

 

As most stunt boxes were quite complex, there were never any

spares to field replace the typing unit...

 

To add to the misery, the main shaft driving gear would

usually strip out as well!

 

Brings back lotsa memories of really late nights...

 

Reading Jack's fine description of the process was very

worthy reading...

 

I did note in the M28 pictures, a solenoid & bracket mounted

behind and below the stripper bail blade...

 

There was some kind of cam with two lobes installed

on the stripper bail drive shaft, I am not familiar with this

set-up, can someone comment on this?

 

I can't recall seeing this before...

 

Thanks again Jack!

 

Ken

VE3-HMQ

 

 

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