Connecting to a W.E. 634A Subscriber Set

[Dennis Markham]

I know this may seem simple but I thought I'd run these connections by you guys that are more experienced in these older boxes.

I'm getting bell-tap when connected to the 634A.  Bill (Phonesrfun) suggested a leaking ringing capacitor.  Jorge suggested I could test that by connecting the 634A to a 425B (Model 500) network using the A & K terminals for the ringing capacitor.

I did connect the box to the 425B network block and the box continues to ring as it should.  However I continue to get bell-tap when dialing.  I tried with the Pekin Red Continental from my previous post

http://www.classicrotaryphones.com/forum/index.php?topic=1682.0

and also to make sure it wasn't the phone I connected my B1 to the box in place of the Continental.  I still get Bell-tap.

So as a last effort before I tell the owner he can live with the bell-tap, I thought I would post my connections to the 634A subset.  I believe they are correct but sometimes a different set of eyes can see the problem.

Here they are:

4 Conductor Desk Stand Cord

Red to "R" on the Induction Coil
Green to GN on the Induction Coil
Black to BK Terminal Strip
Yellow to Y or L2 on Induction Coil

Ringer Wires

Red Lead to L1
Black Lead to K on Terminal Strip

Ringer Capacitor

Connected to Y on Induction Coil
                     K on Terminal Strip

Condenser

Red Wire to "C" on Induction Coil
Black Wire to BK on Terminal Strip

Mounting Cord

Red to L1
Green to L2

Thanks for taking the time to look at these connections.

[Phonesrfun]

Dennis:

The ringer cap does not go to BK on the terminal strip.  It goes to K, along with the black ringer lead.

THis puts the ringer and the ringer condenser in series, and as a unit, they are bridged across the line L1 and L2.

-Bill

[Dennis Markham]

Bill, typo on my part.  The Ringing Capacitor is wired to K not BK.  I made a modification in my posting above.  So if that's the only error you see then it appears as though the rest of it is correct.

[Phonesrfun]

Yes, everything now is correct.

[Dennis Markham]

Thanks, Bill.  I give up.  The bell-tap will just have to be a part of the experience.

[Jester]

Dennis,

I have had to tweak the tension on the bias spring to cure bell tap on those 8A ringers.  I also noticed with one I had that it only did it if the subset was laid flat.  If I held the box upright, it wouldn't tap.

[Phonesrfun]

I can also send you a more modern version of a ringer cap to try out if you want.

[Dennis Markham]

Thanks Bill, I'll think about that offer.  I'm inclined now to pass.  Were this my set I was working on I'd try that. 

[bingster]

One thing further that you might try is to adjust the spacing of the gongs.  If I'm not mistaken, on that ringer both gongs are mounted eccentrically, so you should be able to move whichever gong is being struck out of the way by rotating it slightly.

[Dennis Markham]

Thanks Bingster. When I tried to adjust the gongs so that they were out of the way, then when it rings the ringing is poor, barely striking the gongs.  I also tried adjusting the bias tension spring/string but no luck there either.

[Bill]

I was under the impression that bell-tap could be cured, at least occasionally, by reversing the incoming red and green wires. If this is true, I'm sure you already tried it Dennis, so I'm adding the comment mostly for my own education. Any truth here, guys? I suppose it would tend to go along with the leaky-cap theory - a leaky cap would tend to bias the bell windings with a small DC component from the line.

Bill

[Dennis Markham]

Bill, I did try that as I "heard" that somewhere too.  Just for grins I'm going to once again try what Jorge suggested to confirm the leaky cap.  That was to connect the A & K terminals of a 425B (Model 500) network to the two terminals that currently connect the ringing capacitor.  At this moment I have the 634A connected to one of my phone jacks.  Each time I even pick up the handset in the other room I can hear the ding of the ringer box in the next room. 

[bingster]

I'm not sure how much you want to get into the nuts and bolts of the ringer assembly at this point, but this is a copy of BSP 3855 from 1917 that might help.  It deals with the adjustment of ringer assemblies, and applies to ringers that were common until the 302 type ringer came along.  It's possible that the air gaps mentioned in the BSP are out of spec, which would cause the more standard adjustments to have no effect.

Sorry about the quality--I don't have a scanner, so I had to photograph the pages.

AT&T 3855 Adjustment of Substation Apparatus 03/01/17

[Dennis Markham]

Thanks Bingster.  I will give it a look.  I hate to give up on this dumb thing...wait maybe it's not the thing that's dumb.

[bingster]

I just thought about another thing you might try, and this would rule out problems with the condenser and other subset parts:  Try switching out the actual ringer assembly with one from another subset.  If the second ringer doesn't tap, then the problem is in the first ringer, rather than it's associated parts.