Loud Pop In Receiver of 151AL Candlestick with 684A Subset

[gands-antiques]

I assembled this 151AL and 684A subset and when I was finished the wiring there is a loud pop in the receiver when the dial finger wheel returns to normal.

I substituted the capacitor on the 684A with a capacitor from a 302 but the popping didn't stop.  I swapped out the 684A with another 684A but the popping continued.

For some reason, when I jump L1 and R on the coil, the volume of the popping is reduced about 80% - 90%.

Below are the current wiring positions.  I've checked continuity of all wires and I've checked for any spades contacting each other and found none.

*BB and R on the dial are strapped. I disconnected the strap and it still pops.

Hookswitch:
B on hookswitch to B-Y to left terminal block
Y on hookswitch to Y on dial
YY-R on hookswitch to R on right terminal block

BB on hookswitch to BB on dial
Black from transmitter to BK on dial.

Transmitter:
BK from Transmitter to BK on dial (previously mentioned)
Other transmitter wire to YY-R on hookswitch

Receiver: 
Green to right terminal block GN
White to W on dial

From subset:
Green to GN right terminal block
Red to R on right terminal block
Yellow to B-Y on left terminal block
BK on strip to BK on dial 

Ringer:
Ringer Red to coil L1
Ringer Black to strip K

Condenser:
Condenser black to strip BK
Condenser red to coil C
Condenser grey to strip K
Condenser yellow to coil L2/Y

Line cord:
Red to L1 & Green to L2/Y

Any help will be appreciated.

Thanks,
Gary

[andre_janew]

I'd be tempted to run the leads of a varistor between L1 and R.

[gands-antiques]

I'd be tempted to run the leads of a varistor between L1 and R.

Thanks Andre,

I'm not familiar with a varistor. Will you please tell me what it is?

Thanks,
Gary

[poplar1]

I'd be tempted to run the leads of a varistor between L1 and R.

Varistors are standard on 500 sets, and can be seen on the back of a U-type receiver in a G-type handset.  You can probably get one cheap from someone who hotwires their candlestick phones using U1 or U3 or equivalent S-C/ITT/NE receiver units in repro receivers.

Varistor would go across GN and R on the induction coil here, in other words, in parallel with the receiver. Not across L1 and R.  Its purpose is to suppress the voltage spikes that cause "pops."

However, there may be another problem that's causing the pops in Gary's phone. Since the BB-W contacts break (open) first on the dial, and the BB-R contacts on the hookswitch break first, there should not be any noticeable pop either when hanging up or when dialing.

[unbeldi]

The L1 and R terminals are the leads of the primary winding of the induction coil.

Therefore you are shorting the primary winding, which essentially shorts the line for speech transmission and reception.
So clearly, a varistor solves nothing. It would be almost the same result, but the shorting resistance will vary with line current.

When you hear popping while the dial is operating, then it means that the receiver is not reconnected at the right time. It has to be the last circuit closed after the dial stops.  The W-BB contacts connect the receiver after the dial pulse switch has been permanently closed again.  Make sure the dial is wired correctly, and that the switches operate in the correct sequence.

[poplar1]

Gary, from what I can see in the photos, it's wired correctly. Do you hear the pop only when the dial returns, not when winding up the dial? And do you hear the dial pulses in the receiver? Do you hear a loud pop when slowly pushing down the hook?

Here's another test that should always be made before attempting to adjust contacts:
Remove the white receiver wire from W on the dial. Do you hear a pop when disconnecting the white wire, or reconnecting it?

[gands-antiques]

Thanks...

It pops only when dial returns (Not when winding the dial).

I don't hear the dial pulses in the receiver and there is no loud pop when the hook is slowly pushed down. There is a loud pop "sometimes"  when the receiver is lifted off of the hook (not every time though).

There is no popping when the white (W) wire is disconnected or reconnecting to the dial.

Thanks,
Gary

[unbeldi]

Looking at your pics now for the first time, it seems you don't have a 2A dial, but a 5H.

Did you install the required jumper between the R and BB terminals on the dial?

[poplar1]

Looking at your pics now for the first time, it seems you don't have a 2A dial, but a 5H.

Did you install the required jumper between the R and BB terminals on the dial?

"*BB and R on the dial are strapped. I disconnected the strap and it still pops."

See brown-yellow jumper from a 685A subset, used to strap BB and R.

[unbeldi]

"*BB and R on the dial are strapped. I disconnected the strap and it still pops."

See brown-yellow jumper from a 685A subset, used to strap BB and R.

oh, sorry, yes.  I had the image too much enlarged that the wire was not completely in my view.

[gands-antiques]

Yes, I have a jumper between BB and R.  I even disconnected the jumper to see if it would help with the popping and it didn't.

The only thing I have been able to do so far to help with the popping was to put a jumper between L1 and R on the coil. It reduced the popping by about 80% but I didn't try the transmission or reception quality when I had the jumper in place. This jumper has been removed.

Thanks,
Gary

[NorthernElectric]

Maybe the problem is with the contacts on your dial and this topic will help?  I think this is related to what unbeldi was referring to.

When you hear popping while the dial is operating, then it means that the receiver is not reconnected at the right time. It has to be the last circuit closed after the dial stops.  The W-BB contacts connect the receiver after the dial pulse switch has been permanently closed again.  Make sure the dial is wired correctly, and that the switches operate in the correct sequence.

[Phonesrfun]

Thanks...

It pops only when dial returns (Not when winding the dial).

I don't hear the dial pulses in the receiver and there is no loud pop when the hook is slowly pushed down. There is a loud pop "sometimes"  when the receiver is lifted off of the hook (not every time though).

There is no popping when the white (W) wire is disconnected or reconnecting to the dial.

Thanks,
Gary

With no popping when the dial is wound up, but a pop as it comes to rest, and with no popping when the white wire is removed from the dial,  I am wondering if the receiver contact (W-BB) of the dial is closing prematurely, just as the last digit of pulsing is being completed.  There should be a split second after the last pulse is done before the receiver switch turns the receiver back on.  If that is the case, the correction lies in adjusting the dial receiver switch contacts.

[Doug Rose]

I agree with Bill, I was going to say swap out the dial, it takes five minutes. JMHO....

On the other hand, thanks for the detailed pictures, I just got one yesterday!! ....Doug

[gands-antiques]

I want to thank everyone for all of the help with my popping 151AL.

I just fixed the popping issue by slightly bending the heavy bar "W" at the bottom of the pile up down 
(away from the governor).

The popping stopped and all functions of the phone are working properly.

Thanks again to everyone...I really appreciate it!!

Gary