Telephone No. 312 with hesitant ring. - UK Vintage Radio Repair and Restoration Discussion Forum

SteveGC · 26th Dec 2016, 4:20 pm

Hi, enjoying reading through this great forum. I'm a complete newby regarding vintage phones so go easy on me chaps.

I have just taken possession of a 330L that seems to have 312 internals. It was refurbished in 62/2a. It works great with but the ringer is a little hesitant, and gets more so when left to ring for a few moments, slowing down. Checking inside shows no 3k resistor in place, but it has 500 ohm coils in place.

Can someone please explain to me the exact purpose of the resistor, and whether I need one with these 500 ohm coils. I assume the resistor lowers the power consumption of the ringer, for setups with multiple phones? My question is, do I need 2k coils to get a good vigorous ring or what?

I know this must be sure such basic stuff to you guys, but I'm finding it difficult to source a basic explanation of the workings of these great phones.

I attach a photo of my innards ��

Merry Christmas to you all.

Station X · 26th Dec 2016, 5:06 pm

I wouldn't worry about the lack of a 3.3k resistor at this stage.

Does the phone ring correctly when it is the ONLY phone connected to the line?

SteveGC · 26th Dec 2016, 6:21 pm

It doesnt make much difference if its the only telephone or not. The first couple of rings are the best, then it starts to struggle a little, getting just a bit hesitant, before breaking up and stuttering if left ringing for a few moments. In every other regard, it works perfectly. Dials out very nicely, no "noise" or crackling on received calls, which are bright and clear.
I dont mind it as it is. It is over 50 years old after all.
Just that every conversion tutorial ive read, they say you must use a 3.3k resistor.
There is a strap, between T11 and T10 that ive not seen mentioned anywhere, that is connected on my telephone. Removing that makes the ringer almost useless. The telephone came to me wired as you see it.

Station X · 26th Dec 2016, 6:43 pm

If the phone doesn't ring correctly when the phone is the only one connected to the line this shows that the fault has nothing to do with whether the resistor is fitted or not.

Check the mechanical adjustment of the bell.

TonyDuell · 26th Dec 2016, 6:54 pm

As regards that 3k3 resistor. It is quite in order to use a telephone without it if it's the only telephone on the line.

The original wiring scheme, as when the 300 series were made was to have a 1k bell in the telephone in series with a 2uF (or so) capacitor. Extension bells (or bells in other telephones on the same line) were wired in series with this bell. Each bell was 1k, you could have up to 4 of them. So (simplifying things, because DC resistance, which is what the 1k is, is not the same as impedance), you could have between 1k and 4k of bells and the single 2uF capacitor as the ringing circuit.

The 'New Plan' wiring scheme (plug-in telephones on the Plug 431A) has a single 1.8uF (much the same as 2uF here!) capacitor in the master socket. And 4k bells in the telephones (that's what an REN of 1 means, essentially). Again, up to 4 bells on the line, but now in parallel. So from 4k (1 telephone) to 1k (4 telephones in parallel) and the 1.8uF capacitor across the line for ringing. Much the same as before.

If you only have the one telephone connected, it can have a 1k bell. and no resistor. It's either the old scheme with 1 telephone or the new one with an REN of 4. But it should work. The resistor is a bodge, essentially, to increase the resistance of the bell and make it more like 4k. Needed to reduce the REN of the old-type telephones if you want several bells on the line.

SteveGC · 26th Dec 2016, 8:22 pm

Thanks for the replies folks. Ive adjusted the clapper so that it is just shy, [less than 1mm] from each bell when at rest. It sounds better now. Just a little weak maybe, but Im happy enough with it for now. Is there any other adjustment other than moving the bells? I see a cross head screw and the nuts on the end of the coils. I take it these are not adjustment points.Thank you Graham.
You explained it well Tony, thanks. I take it that the resistor has little effect on the ringer volume anyhow.

TonyDuell · 26th Dec 2016, 8:45 pm

The other adjustment is the gap between the armature and the core of the coil. It's set by sliding the magnet (the cylindrical metal bar between the 2 coils) through the yoke and locked by the large screw on top of the yoke. I forget what the correct setting is, though :-(

The resistor shouldn't have much effect on the volume. You can always try adding one to see the effect.

SteveGC · 26th Dec 2016, 9:12 pm

Thinking about it now, I dont think it needs any adjustment. The ends of the cores are such, that when in contact with the armature, the clapper ball is almost touching the bell as it should be. [ 0.5 mm or so] Same the other side. Increasing the gap between core and armature would mean the clapper would actually rest in contact with one bell or the other.
I will get some resistors and try it for my curiosity.

TonyDuell · 26th Dec 2016, 9:58 pm

The clapper certainly shouldn't touch the gong when stationary. If it does it will damp the ringing of the gong and sound dreadful.

From what I remember you set the gap between armature and coil cores first, then rotate the gongs (the fixing hole is not central) to give the right clearance between clapper and gong.

Pellseinydd · 26th Dec 2016, 10:55 pm

Quote:

Originally Posted by SteveGC

Thinking about it now, I dont think it needs any adjustment. The ends of the cores are such, that when in contact with the armature, the clapper ball is almost touching the bell as it should be. [ 0.5 mm or so] Same the other side. Increasing the gap between core and armature would mean the clapper would actually rest in contact with one bell or the other.
I will get some resistors and try it for my curiosity.

Steve

See http://www.britishtelephones.com/belladj1.htm fpr all you need to know about adjusting GPO bells. Your bell is a 'Bell 59A -unmounted' (500 ohm coils) - the one with 2 x 2000 ohm coils is the 'Bell 59D-unmounted' that doesn't need the 3.3K resistor. There is info there for adjusting to different ring frequencies used.

www.britishtelephones.com is the place to look for info on UK telephones.

Ian
CNet 0352 2345

SteveGC · 27th Dec 2016, 9:42 pm

Thanks Ian. What fantastic information on that site. Some things to check there.

26th Dec 2016, 4:20 pm	#1
SteveGC Retired Dormant Member Join Date: Dec 2016 Location: Stoke-on-Trent, West Midlands, UK. Posts: 5	Telephone No. 312 with hesitant ring. Hi, enjoying reading through this great forum. I'm a complete newby regarding vintage phones so go easy on me chaps. I have just taken possession of a 330L that seems to have 312 internals. It was refurbished in 62/2a. It works great with but the ringer is a little hesitant, and gets more so when left to ring for a few moments, slowing down. Checking inside shows no 3k resistor in place, but it has 500 ohm coils in place. Can someone please explain to me the exact purpose of the resistor, and whether I need one with these 500 ohm coils. I assume the resistor lowers the power consumption of the ringer, for setups with multiple phones? My question is, do I need 2k coils to get a good vigorous ring or what? I know this must be sure such basic stuff to you guys, but I'm finding it difficult to source a basic explanation of the workings of these great phones. I attach a photo of my innards �� Merry Christmas to you all. Attached Thumbnails

26th Dec 2016, 5:06 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Telephone No. 312 with hesitant ring. I wouldn't worry about the lack of a 3.3k resistor at this stage. Does the phone ring correctly when it is the ONLY phone connected to the line? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Dec 2016, 6:21 pm	#3
SteveGC Retired Dormant Member Join Date: Dec 2016 Location: Stoke-on-Trent, West Midlands, UK. Posts: 5	Re: Telephone No. 312 with hesitant ring. It doesnt make much difference if its the only telephone or not. The first couple of rings are the best, then it starts to struggle a little, getting just a bit hesitant, before breaking up and stuttering if left ringing for a few moments. In every other regard, it works perfectly. Dials out very nicely, no "noise" or crackling on received calls, which are bright and clear. I dont mind it as it is. It is over 50 years old after all. Just that every conversion tutorial ive read, they say you must use a 3.3k resistor. There is a strap, between T11 and T10 that ive not seen mentioned anywhere, that is connected on my telephone. Removing that makes the ringer almost useless. The telephone came to me wired as you see it.

26th Dec 2016, 6:43 pm	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Telephone No. 312 with hesitant ring. If the phone doesn't ring correctly when the phone is the only one connected to the line this shows that the fault has nothing to do with whether the resistor is fitted or not. Check the mechanical adjustment of the bell. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Dec 2016, 6:54 pm	#5
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Telephone No. 312 with hesitant ring. As regards that 3k3 resistor. It is quite in order to use a telephone without it if it's the only telephone on the line. The original wiring scheme, as when the 300 series were made was to have a 1k bell in the telephone in series with a 2uF (or so) capacitor. Extension bells (or bells in other telephones on the same line) were wired in series with this bell. Each bell was 1k, you could have up to 4 of them. So (simplifying things, because DC resistance, which is what the 1k is, is not the same as impedance), you could have between 1k and 4k of bells and the single 2uF capacitor as the ringing circuit. The 'New Plan' wiring scheme (plug-in telephones on the Plug 431A) has a single 1.8uF (much the same as 2uF here!) capacitor in the master socket. And 4k bells in the telephones (that's what an REN of 1 means, essentially). Again, up to 4 bells on the line, but now in parallel. So from 4k (1 telephone) to 1k (4 telephones in parallel) and the 1.8uF capacitor across the line for ringing. Much the same as before. If you only have the one telephone connected, it can have a 1k bell. and no resistor. It's either the old scheme with 1 telephone or the new one with an REN of 4. But it should work. The resistor is a bodge, essentially, to increase the resistance of the bell and make it more like 4k. Needed to reduce the REN of the old-type telephones if you want several bells on the line.

26th Dec 2016, 8:22 pm	#6
SteveGC Retired Dormant Member Join Date: Dec 2016 Location: Stoke-on-Trent, West Midlands, UK. Posts: 5	Re: Telephone No. 312 with hesitant ring. Thanks for the replies folks. Ive adjusted the clapper so that it is just shy, [less than 1mm] from each bell when at rest. It sounds better now. Just a little weak maybe, but Im happy enough with it for now. Is there any other adjustment other than moving the bells? I see a cross head screw and the nuts on the end of the coils. I take it these are not adjustment points.Thank you Graham. You explained it well Tony, thanks. I take it that the resistor has little effect on the ringer volume anyhow.

26th Dec 2016, 8:45 pm	#7
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Telephone No. 312 with hesitant ring. The other adjustment is the gap between the armature and the core of the coil. It's set by sliding the magnet (the cylindrical metal bar between the 2 coils) through the yoke and locked by the large screw on top of the yoke. I forget what the correct setting is, though :-( The resistor shouldn't have much effect on the volume. You can always try adding one to see the effect.

26th Dec 2016, 9:12 pm	#8
SteveGC Retired Dormant Member Join Date: Dec 2016 Location: Stoke-on-Trent, West Midlands, UK. Posts: 5	Re: Telephone No. 312 with hesitant ring. Thinking about it now, I dont think it needs any adjustment. The ends of the cores are such, that when in contact with the armature, the clapper ball is almost touching the bell as it should be. [ 0.5 mm or so] Same the other side. Increasing the gap between core and armature would mean the clapper would actually rest in contact with one bell or the other. I will get some resistors and try it for my curiosity.

26th Dec 2016, 9:58 pm	#9
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Telephone No. 312 with hesitant ring. The clapper certainly shouldn't touch the gong when stationary. If it does it will damp the ringing of the gong and sound dreadful. From what I remember you set the gap between armature and coil cores first, then rotate the gongs (the fixing hole is not central) to give the right clearance between clapper and gong.

27th Dec 2016, 9:42 pm	#11
SteveGC Retired Dormant Member Join Date: Dec 2016 Location: Stoke-on-Trent, West Midlands, UK. Posts: 5	Re: Telephone No. 312 with hesitant ring. Thanks Ian. What fantastic information on that site. Some things to check there.