Another Telephone 706 problem.

[henry.crun]

I bought a 700 series phone from themuesum.co.uk in a fit of misplaced nostalgia - I'm a the avengers fan - & had it shipped to California wherein I reside. They included a BT/RJ11 adaptor, so plugging it into the hern????? telephone system was a done deal. The phone can dial out on my line, however it fails to ring for incoming calls.

Something I believe related (could be wrong) is my voice & physical noise from the cord rubbing against the housing transmit loudly into the earpiece. I can hear myself & my noise much clearer than I can hear my caller/callee.

Do these woes sound familiar to anyone?

Also, how does one open up this phone? There are two screws under the plunger on the cradle & that's it - none in the base. I took them out but got no further. Was I going about it the right way?

thanks

[russell_w_b]

Originally Posted by henry.crun

The phone can dial out on my line, however it fails to ring for incoming calls.

You may need to re-configure the 1u8 ringing capacitor within the telephone so that your incoming two wires (I don't know how a US telephone socket is wired) are connected to terms. T8 and T18, with T18 connected to T19, T17 and T16. Once you get inside the instrument, link Terms. T4, 5, 6 and 7 to each other, and Terms. T8 to T9. This connects the telephone bell via its internal bell-capacitor, like we used to use in the UK before the introduction of modular plug / socket telephone wiring and the part-separation of the bell circuit. Try it, anyway, to see if your telephone will ring. A US type 500 or 2500 telephone will ring on a UK system, so I don't see why it shouldn't be reciprocated.

Originally Posted by henry.crun

Something I believe related (could be wrong) is my voice & physical noise from the cord rubbing against the housing transmit loudly into the earpiece. I can hear myself & my noise much clearer than I can hear my caller/callee.

Do these woes sound familiar to anyone?

Are you sure the speech circuitry of a UK telephone is suitable for the US? I had speech problems with my ITT Kellogg 500 and 2500 US telephones here in the UK - or rather my wife did (I've a loud voice apparently, so no problem! ): the speech emanating from a US telephone was quieter than that of a UK one; I think the speech network is different to reflect higher gain in the US, and so the sidetone (a sniff of your own voice fed back to your receiver) will be different too. I also observe that on these little fibre - PSTN interface boxes one uses to put a POTS telephone circuit over a fibre link, there is a switch inside to select a US or a European voice network; good clue there...

Originally Posted by henry.crun

Also, how does one open up this phone? There are two screws under the plunger on the cradle & that's it - none in the base. I took them out but got no further. Was I going about it the right way?

Yes, you were. The screws are captive (usually!), so slacken them off as far as you can get, then push gently on the dial with your thumbs whilst, at the same time, lifting the edges of the casing at the sides with your fingers. Pull slightly towards you. A 706 Mk I (the older model with a solid coloured dial and chromium screw-escutcheons around the cradle switch) should lift off. A more modern 706 Mk II with a plastic handle beneath the handset may have a couple of protrusions at the front of the case that slot into the steel base (like a 746) and so may need to come towards you a little more.

[Tim]

Are you sure the speech circuitry of a UK telephone is suitable for the US?

Fine, I have done a couple now and they worked perfectly.
Even the MF dialing is the same!
As far as I am aware the US system is a two wire one, with ringing derived locally from within the telephone(similar to old british system). If your 706 has been converted to UK plug and socket, it will need "unconverting" to work properly.(As in Russels post above.)
Good luck!
Tim

[henry.crun]

Originally Posted by russell_w_b

and so the sidetone (a sniff of your own voice fed back to your receiver) will be different too.

thanks for the other feedback. the issue with the sidetone is it's excessive. my caller/callee has no (apparent) difficulty hearing me. i just hear too much of me & my extraneous noises. is there a way of toning down the sidetone?

thanks again

by the way, the phone is currently on my photoblog heavily photoshopped with some explanatory audio (courtesy of spike milligan & peter sellers).

Originally Posted by henry.crun

... the hern?? telephone system ...

For those who were wondering, hern is explained at http://en.wikipedia.org/wiki/Hern Other uses.

[russell_w_b]

Originally Posted by henry.crun

thanks for the other feedback. the issue with the sidetone is it's excessive. my caller/callee has no (apparent) difficulty hearing me. i just hear too much of me & my extraneous noises. is there a way of toning down the sidetone?

What's the DC voltage measured across your incoming line terminals when the receiver is off-hook?

[Mister C]

Just to add to Russel's notes on how to remove the case - sometimes the case (or the dial surround ring) catches on the dial finger plate and can make it difficult to get the case off. If so, you might want to try removing the finger plate to avoid damage.

Take a short length of adhesive tape (sellotape), stick this to the clear plastic dial label cover in the centre of the dial, and then pull towards you sharply. It may take a couple of goes (if you've got anything with a small suction cup on the end of it, you can pull the centre out with that instead). Remove the dial label and then remove the single screw in the centre of the dial to lift the finger plate off.

[dagskarlsen]

Originally Posted by henry.crun

thanks for the other feedback. the issue with the sidetone is it's excessive. my caller/callee has no (apparent) difficulty hearing me. i just hear too much of me & my extraneous noises. is there a way of toning down the sidetone?

thanks again

by the way, the phone is currently on my photoblog heavily photoshopped with some explanatory audio (courtesy of spike milligan & peter sellers).

For those who were wondering, hern is explained at http://en.wikipedia.org/wiki/Hern Other uses.

We use to have the opisit problem in Europe, the US (modern (post 1950)) telephones has a weaker level from the transmitter than we are used to.

You may try to bridge the transmitter with a resistor, try different values until it works OK.

dsk

[henry.crun]

Thanks for all the replies. I'm off to Radio Shack for a voltmeter & then I'll put on my mask & open Crun's Telephone Surgery for business. Hope, with your hints, to put it right & that the patient doesn't die on the operating table ...

[mawdsjeff]

the regulator may be faulty, or reversed in its' socket, (which takes it out of service). This could cause excessive sidetone.

[henry.crun]

Originally Posted by mawdsjeff

the regulator may be faulty, or reversed in its socket, (which takes it out of service). This could cause excessive sidetone.

The regulator is the small circuit board standing up between the plunger supports? In my phone, the capacitors on that board are facing the dial. Is that the correct orientation? Perhaps this photo helps?

[henry.crun]

Following the logic in a neighbouring thread, I tried to reverse the regulator in my phone. However it appears to have mated with the main board for life. Any hints on how to remove it without breaking either it or the main board?

(Before attempting this, I took the receiver off hook & put it on my desk & got a nasty screech of feedback for my troubles.)

[Dave Moll]

Originally Posted by henry.crun

I took the receiver off hook & put it on my desk & got a nasty screech of feedback

By this, I assume you mean that you left it off-hook for some time and received the "howler" tone designed to warn the user that the handset has not been replaced correctly and they have failed to respond to that lady who tells them to "please hang up and try again".

[henry.crun]

Originally Posted by Dave Moll

By this, I assume you mean that you left it off-hook for some time and received the "howler" tone designed to warn the user that the handset has not been replaced correctly and they have failed to respond to that lady who tells them to "please hang up and try again".

No, I took the receiver off hook & as I placed it on the desk, it screeched in genuine very obnoxious feedback - no chance for the nice machines of Pacbell (now actually AT&T - again) to do their howler tones.

[henry.crun]

Would a failed regulator also cause the fail in the ringer?

[russell_w_b]

Originally Posted by henry.crun

Would a failed regulator also cause the fail in the ringer?

No.

Incidentally, I've had 'howl-around' on an 'Ascom Berkshire' modern push-button analogue telephone, simply by plonking the handset on the desk. The phone was connected to a POTS-Fibre converter at the time, effectively simulating an exchange two yards away!

Try spraying a little penetrating fluid down the slot of the regulator, leaving it awhile, then rocking it - very gently! - from side-to-side at the top.

Have you managed to measure the off-hook DC voltage at your incoming line yet?

[Herald1360]

Howl round like that is a nice illustration of the "gain" of a carbon microphone capsule. It's perfectly possible to make an amplifier using a moving armature headphone coupled directly to a carbon microphone capsule, The noise and distortion performance is pretty poor, but there's no shortage of power gain between signal in and signal out.

ISTR most field telephones will screech if you hang onto the pressel switch whilst placing the handset in its cradle. I guess pretty much anything that directs the sound from the earpiece towards the microphone better than free space or a head in the way will do.

Chris

[henry.crun]

Originally Posted by russell_w_b

Have you managed to measure the off-hook DC voltage at your incoming line yet?

According to my meter, the off-hook DC voltage is 70V. Got this result from poking Terms 5 & 18 & setting the meter to its 20V range. Does that sound like a plausible value? Given Google says AT&T line voltage is 48V I must be poking the wrong things ...

Thanks

[russell_w_b]

Originally Posted by henry.crun

According to my meter, the off-hook DC voltage is 70V.

Bldy Hll?! Are you sure that's the 'off-hook' voltage (handset lifted) and not the 'on-hook' voltage (handset on cradle)? No wonder you're getting feedback and loud side-tone!

We're looking for about 12V here. Sure, 48 - 90(maybe in the U.S)V 'on-hook', but that should drop significantly when the handset is lifted.

Merry Christmas!

[Station X]

The line voltage (on-hook or off-hook) should be measured between terminals T18 and T8.

For the bell to ring it requires a capacitor to be connected in series with it. When these phones were hard wired to the line the capacitor was connected between T7 and T9. The capacitor is still there, but has been disconnected so that the phone can be used on a plug and socket system.

The UK plug and socket system has the capacitor in the master jack and its leads are extended to all slave jacks by internal house wiring. The capacitor sits between the blue and red wires of the line cord.

I don't know how US phone sockets are wired, but for this phone to work there must be a capacitor between the blue and red wires. You could try the experiment of connecting T6 to T7 and T8 to T9. This will reconnect the internal capacitor. If the bell now rings you have a problem with the house wiring.

[henry.crun]

Originally Posted by Station X

The line voltage (on-hook or off-hook) should be measured between terminals T18 and T8.

Measuring across T18 and T8, I see 50V off-hook & 47.5V on-hook.