Thorn Ericsson "Diavox" (TSR 8003 "Astrofon") rewiring

[snathe1978]

Hi everyone.

I've just acquired a Thorn Ericsson "Diavox" - otherwise known as an Astrofon from the Post Office's "Special Range" telephones in the early 80s.

It seems to be a much later model than the SR versions released over here in the 1980s in that it has a tone caller (adjustable for volume and pitch) as opposed to a bell, and it has a MF keypad instead of LD, so I assume it handles MF dialling.

I say "assume" as it came to me without a connected line cord; it had been cut off outside the phone at some stage and disconnected internally so none of the 4 internal wires were connected to any of the terminals.
Interestingly enough, there is a BT "Green circle" sticker on the bottom and a BABT label as well, both of which look to be original from manufacture date, so I also assume that this was actually once a fully functional phone that was used here in the UK (see image 2 below - this also shows it was manufactured in 1987 in the UK).

I'm now trying to re-connect a standard PST line cord to it but without any success. I'm using the rewiring instructions for a TSR1003 from Bob's Telephone File (http://www.britishtelephones.com/pstconv1.htm#1003) as a starting point however I'm confused in that only 9 terminals are listed on the rewiring instructions, yet on the phone there are 12 in total (9 down the left hand side and 3 along the bottom) - you can hopefully see these in images 3 and 4 and this also shows how the handset and tone caller are currently wired (the red, yellow, black and white wires together are the handset, the two seperate white wires along the bottom are the tone caller).

If I connect the line cord wires as per the instructions (taking terminal 9 as the top and counting vertically down to terminal 1 at the bottom, ignoring the terminals along the bottom edge) I get continuous dialling tone whether the handset is on or off hook, and the keypad does not produce any tones. I don't have a thermistor 1A-1 to hand so am unable to complete that part, however just strapping terminals 2 and 5 does not make any difference to the above so I don't know whether it would make any difference.

I've included an image of the underside of the PCB (it's been turned so that the top is still top, if you see what I mean) if that makes it any clearer - unfortunately it's all a bit beyond my limited ken!

It's probably a long shot, but does anyone know how this particular Astrofon model needs to be wired up in order to make it fully functional again?

Thanks in advance, and apologies for the essay-like post!

Nathan.

[dagskarlsen]

Never seen this before, but by looking at the PCB I would guess that number 9 is the bell wire, and 8 and 7 is the line wires. If not I would try to connect one of the line wires to no 7, and test with the close to terminals one by one if I get dial tone, and breakes it when going on hook.

[snathe1978]

OK, I've had a bit of a tinker just now following dagskarlsen's suggestions and by connecting the white wire to terminal 7 and red to terminal 6, I have achieved partial success in that I have now got it correctly making/breaking line connection when the handset is lifted/replaced, and the keypad works as expected (it is MF dial, as I assumed). In addition, the handset works perfectly on both receive and transmit.

However, I cannot get it to ring! I'm unsure as to whether this is just further tinkering required, or just general failure of the ringer/electronics itself. I've tried turning the volume/pitch controls on the bottom of the unit but they don't seem to do anything.

Given the suggestion of terminal 9 being the bell wire, I've left the blue line cord wire connected to that for the moment, with green at 8.

Any further suggestions would be gratefully received!

Thanks for the advice so far,

Nathan.

[TonyDuell]

So which are the line terminals? 6 and 7?

I assume you have an external ringing capacitor (either in a master socket or ADSL filter)

Silly suggestion : Try swapping the line wires over. Since the ringing capacitor goes from one line wire to the bell shunt wire (and the bell in the telephone from the bell shunt wire to the other line wire) it does matter which way round they are connected.

[AndiiT]

Hi,
Whilst this might not work, it wouldn't hurt to try wiring as a "two - wire" instrument so try this -

White of your line cord to terminal 2
Red of your line cord to terminal 3

Link terminals 2 and 5 and insulate the Blue and green leads of your line cord.

Using this method relies on the capacitor in the phone to ring operate the bell and not the one in the line jack/ADSL filter.

Many phones which were not intended to be used on the UK system had the internal bell capacitor in the 'A' leg of the circuit and not the 'B' leg as is required with the UK system.

Regards

Andrew

[snathe1978]

Originally Posted by TonyDuell

So which are the line terminals? 6 and 7?

Yep, it looks like 6 and 7 are line in this case.

Originally Posted by TonyDuell

I assume you have an external ringing capacitor (either in a master socket or ADSL filter)

Yes, I'm connecting the phone directly to my main and only BT socket (it's a PlusNet line but they're basically rebadged BT so there shouldn't be any oddness going on there)

Originally Posted by TonyDuell

Silly suggestion : Try swapping the line wires over. Since the ringing capacitor goes from one line wire to the bell shunt wire (and the bell in the telephone from the bell shunt wire to the other line wire) it does matter which way round they are connected.

That's something I tried in my initial tinkering and it seems that in this case it does indeed matter which way they are connected; there was no dial tone at all when white was connected to 6 and red to 7.

I may well try all this again tomorrow just in case there's something I've missed, but it looks like this may be a failure of the electronics
(which'd be a shame, as it's actually a really nice phone and I was hoping to use it as my "daily dialler", if you will!)

Thanks for the suggestions.

Nathan.

[snathe1978]

Originally Posted by AndiiT

...
White of your line cord to terminal 2
Red of your line cord to terminal 3

Link terminals 2 and 5 and insulate the Blue and green leads of your line cord.

Using this method relies on the capacitor in the phone to ring operate the bell and not the one in the line jack/ADSL filter.

Many phones which were not intended to be used on the UK system had the internal bell capacitor in the 'A' leg of the circuit and not the 'B' leg as is required with the UK system.
...

I'll try giving this method another go tomorrow; I know this is also the method listed in Bob's Telephone file however I didn't try insulating the green and blue wires so that may prove worthwhile.

(It does however look like it was always intended to be used on the UK system, given what looks like the original BABT and green circle labels)

Thanks!

[dagskarlsen]

This is a tricky one, and the ringing current (or voltage) may damage something if put in on the wrong place, so be careful. You have the rest working so do not do anything before you are sure.

Again, I have to guess, but now guessing wrong may kill the something.

If the 2 diodes in the ring of the picture are zener diodes, thay are probably there for stopping "tinkle" when a rotary is dialed on the same line. Then this wire (9) are probably one of the ringer wires.

If so we may carefully test by using a 9V (smoke detector) battery, hooksw. pressed. One pole of the battery to the pint of green arrow, the second on the different terminals 4-8, if you get any noise you probably has the terminal to apply ringing current. Bell wire to one of them, and strap between the other and the common wire.

The 2 yellow lines is where I guess the zeners are.

[TonyDuell]

How easy is it to get the keypad out of the way and see what the ICs are. My guess is that the rearmost one is the 'hybrid' (replaces the induction coil of older telephones), the one in front of it is the DTMF dialer and the little 8 pin one towards the front is the ringer.

The ringer IC might well be a standard part (actually all 3 probably are standard parts) and we can get a data sheet on it. Tracing out the ringer circuitry given the data sheet (it will follow the example circuit quite closely in my experience) is a quick job. Then we can see how it is connected to the line/terminals.

I don't see anything that could be a ringer capacitor on that board

Now, you mention it was oriignally a Special Range telephone. The original Special Range with numbers in the 1000s were connected to a 5-contact jack plug (Plug 505) and the ringers of multiple phones would end up in series. Later ones, with 8000 series numbers originally had the Plug 431A (modern line plug) and were designed to have ringers in parallel as you would expect. Often there were significant differences between the 2 types for indentical-looking telephones (I have a 'Dawn' that is the later version, looking at it I think I can work out how the older one would have been wired, but it's not obvious). Do you know this is a TSR8003? One clues is if it has REN=1 (or similar) on it, the concept of REN came in with the Plug 431A.

[snathe1978]

Originally Posted by TonyDuell

How easy is it to get the keypad out of the way and see what the ICs are. My guess is that the rearmost one is the 'hybrid' (replaces the induction coil of older telephones), the one in front of it is the DTMF dialler and the little 8 pin one towards the front is the ringer.

It should be easy enough to do, the keypad is just secured with a ribbon cable at the bottom so I should be able to move it and get a pic of the PCB underneath (although it'll probably be a day or so now thanks to real life getting in the way!)

Now, you mention it was originally a Special Range telephone. The original Special Range with numbers in the 1000s were connected to a 5-contact jack plug (Plug 505) and the ringers of multiple phones would end up in series. Later ones, with 8000 series numbers originally had the Plug 431A (modern line plug) and were designed to have ringers in parallel as you would expect. Often there were significant differences between the 2 types for identical-looking telephones (I have a 'Dawn' that is the later version, looking at it I think I can work out how the older one would have been wired, but it's not obvious). Do you know this is a TSR8003? One clues is if it has REN=1 (or similar) on it, the concept of REN came in with the Plug 431A.

I don't actually know for definite that it's a TSR8003; it's speculation on my part given the green circle approval sticker, BABT sticker and the manufacturer date of 1987, so I may well actually be wide of the mark here (although would it be safe to say that the PST system with a plug 431A would have been more commonplace at that time?)

There's no mention of a REN number as far as I can see.

Thanks for the info so far!

[snathe1978]

Originally Posted by dagskarlsen

...If so we may carefully test by using a 9V (smoke detector) battery, hooksw. pressed. One pole of the battery to the pint of green arrow, the second on the different terminals 4-8, if you get any noise you probably has the terminal to apply ringing current. Bell wire to one of them, and strap between the other and the common wire...

Thanks dagskarlsen, I'll give this a try. Will it matter about the polarity of the battery connection or not?

Appreciate all the help so far

[Nickthedentist]

Originally Posted by TonyDuell

How easy is it to get the keypad out of the way and see what the ICs are. My guess is that the rearmost one is the 'hybrid' (replaces the induction coil of older telephones), the one in front of it is the DTMF dialer and the little 8 pin one towards the front is the ringer.

The ringer IC might well be a standard part (actually all 3 probably are standard parts) and we can get a data sheet on it. Tracing out the ringer circuitry given the data sheet (it will follow the example circuit quite closely in my experience) is a quick job. Then we can see how it is connected to the line/terminals.

I was thinking the same. The Statesman (IXT) of the same era used a Texas 8-pin DIL IC for the ringer ISTR.

[dagskarlsen]

Originally Posted by snathe1978

Thanks dagskarlsen, I'll give this a try. Will it matter about the polarity of the battery connection or not?

Appreciate all the help so far

If I am right, it should not depend on polarity.

[mickash]

Nathan,

Did you get this sorted? I have a version of this phone with DTMF keypad and bell ringer. Not sure of the type number, it's dated as 1988. Mine is wired as follows, starting at the top terminal -
Blue
Vacant
Red
White
Green
See the photo below which shows how my phone is wired.

Cheers, Michael.

[dagskarlsen]

Almost equal, so I would go for the same connections.

dsk

[TonyDuell]

The difference (ringing in that last photo) seems to be a jumper wire. Looking back at the track side photos earlier, one end of that jumper seems to go to the terminal for the blue wire (bell shunt wire), the other end goes off towards the ringer IC. If it doesn't work without it, it would be worth putting that jumper in to see what happens.