Quiet or no dial tone in a GPO 706 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

pip5678 · 17th May 2020, 4:32 pm

Quote:

Originally Posted by Sparks

Sorry pip and Dave. This is the bit where my lack of tech savvy comes in. Whereabouts do I need to be placing my probes to look for these values and continuity ? Also, is the induction coil the thing in this picture below ? Thankyou.

Yes that's the one, I haven't got a 706 to hand but you should be able to trace the wire from T1 to the coil tag 3 (probably numbered on the coil) and if you can find tag 2 you should see the winding resistance between them which says 6Ω on the diagram. Tag 2 goes to to R1 which should be 150Ω and the other end of that goes back to T2.

So to recap put one end your ohmmeter on T1, find tag 3 on the coil, this should be 0Ω to there then go to tag 2 should be c6Ω follow the wire on tag 2 to R1 it should read the same, then go on the other side of the resistor another 150Ω in addition. Leave your second probe there on the resistor and move your first probe from T1 to T2 should be 0Ω.

Phew I hope this makes sense.

Sparks · 17th May 2020, 4:33 pm

178 ohms Wayne. I am getting this reading with the switch on OR off.

Sparks · 17th May 2020, 4:50 pm

Pip, hope I understood.

T1 to coil Tag 3 is 0.5 ohms
T1 to coil Tag 2 is 6.1 ohms
Coil Tag 2 to R1 (left hand side) is 0.5 ohms
Coil Tag 2 to R1 (right hand side) is 173 ohms
T2 to R1 (right hand side) is 0.5 ohms.

pip5678 · 17th May 2020, 5:10 pm

Quote:

Originally Posted by Sparks

Pip, hope I understood.

T1 to coil Tag 3 is 0.5 ohms
T1 to coil Tag 2 is 6.1 ohms
Coil Tag 2 to R1 (left hand side) is 0.5 ohms
Coil Tag 2 to R1 (right hand side) is 173 ohms
T2 to R1 (right hand side) is 0.5 ohms.

That sounds ok, better than we got before 'T1 to T2 is open circuit with the handset disconnected.'

I'll stand down a while as Wayne is giving some good advice and I don't want to cause confusion or duplication.

Sparks · 17th May 2020, 5:11 pm

Thanks pip.

WayneL74 · 17th May 2020, 5:27 pm

As Pip says all those readings look good.

There are 2 final parts of the ASTIC we haven't tested. Can you please test pins 1 & 2 and then 4 & 5. Do this with the switch hooks down & the regulator board removed

Sparks · 17th May 2020, 5:41 pm

Pin 1 to Pin 2 is 8.1 ohms
Pin 4 to Pin 5 is 20.3 ohms.

WayneL74 · 17th May 2020, 5:53 pm

That's good. That means the ASTIC is fine.

Can you put the regulator back in"upside down" as it were. This is so we bypass all the compnecnts on there should there be a problem.

Then can you test from T19 to T3. Should be around 22 ohms

Sparks · 17th May 2020, 6:03 pm

I'm getting nothing between T19 and T3. Whether I have the switch on or off or whichever probe is on which terminal, the display on the meter doesn't change from '1'.

TonyDuell · 17th May 2020, 6:17 pm

OK, you do have the regulator PCB fitted in its socket 'upside down'. That is with the end that connects the 3 middle contacts on the socket with a simple PCB trace in the socket.

Connect one multimeter probe to T19 and leave it there.

Put the other probe on terminal 4 of the ASTIC. Should be 0 ohms or close to it (this checks the gravity switch contact and associated wiring).

Move the probe to terminal 5 of the ASTIC. Should be 22 ohms (this checks the ASTIC winding, even though you've already done so)

Move the probe to that PCB trace on the regulator that I mentioned. Should still be 22 ohms (this checks the wiring from ASTIC pin 5 to the regualtor terminal C).

Move the probe to T3. Should stll be 22 ohms (this checks the wiring from regulator termnal B to T3).

WayneL74 · 17th May 2020, 6:26 pm

Hi Sparks.

Sounds like it could be the regulator or its wiring.

Can you just confirm it is fitted as per the attached photo?

Sparks · 17th May 2020, 7:12 pm

Wayne and Tony. I confirm the regulator is fitted upside down.

T19 to Pin 4 of the ASTIC is 0 ohms. All the other readings Tony asked for are also 0 ohms. As per my post 29, the meter doesn't change from '1' at all.

WayneL74 · 17th May 2020, 7:22 pm

Can you try from T3 to terminal B on the regulator connector - This is the 2nd one from the left.

Sparks · 17th May 2020, 7:23 pm

I have just swapped regulators with my other 706 and there was no change with either phone. The existing one is as good as ever, the newer one with its known faults.

Sparks · 17th May 2020, 7:26 pm

Wayne, 0.4 ohms.

WayneL74 · 17th May 2020, 7:30 pm

OK measure from the regulator connector C (the centre one) to pin 5 on the ASTIC

Sparks · 17th May 2020, 7:38 pm

0.4 ohms again. I'm just going to have some dinner now so I'll look in again soon. In the meantime thankyou enormously for your help.

WayneL74 · 17th May 2020, 8:00 pm

Hi Sparks.

There is something not quite rights here.

You said there was no continuity from T3 to T19, but since then we have proved there shoud be as we have tested each stage one by one.

Can you try the following with the regulator in upside down & the switchhooks up:

Hold 1 probe on T3. Hold the other probe on regulator contact B, then move it to regulator contact C, then to ASTIC pin 5, then to ASTIC pin 4, then to T19.

You should get continuity all the way, with the resistance increasing as it goes.

Sparks · 17th May 2020, 8:11 pm

I'll give that a try shortly Wayne and come back to you.

Sparks · 17th May 2020, 8:25 pm

T3 to Regulator B is 0.5 ohms with continuity
T3 to Regulator C as above
T3 to ASTIC 5 as above
T3 to ASTIC 4 is 20.2 ohms with continuity

T3 to T19 is still absolutely nothing. Apart from the straps from T19/18/17/16, the only connection from T19 is a green wire going to a (I think) capacitor.

17th May 2020, 4:33 pm	#22
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 178 ohms Wayne. I am getting this reading with the switch on OR off. Last edited by Sparks; 17th May 2020 at 4:59 pm.

17th May 2020, 4:50 pm	#23
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 Pip, hope I understood. T1 to coil Tag 3 is 0.5 ohms T1 to coil Tag 2 is 6.1 ohms Coil Tag 2 to R1 (left hand side) is 0.5 ohms Coil Tag 2 to R1 (right hand side) is 173 ohms T2 to R1 (right hand side) is 0.5 ohms.

17th May 2020, 5:11 pm	#25
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 Thanks pip.

17th May 2020, 5:27 pm	#26
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 As Pip says all those readings look good. There are 2 final parts of the ASTIC we haven't tested. Can you please test pins 1 & 2 and then 4 & 5. Do this with the switch hooks down & the regulator board removed Last edited by WayneL74; 17th May 2020 at 5:32 pm. Reason: Additional information

17th May 2020, 5:41 pm	#27
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 Pin 1 to Pin 2 is 8.1 ohms Pin 4 to Pin 5 is 20.3 ohms.

17th May 2020, 5:53 pm	#28
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 That's good. That means the ASTIC is fine. Can you put the regulator back in"upside down" as it were. This is so we bypass all the compnecnts on there should there be a problem. Then can you test from T19 to T3. Should be around 22 ohms

17th May 2020, 6:03 pm	#29
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 I'm getting nothing between T19 and T3. Whether I have the switch on or off or whichever probe is on which terminal, the display on the meter doesn't change from '1'.

17th May 2020, 6:17 pm	#30
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Quiet or no dial tone in a GPO 706 OK, you do have the regulator PCB fitted in its socket 'upside down'. That is with the end that connects the 3 middle contacts on the socket with a simple PCB trace in the socket. Connect one multimeter probe to T19 and leave it there. Put the other probe on terminal 4 of the ASTIC. Should be 0 ohms or close to it (this checks the gravity switch contact and associated wiring). Move the probe to terminal 5 of the ASTIC. Should be 22 ohms (this checks the ASTIC winding, even though you've already done so) Move the probe to that PCB trace on the regulator that I mentioned. Should still be 22 ohms (this checks the wiring from ASTIC pin 5 to the regualtor terminal C). Move the probe to T3. Should stll be 22 ohms (this checks the wiring from regulator termnal B to T3).

17th May 2020, 6:26 pm	#31
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 Hi Sparks. Sounds like it could be the regulator or its wiring. Can you just confirm it is fitted as per the attached photo? Attached Thumbnails

17th May 2020, 7:12 pm	#32
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 Wayne and Tony. I confirm the regulator is fitted upside down. T19 to Pin 4 of the ASTIC is 0 ohms. All the other readings Tony asked for are also 0 ohms. As per my post 29, the meter doesn't change from '1' at all.

17th May 2020, 7:22 pm	#33
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 Can you try from T3 to terminal B on the regulator connector - This is the 2nd one from the left.

17th May 2020, 7:23 pm	#34
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 I have just swapped regulators with my other 706 and there was no change with either phone. The existing one is as good as ever, the newer one with its known faults.

17th May 2020, 7:26 pm	#35
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 Wayne, 0.4 ohms.

17th May 2020, 7:30 pm	#36
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 OK measure from the regulator connector C (the centre one) to pin 5 on the ASTIC

17th May 2020, 7:38 pm	#37
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 0.4 ohms again. I'm just going to have some dinner now so I'll look in again soon. In the meantime thankyou enormously for your help.

17th May 2020, 8:00 pm	#38
WayneL74 Triode Join Date: Jun 2015 Location: Ipswich, Suffolk, UK. Posts: 49	Re: Quiet or no dial tone in a GPO 706 Hi Sparks. There is something not quite rights here. You said there was no continuity from T3 to T19, but since then we have proved there shoud be as we have tested each stage one by one. Can you try the following with the regulator in upside down & the switchhooks up: Hold 1 probe on T3. Hold the other probe on regulator contact B, then move it to regulator contact C, then to ASTIC pin 5, then to ASTIC pin 4, then to T19. You should get continuity all the way, with the resistance increasing as it goes.

17th May 2020, 8:11 pm	#39
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 I'll give that a try shortly Wayne and come back to you.

17th May 2020, 8:25 pm	#40
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 597	Re: Quiet or no dial tone in a GPO 706 T3 to Regulator B is 0.5 ohms with continuity T3 to Regulator C as above T3 to ASTIC 5 as above T3 to ASTIC 4 is 20.2 ohms with continuity T3 to T19 is still absolutely nothing. Apart from the straps from T19/18/17/16, the only connection from T19 is a green wire going to a (I think) capacitor.