Audioline Tel3 two-part phone fault - UK Vintage Radio Repair and Restoration Discussion Forum

dazzlevision · 6th Jan 2022, 5:30 pm

After 30+ years of faithful service, my Audioline Tel3 two-part phone has failed: (https://www.britishtelephones.com/audiolin/tel3.htm).

Initially, it wouldn’t ring on incoming calls and when the handset was picked up, there was no dial tone. I found that the BT 431A plug end crimped wire terminations were intermittently high resistance, so I replaced the plug and cord with a spare BT extension lead, with the female end cut off and the individual wires (only three used) soldered onto the phone’s base unit PCB.

However, although the phone now rang on incoming calls and the transmitter generated outgoing speech, there was total silence from the receiver.
I unsoldered one of the two wires to the receiver and used my Fluke 77 to measure the dc resistance of it, which was initially in the MegOhms. However, when tapping the receiver, the resistance reduced into the hundreds of Ohms – but still no sound when reconnected. I’ve also connected it to my AF signal generator, but with no discernible output.

The receiver has DR-904 embossed on it, which after Googling, seems to be an Hosiden part, with a dc resistance of around 150 Ohms. I’m assuming this is a moving coil type of transducer. It’s driven directly by an IC.

I’ve not been able to locate a replacement part, but wondered if anyone could suggest a source or an equivalent part that I could use?

dazzlevision · 6th Jan 2022, 5:35 pm

Here are some photos.

I've not been able to locate any data on the two DIL ICs fitted onto the larger PCB.

G6Tanuki · 6th Jan 2022, 6:32 pm

I've got one of those Hosiden 904 earpieces here, came out of a BT "Relate 300" I disassembled some years back.

Free of charge. PM me!

dazzlevision · 6th Jan 2022, 9:38 pm

Quote:

Originally Posted by G6Tanuki

I've got one of those Hosiden 904 earpieces here, came out of a BT "Relate 300" I disassembled some years back.

Free of charge. PM me!

PM sent!

6th Jan 2022, 5:30 pm	#1
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,608	Audioline Tel3 two-part phone fault After 30+ years of faithful service, my Audioline Tel3 two-part phone has failed: (https://www.britishtelephones.com/audiolin/tel3.htm). Initially, it wouldn’t ring on incoming calls and when the handset was picked up, there was no dial tone. I found that the BT 431A plug end crimped wire terminations were intermittently high resistance, so I replaced the plug and cord with a spare BT extension lead, with the female end cut off and the individual wires (only three used) soldered onto the phone’s base unit PCB. However, although the phone now rang on incoming calls and the transmitter generated outgoing speech, there was total silence from the receiver. I unsoldered one of the two wires to the receiver and used my Fluke 77 to measure the dc resistance of it, which was initially in the MegOhms. However, when tapping the receiver, the resistance reduced into the hundreds of Ohms – but still no sound when reconnected. I’ve also connected it to my AF signal generator, but with no discernible output. The receiver has DR-904 embossed on it, which after Googling, seems to be an Hosiden part, with a dc resistance of around 150 Ohms. I’m assuming this is a moving coil type of transducer. It’s driven directly by an IC. I’ve not been able to locate a replacement part, but wondered if anyone could suggest a source or an equivalent part that I could use?

6th Jan 2022, 5:35 pm	#2
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,608	Re: Audioline Tel3 two-part phone fault Here are some photos. I've not been able to locate any data on the two DIL ICs fitted onto the larger PCB. Attached Thumbnails

6th Jan 2022, 6:32 pm	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	Re: Audioline Tel3 two-part phone fault I've got one of those Hosiden 904 earpieces here, came out of a BT "Relate 300" I disassembled some years back. Free of charge. PM me! Attached Thumbnails __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.