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

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?

6th Jan 2022, 5:30 pm	#1
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,612	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?