Murphy A122 is heavy smoker... - UK Vintage Radio Repair and Restoration Discussion Forum

PJL · 10th Mar 2007, 11:26 pm

Cleaned the switches, replaced the audio coupling capacitor and checked the HT and output valve cathode current but after a few minutes a smoke cloud appeared from the screen/HT dropper.

Refering to trader sheet 962. I couldn't work out what could be taking the current and eventually traced it to the waveband switch which was breaking down from switch 18 to the aluminium spacer. A clean and mica washer fixed it.

A good example of why it is not wise to leave valve radios unattended.

radiohm · 11th Mar 2007, 12:19 am

Could have been nasty. A lesson to us all not to get complacent with our equipment.

Regards.

Mike.

paulsherwin · 11th Mar 2007, 2:04 am

Waveband switch faults aren't that uncommon. especially with vhf sets.

It's certainly a good idea not to leave sets unattended until thy've had time to prove themselves

Paul

Simon Gittins · 11th Mar 2007, 10:44 am

I have an A122 on the bench at the moment, basically working after changing the audio coupling capacitor and HL41DD.

I shall certainly check the waveband switch!

As mentioned on Paul's main site, the rubber wiring tends to deteriorate on this set; mine will be using up some of the silicone-rubber wire I bought at Harpenden.

10th Mar 2007, 11:26 pm	#1
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Murphy A122 is heavy smoker... Cleaned the switches, replaced the audio coupling capacitor and checked the HT and output valve cathode current but after a few minutes a smoke cloud appeared from the screen/HT dropper. Refering to trader sheet 962. I couldn't work out what could be taking the current and eventually traced it to the waveband switch which was breaking down from switch 18 to the aluminium spacer. A clean and mica washer fixed it. A good example of why it is not wise to leave valve radios unattended.

11th Mar 2007, 12:19 am	#2
radiohm Pentode Join Date: Jan 2006 Location: Stockton On Tees, Cleveland Posts: 18	Re: Murphy A122 is heavy smoker... Could have been nasty. A lesson to us all not to get complacent with our equipment. Regards. Mike.

11th Mar 2007, 2:04 am	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: Murphy A122 is heavy smoker... Waveband switch faults aren't that uncommon. especially with vhf sets. It's certainly a good idea not to leave sets unattended until thy've had time to prove themselves Paul

11th Mar 2007, 10:44 am	#4
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 506	Re: Murphy A122 is heavy smoker... I have an A122 on the bench at the moment, basically working after changing the audio coupling capacitor and HL41DD. I shall certainly check the waveband switch! As mentioned on Paul's main site, the rubber wiring tends to deteriorate on this set; mine will be using up some of the silicone-rubber wire I bought at Harpenden.