Murphy A104 - UK Vintage Radio Repair and Restoration Discussion Forum

robin coleman · 17th May 2017, 7:52 pm

I have recently purchased one of these sets. On the circuit of the Murphy service instructions C33 and C36 are described as 50 uf electrolitics but they appear to be waxies on the chassis in frount of me. There is no parts listing with the manual so I do not know if there was an error in the printing. Hopefully someone knows this set.

Regards Robin.

Silicon · 17th May 2017, 9:29 pm

Are you looking at the A104R service manual?

That is the Radiogram model and the component values and positions may be slightly different to the table model.

If you start tracing the circuit from the cathode connections on the valve socket you will find the two capacitors.

Station X · 17th May 2017, 10:40 pm

C33 and C36 are cathode bypass caps and are shown on the A104 diagram as polarised caps with a value of 50 (no units). Therefore they must be 50uF electrolytics. You won't find waxies with values greater than about 1uF. If replacing these use 47uF units.

robin coleman · 18th May 2017, 6:53 am

Thank you Graham they are quite large and they have lost their numbers as the wax has melted on as they are residing behind two valves.

Regards, Robin.

Station X · 18th May 2017, 8:30 am

I think you need to check that you're looking at the correct capacitors. Trace the wiring as suggested by Silicon.

17th May 2017, 7:52 pm	#1
robin coleman Hexode Join Date: Oct 2011 Location: Portsmouth, Hampshire, UK. Posts: 354	Murphy A104 I have recently purchased one of these sets. On the circuit of the Murphy service instructions C33 and C36 are described as 50 uf electrolitics but they appear to be waxies on the chassis in frount of me. There is no parts listing with the manual so I do not know if there was an error in the printing. Hopefully someone knows this set. Regards Robin.

17th May 2017, 9:29 pm	#2
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,171	Re: Murphy A104 Are you looking at the A104R service manual? That is the Radiogram model and the component values and positions may be slightly different to the table model. If you start tracing the circuit from the cathode connections on the valve socket you will find the two capacitors.

17th May 2017, 10:40 pm	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Murphy A104 C33 and C36 are cathode bypass caps and are shown on the A104 diagram as polarised caps with a value of 50 (no units). Therefore they must be 50uF electrolytics. You won't find waxies with values greater than about 1uF. If replacing these use 47uF units. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

18th May 2017, 6:53 am	#4
robin coleman Hexode Join Date: Oct 2011 Location: Portsmouth, Hampshire, UK. Posts: 354	Re: Murphy A104 Thank you Graham they are quite large and they have lost their numbers as the wax has melted on as they are residing behind two valves. Regards, Robin.

18th May 2017, 8:30 am	#5
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Murphy A104 I think you need to check that you're looking at the correct capacitors. Trace the wiring as suggested by Silicon. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.