Bush BP 81 - UK Vintage Radio Repair and Restoration Discussion Forum

Bigears · 29th Jun 2022, 2:31 pm

Hi Guys
I have a Bush BP81 it takes Ever Ready AD35 or B126 or Vidor L5512 Batteries
there are 4 wires Blue and brown and Red and black , am I right to think they are for the battery ? if so which is positive or negative. and would 9v PP9 Battery work with it

akuram1 · 29th Jun 2022, 2:57 pm

AD35 is 1.5v for filaments, B126 is 90v for HT. Need to trace out which two are HT, probably red + and black negative.
Do not use the PP9 as it will damage the filaments, they are very fragile on sets like this.

Cobaltblue · 29th Jun 2022, 4:54 pm

Quote:

Originally Posted by Bigears

Hi Guys
I have a Bush BP81 it takes Ever Ready AD35 or B126 or Vidor L5512 Batteries
there are 4 wires Blue and brown and Red and black , am I right to think they are for the battery ? if so which is positive or negative. and would 9v PP9 Battery work with it

Arkum1 is correct be careful these battery valves have in recent years become expensive and they are delicate compared to mains valves.
If you damage the valves replacements could easily make the repair unacceptably costly.

Red and Black is the HT battery 90V so can be made up of 10 times PP3 in series the red being the +ve connection

Brown and Blue are the LT connections 1.5V a D cell or a C cell are suitable.

I am pretty certain these are counter-intuitive and the blue is the +ve connection and the Brown is the negative connection.

Don't expect the valve to light up You can just about see them in a dark room if your lucky

If anyone known that the connection are wrong please speak up I don't know where my BP81 is to check.

Might pay you to check you valves have continuity on the filaments before you start.

Cheers

Mike T

ms660 · 29th Jun 2022, 5:35 pm

Quote:

Originally Posted by Cobaltblue

Brown and Blue are the LT connections 1.5V a D cell or a C cell are suitable.

I am pretty certain these are counter-intuitive and the blue is the +ve connection and the Brown is the negative connection.

Yes that's correct so far as I can make out according to an online photo and a copy of the service manual.

Lawrence

Cobaltblue · 29th Jun 2022, 6:04 pm

Thanks Lawrence must be 10 years since I worked on mine.

Cheers

Mike T

Bigears · 30th Jun 2022, 4:20 pm

Thanks Guys

29th Jun 2022, 2:31 pm	#1
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 144	Bush BP 81 Hi Guys I have a Bush BP81 it takes Ever Ready AD35 or B126 or Vidor L5512 Batteries there are 4 wires Blue and brown and Red and black , am I right to think they are for the battery ? if so which is positive or negative. and would 9v PP9 Battery work with it Attached Thumbnails

29th Jun 2022, 2:57 pm	#2
akuram1 Pentode Join Date: Sep 2009 Location: Dundee, UK. Posts: 158	Re: Bush BP 81 AD35 is 1.5v for filaments, B126 is 90v for HT. Need to trace out which two are HT, probably red + and black negative. Do not use the PP9 as it will damage the filaments, they are very fragile on sets like this.

29th Jun 2022, 6:04 pm	#5
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,874	Re: Bush BP 81 Thanks Lawrence must be 10 years since I worked on mine. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

30th Jun 2022, 4:20 pm	#6
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 144	Re: Bush BP 81 Thanks Guys