Bush AC41 speaker arrangement - UK Vintage Radio Repair and Restoration Discussion Forum

Gordonc · 20th Mar 2012, 12:27 am

Hi all,
I am attempting my first restoration of a Bush AC41. All is going ok so far. I have replaced all of the wax caps, but I am a bit unsure of the speaker arrangement. The back panel shows "External loudspeaker" and " Internal loudspeaker switch - unscrew to disconnect". I am puzzled as a) this is not really a switch, just a large handscrew, and b) there is nothing connected to this screw! When I power up the set, I get zilch from the internal speaker. What should I be doing?

Darren-UK · 20th Mar 2012, 12:48 am

I'm rather puzzled by this as I thought all the AC41 had on its rear was four sockets; aerial+earth and two for 'gram'?

Anyway, whatever, all that screw will do is push apart/allow to connect a pair of contacts in the 'speaker wiring. The action is similar to when you insert an earphone jack into the socket provided on some transistor radios and it cuts out the internal 'speaker.

Check the output transformer secondary to make sure the set is indeed babbling away and, if it is, suspect those contacts mentioned above. Don't run the radio, assuming it is working, with no 'speaker connected for long though.

Gordonc · 20th Mar 2012, 9:20 am

Hi Darren,
Thanks for the quick reply. Having looked again at the service sheet, (Bush AC/DAC41) it appears that there are definitely connections for an external speaker, shown on the AC41 circuit diagram as S8 and SK1/A and SK1/B, S8 being the Screw, and the SKs (I assume) being the input sockets.

Station X · 20th Mar 2012, 10:02 am

S8 disconnects the internal speaker. You'll have to inspect it to check whether the screw needs to be in or out to enable the speaker. You may need to clean or adjust the contacts too.

SK1A and SK1B are the OUTPUT sockets for connection to an external speaker.

Gordonc · 20th Mar 2012, 10:45 am

Thanks Graham.
I will check it as you say and see if I get anything through the internal speaker.

Thanks again for your help.

Gordon.

Gordonc · 21st Mar 2012, 12:06 am

Hi! Me again I'm afraid. I checked the screw fitting as Graham advised but it does not appear to have contact with anything! The wiring is as follows:
One wire runs from SK1/B to the transformer and continues to one terminal on the internal speaker. A second wire runs from SK1/A to the transformer. A third wire is connected directly to the remaining terminal on the speaker, from a brass plate/bracket through which the screw runs. I have a feeling that an additional wire or connection may be missing. Any thoughts would be appreciated.

Thanks,

Gordon.

Steve_P · 21st Mar 2012, 12:18 am

Get two lengths of wire and go from the secondary of the output transformer to the speaker. Try that. If it works you have a wiring problem. Easy to sort or just put the two new wires in neatly.

If it stays obstinately silent, come back.

Cheers,

Steve P.

Station X · 21st Mar 2012, 12:41 am

Looks like there should be an additional wire from SK1A, or the transformer terminal it connects to, to a second terminal near the screw. It's possible the screw itself is a conductor.

For testing purposes, just run a wire from SK1A to the brass plate, or the speaker terminal it's connected to.

Gordonc · 21st Mar 2012, 12:48 am

Thanks guys. I will try both methods and let you know the result.

Cheers,

Gordon.

paulsherwin · 21st Mar 2012, 1:18 am

This arrangement was quite common. Radios cost an awful lot then, and many people wired an extension speaker in the kitchen or dining room connected to the main radio in the living room. The screw disconnected the internal speaker, which allowed both silence in the living room and better transformer matching for the extension speaker.

The output transformer just has a 3 ohm output for a speaker. If you never need to use an extension speaker, you could just wire it directly to the internal speaker ignoring the screw and LS sockets.

Don't use the radio without any speaker connected, as this will cause very high AC voltages in the output transformer primary which may result in damage.

Gordonc · 21st Mar 2012, 12:04 pm

Hi guys,
Have got some life in the speaker now!
However as you have probably guessed, I am new to the Bush AC41, so I assume as it has no frame aerial that I will need to plug in an external wire/aerial to be able to get decent reception yes? Do I also need to connect an earth wire to the earth socket?

Gordon.

Steve_P · 21st Mar 2012, 3:12 pm

Aerial and earth will make a drastic improvement to the set. You may be able to get away with an aerial, a long wire will do.

As far as an earth is concerned, a water pipe will do. NOT GAS...

Cheers,

Steve P.

Gordonc · 21st Mar 2012, 6:10 pm

Radio is now working fine and reception is excellent! Thanks for all of your help guys - greatly appreciated!

One very minor problemette - no wanda plugs to attach the aerial and earth wires to! Anyone know where these can be obtained as I like to maintain the radio's authenticity so don't really want to put modern banana sockets on it.

Gordon.

Steve_P · 21st Mar 2012, 8:02 pm

Well, try here for ideas..

https://www.vintage-radio.net/forum/...ead.php?t=7247

Cheers,

Steve P.

Audio1950 · 22nd Mar 2012, 12:05 am

Quote:

Originally Posted by Gordonc

Anyone know where these can be obtained as I like to maintain the radio's authenticity so don't really want to put modern banana sockets on it.Gordon.

Gordon, if you still need wander plugs, send me a pm with name and address, and I'll get a couple in the post. Red or black?

Barry

20th Mar 2012, 12:27 am	#1
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Bush AC41 speaker arrangement Hi all, I am attempting my first restoration of a Bush AC41. All is going ok so far. I have replaced all of the wax caps, but I am a bit unsure of the speaker arrangement. The back panel shows "External loudspeaker" and " Internal loudspeaker switch - unscrew to disconnect". I am puzzled as a) this is not really a switch, just a large handscrew, and b) there is nothing connected to this screw! When I power up the set, I get zilch from the internal speaker. What should I be doing? __________________ Gordonc

20th Mar 2012, 12:48 am	#2
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: Bush AC41 speaker arrangement I'm rather puzzled by this as I thought all the AC41 had on its rear was four sockets; aerial+earth and two for 'gram'? Anyway, whatever, all that screw will do is push apart/allow to connect a pair of contacts in the 'speaker wiring. The action is similar to when you insert an earphone jack into the socket provided on some transistor radios and it cuts out the internal 'speaker. Check the output transformer secondary to make sure the set is indeed babbling away and, if it is, suspect those contacts mentioned above. Don't run the radio, assuming it is working, with no 'speaker connected for long though.

20th Mar 2012, 9:20 am	#3
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Hi Darren, Thanks for the quick reply. Having looked again at the service sheet, (Bush AC/DAC41) it appears that there are definitely connections for an external speaker, shown on the AC41 circuit diagram as S8 and SK1/A and SK1/B, S8 being the Screw, and the SKs (I assume) being the input sockets. __________________ Gordonc

20th Mar 2012, 10:02 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush AC41 speaker arrangement S8 disconnects the internal speaker. You'll have to inspect it to check whether the screw needs to be in or out to enable the speaker. You may need to clean or adjust the contacts too. SK1A and SK1B are the OUTPUT sockets for connection to an external speaker. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

20th Mar 2012, 10:45 am	#5
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Thanks Graham. I will check it as you say and see if I get anything through the internal speaker. Thanks again for your help. Gordon. __________________ Gordonc

21st Mar 2012, 12:06 am	#6
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Hi! Me again I'm afraid. I checked the screw fitting as Graham advised but it does not appear to have contact with anything! The wiring is as follows: One wire runs from SK1/B to the transformer and continues to one terminal on the internal speaker. A second wire runs from SK1/A to the transformer. A third wire is connected directly to the remaining terminal on the speaker, from a brass plate/bracket through which the screw runs. I have a feeling that an additional wire or connection may be missing. Any thoughts would be appreciated. Thanks, Gordon. __________________ Gordonc

21st Mar 2012, 12:18 am	#7
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush AC41 speaker arrangement Get two lengths of wire and go from the secondary of the output transformer to the speaker. Try that. If it works you have a wiring problem. Easy to sort or just put the two new wires in neatly. If it stays obstinately silent, come back. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

21st Mar 2012, 12:41 am	#8
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush AC41 speaker arrangement Looks like there should be an additional wire from SK1A, or the transformer terminal it connects to, to a second terminal near the screw. It's possible the screw itself is a conductor. For testing purposes, just run a wire from SK1A to the brass plate, or the speaker terminal it's connected to. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Mar 2012, 12:48 am	#9
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Thanks guys. I will try both methods and let you know the result. Cheers, Gordon. __________________ Gordonc

21st Mar 2012, 1:18 am	#10
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: Bush AC41 speaker arrangement This arrangement was quite common. Radios cost an awful lot then, and many people wired an extension speaker in the kitchen or dining room connected to the main radio in the living room. The screw disconnected the internal speaker, which allowed both silence in the living room and better transformer matching for the extension speaker. The output transformer just has a 3 ohm output for a speaker. If you never need to use an extension speaker, you could just wire it directly to the internal speaker ignoring the screw and LS sockets. Don't use the radio without any speaker connected, as this will cause very high AC voltages in the output transformer primary which may result in damage.

21st Mar 2012, 12:04 pm	#11
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Hi guys, Have got some life in the speaker now! However as you have probably guessed, I am new to the Bush AC41, so I assume as it has no frame aerial that I will need to plug in an external wire/aerial to be able to get decent reception yes? Do I also need to connect an earth wire to the earth socket? Gordon. __________________ Gordonc

21st Mar 2012, 3:12 pm	#12
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush AC41 speaker arrangement Aerial and earth will make a drastic improvement to the set. You may be able to get away with an aerial, a long wire will do. As far as an earth is concerned, a water pipe will do. NOT GAS... Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

21st Mar 2012, 6:10 pm	#13
Gordonc Pentode Join Date: Sep 2011 Location: Consett, County Durham, UK. Posts: 118	Re: Bush AC41 speaker arrangement Radio is now working fine and reception is excellent! Thanks for all of your help guys - greatly appreciated! One very minor problemette - no wanda plugs to attach the aerial and earth wires to! Anyone know where these can be obtained as I like to maintain the radio's authenticity so don't really want to put modern banana sockets on it. Gordon. __________________ Gordonc

21st Mar 2012, 8:02 pm	#14
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Bush AC41 speaker arrangement Well, try here for ideas.. https://www.vintage-radio.net/forum/...ead.php?t=7247 Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?