Bush DAC90A query - UK Vintage Radio Repair and Restoration Discussion Forum

Colin1949 · 13th Mar 2019, 6:33 pm

I'm trying to identify the + terminal on the speaker, green wire or, I think the other wire is mauve colour.
Than you.

Paul JD · 13th Mar 2019, 7:15 pm

I can't help with the wire colours but with the speaker disconnected you can determine the phase by briefly touching a 9v battery to the speaker terminals and observing which way the cone moves. If the cone moves outwards the terminal that the battery + is touching is the + terminal.

As it is a mono radio with a single speaker it is irrelevant which way the speaker is connected though

Ian - G4JQT · 13th Mar 2019, 8:00 pm

It doesn't matter. There is no DC going through a speaker when driven through a transformer. In fact there should never be any DC going through a loudspeaker in a conventional set up, so it never matters.

Ian

Stylo N M · 13th Mar 2019, 8:11 pm

Hi,

looking at the DAC90A radio's i have here, the original rubber covered wire colours were green and yellow. The yellow being the positive from the output sound transformer.

As Paul JD has already exsplained, it doesn't really matter wich way round the speaker is connected, it will run quite happily eather way.

I would be a bit carefull about placing a fully charged 9 volt battery directly accross the speaker terminals, as the susspension of the voice coil, could easily be damaged, due to it's age brittleness and fragility.

Paul

Paul JD · 13th Mar 2019, 8:24 pm

Quote:

Originally Posted by Ian - G4JQT

It doesn't matter. There is no DC going through a speaker when driven through a transformer. In fact there should never be any DC going through a loudspeaker in a conventional set up, so it never matters.

It matters if you have more than one speaker, either stereo or twin speaker mono. If they are out of phase you will get signal cancellation.

Quote:

Originally Posted by Stylo N M

I would be a bit carefull about placing a fully charged 9 volt battery directly accross the speaker terminals, as the susspension of the voice coil, could easily be damaged, due to it's age brittleness and fragility.

Good point, with an older small speaker such as this probably best to use a 1.5v battery.

Mike. Watterson · 13th Mar 2019, 10:28 pm

1.5V is enough for almost anything. Works even for 2000 + 2000 ohms earphones wired in series. Maybe not for Electrostatic speakers.

Colin1949 · 14th Mar 2019, 1:36 am

Thank you all for quick response. The answers. Make everything much clearer.

Ian - G4JQT · 30th Mar 2019, 12:53 pm

Quote:

Originally Posted by Paul JD

Quote:

Originally Posted by Ian - G4JQT

It doesn't matter. There is no DC going through a speaker when driven through a transformer. In fact there should never be any DC going through a loudspeaker in a conventional set up, so it never matters.

Ian

It matters if you have more than one speaker, either stereo or twin speaker mono. If they are out of phase you will get signal cancellation.

Yes, quite correct - that's when it does matter. But not for mono radios with just one speaker like the DAC90A.

13th Mar 2019, 6:33 pm	#1
Colin1949 Diode Join Date: Nov 2018 Location: Newbiggin-by-the-Sea, Northumberland, UK. Posts: 7	Bush DAC90A query I'm trying to identify the + terminal on the speaker, green wire or, I think the other wire is mauve colour. Than you.

13th Mar 2019, 7:15 pm	#2
Paul JD Pentode Join Date: Oct 2018 Location: Coventry, West Midlands, UK. Posts: 220	Re: Bush DAC90A query I can't help with the wire colours but with the speaker disconnected you can determine the phase by briefly touching a 9v battery to the speaker terminals and observing which way the cone moves. If the cone moves outwards the terminal that the battery + is touching is the + terminal. As it is a mono radio with a single speaker it is irrelevant which way the speaker is connected though

13th Mar 2019, 8:00 pm	#3
Ian - G4JQT Octode Join Date: Jun 2004 Location: Reading/Fakenham, UK. Posts: 1,323	Re: Bush DAC90A query It doesn't matter. There is no DC going through a speaker when driven through a transformer. In fact there should never be any DC going through a loudspeaker in a conventional set up, so it never matters. Ian

13th Mar 2019, 8:11 pm	#4
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Bush DAC90A query Hi, looking at the DAC90A radio's i have here, the original rubber covered wire colours were green and yellow. The yellow being the positive from the output sound transformer. As Paul JD has already exsplained, it doesn't really matter wich way round the speaker is connected, it will run quite happily eather way. I would be a bit carefull about placing a fully charged 9 volt battery directly accross the speaker terminals, as the susspension of the voice coil, could easily be damaged, due to it's age brittleness and fragility. Paul

13th Mar 2019, 10:28 pm	#6
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Bush DAC90A query 1.5V is enough for almost anything. Works even for 2000 + 2000 ohms earphones wired in series. Maybe not for Electrostatic speakers.

14th Mar 2019, 1:36 am	#7
Colin1949 Diode Join Date: Nov 2018 Location: Newbiggin-by-the-Sea, Northumberland, UK. Posts: 7	Re: Bush DAC90A query Thank you all for quick response. The answers. Make everything much clearer.