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Old 30th Jul 2019, 8:47 pm   #1
Peakoverload
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Default Bush DAC90A Speaker Question

Every time I google the Bush DAC90A it always brings up numerous threads on this forum so I'm hoping I've come to the right place.

Long story short, my grandfather had one of these and I have very fond memories of sitting with him whilst he listened to his favourite radio programmes and purely for nostalgia reasons and to have some kind of connection again to him, I'd like to try and use one of these in a project I have in mind.

Unfortunately I am not skilled in electronics and could never attempt to restore one of these, or indeed any radio, in the skilled ways you guys do. I would however, and I do hope that this isn't considered sacrilegious, love to convert one of these into a computer controlled media centre. I have already done most of the 'computer' side of things by using a Raspberry Pi and connected it up to an amplifier and I can see that you can easily pick up a DAC90A on various auction sites quite cheaply.

The bit that I can't quite work out is in regards to the speaker as none of the internal photos and restoration videos I've seen, appear to answer this.

I would like to replace the original speaker (sorry) with a new one but I can't find anything about what size the original is or see how it is mounted inside the case. I did see one page somewhere (now can't find the link) where it stated the speaker was 6" in diameter but I can't tell how it is mounted and can't work out whether I would need to find one of roughly the same size or whether I could use a smaller 4" driver. Can anyone shed any light?
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Old 30th Jul 2019, 9:01 pm   #2
AC/HL
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Default Re: Bush DAC90A Speaker Question

Hello and welcome. As you intimate, this is not our usual fare but these radios are very common so nothing irreplaceable will be lost. You may have come across this thread: https://www.vintage-radio.net/forum/...d.php?p=999519, so it is doable.
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Old 30th Jul 2019, 9:06 pm   #3
Mike. Watterson
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Default Re: Bush DAC90A Speaker Question

So really you just need an empty DAC90a case.

I don't think they are cheap, which is why I don't have one. Most 1950s radios are cheaper.

You can ALWAYS use a smaller speaker by mounting it on plywood / MDF / chipboard and mounting that on the original location.
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Old 30th Jul 2019, 10:14 pm   #4
Half a Mullard
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Default Re: Bush DAC90A Speaker Question

Hi and welcome

Yes you are right, the Forum is mainly aimed at restoring radios (and many other vintage items) in their original form. However with a DAC90A there might be a solution which could be reversed if you or anyone else wanted to put it back in original state. The main workings of the radio (the chassis) can be easily removed on these sets. Keep it safe. This would just leave the speaker in place and the dial glass (tuning scale) with the stations marked on it. If you wanted to do this we can advise on how to remove the chassis.

The speaker on these sets is low powered and fragile by modern standards and I would suggest removing it but storing it safely. Use a modern speaker Ė as mentioned a 4 inch or 5 inch should do. Iím not sure how it would sound in the empty Bakelite case, donít expect hi fi. The original speaker is screwed into the case with small self tapping screws. It might be better to make up some kind of wooden baffle as has been suggested. There are holes where the existing knobs are, again if you can avoid drilling the case it could at least be restored to original later.

Finally as you probably know these radios are connected directly to the mains and high voltages are involved. It would be best to avoid the temptation to plug it in!
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Old 31st Jul 2019, 8:49 am   #5
'LIVEWIRE?'
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Default Re: Bush DAC90A Speaker Question

May I point out an error, Howard. The speaker in a Bush DAC90A - a Celestion 6.5" Diameter one, b.t.w., is not held in by self-tapping screws, but by four angle brackets fixed to the case with short 4BA Threaded screws - a method copied much later of course by Far Eastern Radio manufacturuers.
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Old 31st Jul 2019, 9:06 am   #6
David G4EBT
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Default Re: Bush DAC90A Speaker Question

Here's how the speaker is held in place with four brackets.

The picture was annotated to show the screw threads for securing the chassis to the cabinet, and to fix the back panel, but the speaker mounting brackets which clamp the speaker in place can be seen. If a smaller speaker is preferred, then as has been said, you'd need to make a mounting board from thin plywood, MDF etc.

Hope that helps a bit.
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Old 31st Jul 2019, 9:37 am   #7
Half a Mullard
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Default Re: Bush DAC90A Speaker Question

Thanks folks, you are of course correct re the speaker fixing, been a while since I dismantled one, that's my excuse!
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Old 31st Jul 2019, 11:53 am   #8
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Default Re: Bush DAC90A Speaker Question

Please do save any bits you remove from the set. Someone here would willingly give them a good home.

Good luck,

Nick.
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Old 31st Jul 2019, 2:06 pm   #9
ThePillenwerfer
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Default Re: Bush DAC90A Speaker Question

Obvious question: Why do you want to replace the speaker? Old ones tend to be better quality than modern reasonably-priced ones and have an impedance around 4Ω which suits modern amplifier chips.

Of course it's yours to do with as you will but I'd certainly at least try the original before forking-out for a new one.
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Old 31st Jul 2019, 10:13 pm   #10
Peakoverload
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Default Re: Bush DAC90A Speaker Question

Thanks all for your replies and for your understanding. I really would love to be able to restore one of these authentically but, although I did study electronics that was 30 years ago and quite frankly I've forgotten most of it. Thanks too to David for the photo of the speaker mounting, that is very useful. In a couple of videos I'd seen, it looked like the speaker was attached to the metal chassis as it all seemed to come out as one unit.

I am actually very keen to try and preserve as much, if not all the original, parts as I'm very much into preservation and I think I might be able to fit the new equipment in around the original.

The main reason for replacing the original speaker was for a variety of reasons. I had assumed that either it wouldn't work or if it did it wouldn't sound very good and on that basis would expect that in 60+ years speaker technology would have moved on and a new one would sound better. The other reason is that I'm trying to work out how to fit a microphone in it because I've set it all up to be voice activated. With a smaller speaker I'd then have room to mount a mic behind the grill.

This is all very much "in theory" until my DAC90A turns up, hopefully on Friday, and I see things in the flesh and then it will probably all change and I'll want to restore it properly
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Old 1st Aug 2019, 6:39 am   #11
ColinB
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Default Re: Bush DAC90A Speaker Question

Quote:
Originally Posted by Peakoverload View Post
...until my DAC90A turns up, hopefully on Friday, and I see things in the flesh and then it will probably all change and I'll want to restore it properly
That's the spirit

I'm sure there must be someone local to you who could talk you through the electronic side, or do it for you?

That way you'd have a working radio rather than just a speaker in a box. Don't forget, used with a small AM transmitter, the media player idea is still very feasible.

Either way, good luck with the project.
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Old 1st Aug 2019, 9:13 am   #12
MurphyNut
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Default Re: Bush DAC90A Speaker Question

Quote:
Originally Posted by Peakoverload View Post
This is all very much "in theory" until my DAC90A turns up, hopefully on Friday, and I see things in the flesh and then it will probably all change and I'll want to restore it properly
One of my first radio restorations was a DAC90A and I've never had any electrical training, it's not as daunting as you might think, these aren't complex radios.
You'll find plenty of help here and if like me and need to be shown, youtube can be extremely helpful.
Whatever way you go, best of luck!
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Old 1st Aug 2019, 9:31 am   #13
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Default Re: Bush DAC90A Speaker Question

Quote:
Originally Posted by Peakoverload View Post
...... love to convert one of these into a computer controlled media centre. I have already done most of the 'computer' side of things by using a Raspberry Pi and connected it up to an amplifier ......
Since you have the kind of brain that is able to sort out this kind of thing you should have no problem learning how to restore a DAC90A. You'll need a couple of basic bits of kit (eg, meter and soldering iron) but nothing too expensive if you don't already have them. Could be very satisfying and lead to a life long interest (addiction?).

Best of luck whichever way you go.

Alan
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Old 1st Aug 2019, 5:23 pm   #14
HamishBoxer
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Default Re: Bush DAC90A Speaker Question

The original speaker normally sounds just fine.I have one or a few of this model and have restored many.

Apart from care needed with a "Live" chassis,these are normally a quick and easy overhaul.
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Old 1st Aug 2019, 8:56 pm   #15
Radio tirana
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Default Re: Bush DAC90A Speaker Question

Here are some pictures of a dac90A I fitted with a car type 4ohm speaker as the original one had failed. It is possible to retain the valve radio chassis and add a bluetooth module. The existing wavechange switch needs to be changed for a three position one and some alterations to the wiring to connect the audio amplifier stage to the module are necessary. I did have to space the speaker away from the front grill to prevent the rubber roll surround from fouling it. I also ended up spray painting the chrome tweeter black so that you could not see it through the mesh.
I have both modified and original versions of this iconic set and enjoy them both, you will find a wealth of advice and practical advice on this forum if you do decide to restore your radio. Many of us started with a 90a.

Kind regards RT
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