Bush DAC 10 - loudspeaker problems.

[Cerberos]

I am working on a DAC 10 which is coming back to life with little effort. So far I have changed afew waxies in the audio stages and the mains input filter cap and the thiing has sprung back to life. A good clean of the switches and it is very sensative.

At this point I thought about leaving the everything else alone and putting it back together. So I picked up the speaker which was laying face down on the bench (OK for bench read kitchen worktop, it's too cold to go out in the garage) As soon as the speaker was vertical it stopped working.

Of course the first thought is that I had shorted something out, but no. Hold the speaker horizontal, it works, Put it in its normal operating position and it cuts out.

Much cleaning out with dust air followed, prodding the back of the cone with a cotton bud and finally I can get life out of the speaker in all postions.

It sounds fine at low volume but increase the volume and the speaker coils are obviously fouling the magnet.

So finally a question. Has anyone any idea how to fix a DAC 10 speaker. I am thinking like other celestion speakers of the time the bellows arrangement that fits on the back of the cone where it meets the magnet has come unglued. I can't see any way of dismantling the speaker to fix it. Unless of course someone knows better.

What do the two screws on the front of the speaker do? I am very wary of undoing them. The speaker is such a unique design I suspect I will never get a replacement if I damage it by pulling it apart.

[Nickthedentist]

John (Radiogammon) suggested a replacement speaker:

If anyone is looking for a new replacement speaker for a DAC10 or DAC90A, and indeed any other sets requiring a slimline speaker, I could recommend a Visaton model FR12 obtainable from RS (part no. 364-3290). It is a 5in, 3ohm inverted cone speaker with an overall depth of only about 1.2in and costs about £8. I recently replaced the failing speakers in the above sets with one of these and they both sound good. It was necessary to cut round baffles from thin plywood using the original speakers as templates with a 110mm diam cutout in the centre for the new speaker. This was easily achieved using a powered jigsaw and the finished baffles were sprayed matt black using an aerosol.


And Mick (Mickjjo) suggested this:


Having just read the latest issue of "Radio Bygones" and Tony Thompsons' fine article about the restoration of the DAC10, I was reminded by the current discussions on Philips "Disc Jockey" record players elsewhere on this forum, that the loudspeaker fitted in the lid of the "Disc Jockey Major" is of the same "inside out" construction as the one in the DAC10. I found that these speakers are interchangeable, and since there seem to be plenty of tatty "Disc Jockey Majors" about, I hope this is a useful tip to share.


These replies imply that the original speakers may be very difficult to repair successfully.

Nick.

[Tim]

Hello Cerebos.
Nice to see you back on the forum.
I had similar trouble with one of these speakers, and found it lessened when the front plate was clamped tightly to the main frame.
Try some 4 BA screws and nuts in the four holes not used for mounting.
I used countersink screws(with the heads on the non set side of the speaker), so tightening the mounting screws would not crack the Bakelite.

[stevekendal]

The speaker in my DAC 10 was virtually silent, seemed to have lost all of its magnetism somehow. I replaced it with a slimline one from cpc. It sounds much better than the original in my sister,s radio. Steve

[Cerberos]

As a temporary fix I have put some cotton wool in the back of the speaker between the cone and the frame just at one side.

This just pushes the cone back into the right position. I can turn it up quilte loud without distorting or fouling the magnet.

I don't consider it a permenant fix. In the long run I will have to buy a new slimline speaker.

It's back together now. Looks lovely, the bakelite has a really deep shine, the white bakelite has come up a nice ivory colour. It even has the bush logo intact on the front.

It gives me time now to find that speaker.

Time to put in an order to RS. I have a Ultra Coronation Twin that needs dropper resistors, new stock of high voltage Caps, more link up wire, scale lamp bulbs, tin of brasso............

And I thought this would be a cheap hobby.

[Cerberos]

Visaton model FR12 obtainable from RS (part no. 364-3290).

I fitted the Rs speaker as suggested. As you can see from the image it is quite a bit smaller. What the picture doesn't show is that it is also a litter slimmer.

I made an adaptor from 6mm MDF. The new speaker is mounted using counter sunk machine screws from the front side of the MDF ring.

To stop the MDF frame rattling against the case I covered the whole front of the ring in thin black foam, and mounted the ring using the original speaker mounting screws.

The foam I used is 2 or 3 mm thick and sold at Hobbycraft super stores as Fab Foam. See http://www.hobbycraft.co.uk/ideas_library/idea_77.html

The new speaker sounds very good, so good in fact I have had to fit some extra superssion to stop my PC interfereing with the radio. I have fitted a couple of high voltage disc ceramic caps in paralell with the HT smoothing Cs to cut out the high pitched whistle when the PC is on.

[Nickthedentist]

It's also available from CPC as part number LS01896 @ £6.74 + VAT