Next Year's project

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Ray P
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#31 Re: Next Year's project

Post by Ray P »

Mike H wrote: Sat Nov 24, 2018 9:10 pm I approve of your plan to try to rescue something.
Thanks Mike, trying to make something of it does feel like the right thing to do.

I've now got a schematic so I can start to make more sense of it. It does have a mains transformer. Power supply looks like a CLC arrangement after a U50 rectifier valve. You're right about the OPT, it was originally mounted on the speaker frame but when the crappy modern speaker was installed the OPT was relocated to the chassis.

I got dragged out to do some Christmas shopping after my bike ride today so little time to spend on this today but I promise to post some pictures tomorrow.
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Mike H
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#32 Re: Next Year's project

Post by Mike H »

Ray P wrote: Sat Nov 24, 2018 11:52 pm I've now got a schematic so I can start to make more sense of it. It does have a mains transformer. Power supply looks like a CLC arrangement after a U50 rectifier valve. You're right about the OPT, it was originally mounted on the speaker frame but when the crappy modern speaker was installed the OPT was relocated to the chassis.
Yep makes sense.

What is the 'L' of the CLC ? As I said before, often it is the electro field magnet of the speaker. All I'm thinking is, if the original speaker is gone, so is the choke?


I got dragged out to do some Christmas shopping after my bike ride today so little time to spend on this today but I promise to post some pictures tomorrow.
And aren't I glad that doesn't happen to me anymore. :lol:
 
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Ray P
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#33 Re: Next Year's project

Post by Ray P »

Mike H wrote: Sun Nov 25, 2018 2:01 pm What is the 'L' of the CLC ?
I think its a seperate choke based on reading the schematic but I need to trace the schematic against the actual chassis to confirm.
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Ray P
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#34 Re: Next Year's project

Post by Ray P »

The schematic is part of a service manual that includes diagrams of the chassis layout and they shows that the power supply choke is a seperate component.
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Mike H
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#35 Re: Next Year's project

Post by Mike H »

Very interesting. So speaker had a permanent magnet? Should be fairly obvious on the diagram if it had an electro.
 
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#36 Re: Next Year's project

Post by jack »

They're known as "energised" or "electrodynamic" speakers, and are mostly from the 50s.

If the speaker had more than two wires going to it, it's possible. However I don't remember the Derwent (the other name for this radio) as having an energised speaker.
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Ray P
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#37 Re: Next Year's project

Post by Ray P »

I promised some pictures, here are some of the bakelite enclosure;

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Ray P
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#38 Re: Next Year's project

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and some more;

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Ray P
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#39 Re: Next Year's project

Post by Ray P »

and some pictures of the bits that make the noise;

Image

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Ray P
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#40 Re: Next Year's project

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and more;

Image

Image

Image

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Dave the bass
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#41 Re: Next Year's project

Post by Dave the bass »

Pssssttt, mind that chain and BB tool on the floor MrP!
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Ray P
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#42 Re: Next Year's project

Post by Ray P »

As you can see, there is a seperate choke for the power supply and the speaker is just a normal 2wire job.
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Ray P
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#43 Re: Next Year's project

Post by Ray P »

Dave the bass wrote: Mon Nov 26, 2018 8:42 pm Pssssttt, mind that chain and BB tool on the floor MrP!
The chain is badly worn and destined for recycling...
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#44 Re: Next Year's project

Post by jack »

You may be able to get a replacement glass from either one of the two main UK vintage radio fora...

https://golbornevintageradio.co.uk/forum/index.php ("GVR", where I'm an administrator) or https://www.vintage-radio.net/forum/index.php ("UKVRRR").

Both are excellent and very helpful.

It's worth asking about a replaced speaker too. The one you have us obviously not original - the cones used tovrot at the edges and anyway, your radio has spent time in a damp garage or shed and the chassis shows that.

I had a dac90a like that once and did a complete strip down and bare-bones restoration. I wrote up a bit of it on UKVRRR some years ago.
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Ray P
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#45 Re: Next Year's project

Post by Ray P »

Thanks Nick. Although it's in a bit of a state I'm coming round to thinking that it doesn't deserve to be 'dumped' and to invest the time in bringing it back to life would be worth doing, if a bit daunting. I've concluded that the only worthwhile approach would be to do as for your DAC90, strip it back to the basic components and renovate/rebuild from a bare chassis. Please tell me if you think I'm being daft and it isn''t worth the effort?
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