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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 7th Apr 2017, 1:43 pm   #241
Boater Sam
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Default Re: Restore a Beau Decca

Well, the one on the photo is leaking and needs to go. If they are like this then replace them certainly.
0.1uf is unusual for an electrolytic.

The bladed plug goes straight into a standard Octal, no modification require.
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Old 7th Apr 2017, 1:51 pm   #242
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Default Re: Restore a Beau Decca

And I always thought these had a RF stage!?
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Old 7th Apr 2017, 1:52 pm   #243
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Default Re: Restore a Beau Decca

I don't think they're electrolytics.

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Old 7th Apr 2017, 5:49 pm   #244
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Default Re: Restore a Beau Decca

They are not electrolytics, they are paper/wax capacitors referred to as waxies on here but encased in the tubular can with a bolt as part of the can.

You must treat trhem like any other paper/wax capacitors and as far as I'm concerned, that means replace on sight.
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Old 7th Apr 2017, 6:47 pm   #245
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Default Re: Restore a Beau Decca

Thanks Michael Maurice. I will go ahead and replace them.
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Old 14th Apr 2017, 4:52 pm   #246
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Default Re: Restore a Beau Decca

The Decca Decola radio is littered with them. Although still well sealed, I checked the leakage of a few and they were all bad. Not got around to doing it yet mainly because it needs a technique to open the can with minimal damage.
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Old 14th Apr 2017, 5:17 pm   #247
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Default Re: Restore a Beau Decca

I re stuff cans like this by cutting one end off with plumbers rotary tube cutter, it leaves a clean square end if done slowly and gently.
Then you can warm them and pull the guts out. A 1 mm drill in the centre through both ends for the new leads, stuff a new cap in and fill and refit the end with hot melt glue. The joint will be barely visible but it can be disguised as the band marking the outer foil by putting a thin section of black heat-shrink over it.

I still prefer to do a tidy re-stuff, I have been told that its anal, but I think it is a mark of my skill.
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Old 16th Apr 2017, 1:38 pm   #248
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Default Re: Restore a Beau Decca

Thanks for this. I've decided to piggyback then new capacitors alongside the existing ones. However have run out of 0.1caps so have ordered some more- here is a photo of WIP.
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Old 16th Apr 2017, 1:46 pm   #249
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Default Re: Restore a Beau Decca

But you have disconnected the old ones that are leaky?

Sorry if that's to obvious but from the way it reads, you have left them connected. Just being cautious.
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Old 16th Apr 2017, 2:01 pm   #250
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Default Re: Restore a Beau Decca

Thanks boater sam. Yes I have dis-connected the old ones, but thanks for the warning -always best to be sure!
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Old 27th Apr 2017, 12:33 pm   #251
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Default Re: Restore a Beau Decca

I've now completed re-capping the radio and constructed a lead. The circuit for the lead is shown- I've connected the 2 heater wires, the HT +ve and Gnd and the signal lead -which is screened. So far these are the only pins I've connected.


I've powered up the radio using the lamp limiter. The valve heaters are illuminated, the 'magic eye' glows, although dim, and the dial lamp illuminates. However no stations are found when I tune on any band- just hum. I've tried attaching the screen to Gnd, but still the same.

Any recommendations welcome as to how I should proceed. I've attached pictures of the Octal lead circuit and chassis.
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Old 27th Apr 2017, 1:24 pm   #252
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Default Re: Restore a Beau Decca

Did you recapp the radio all in one go or did you stop after each cap and check?

I use a limiter and try the radio after each cap I've replaced, in the early days I made the mistake of replacing lots of caps at once, made a bit of a mess and had to sit and retrace everything to get it to work.
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Old 27th Apr 2017, 3:51 pm   #253
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Default Re: Restore a Beau Decca

Thanks records. I got the impression (perhaps wrongly) that the paper caps were so old and unreliable that they should be replaced before power up. For this reason I did the replacement before connecting to the AMP.
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Old 27th Apr 2017, 4:35 pm   #254
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Default Re: Restore a Beau Decca

Replacing all suspect looking caps in go can actually add to problems of fault finding. Yes, they will be old, but not all are necessarily faulty.
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Old 27th Apr 2017, 5:22 pm   #255
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Default Re: Restore a Beau Decca

Thanks Edward. In hindsight I guess I should have waited to replace them. However based on where we are I would welcome any suggestions -especially relating to whether if I have made all the necessary connections on the octal lead between amp and radio unit.

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Old 28th Apr 2017, 10:56 pm   #256
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Default Re: Restore a Beau Decca

When I last re-capped one of these, I did the lot in one go, mine also didn't work because I'd inadvertently got a couple of resistors in the wrong place.
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Old 29th Apr 2017, 10:26 am   #257
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Default Re: Restore a Beau Decca

Thanks MM and EH. Looks like I've made an error in replacing these all at once! To attempt to rectify this it is probably best if I return it to the original condition- this time checking function after each change. However to do this properly I need to know that I've wired up the connecting lead correctly.

If anyone owns a beau decca I'd be extremely grateful if you are able to buzz out the connections between the 2 octal connectors. I've only connected 5 pins, but looking at the back of the octal plug on the radio there are 7 connections- some are indicated on the circuit as connected together but its not clear to me if this is in the radio or via the lead- hence verification of what the lead should look-like before I do any more cutting about or the radio would be a sensible this time I think!
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Old 29th Apr 2017, 10:59 am   #258
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Default Re: Restore a Beau Decca

Looking at the circuit and your drawing I'd say that your interconnecting lead is wired correctly.

I note that SOCKET 1 is only connected to the circuit at the radio end, perhaps this is the screen connection? SOCKETS 1 and 4 are connected together at the radio end. You can check this by doing a continuity test.

I haven't read the whole thread, but do you get anything from the speaker if you feed a signal into the Pick Up sockets? With PU selected of course. Just touching the PU sockets with a screwdriver generally results in a click, bang or buzz.
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Old 30th Apr 2017, 2:02 pm   #259
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Default Re: Restore a Beau Decca

Thanks Station X. Yes a continuity check on pins 1 and 4 shows they are connected together at the radio. I am using pin 4 as the screen. With this not connected there is loud hum as might be expected.

With the gram AMP on the radio setting, there is no sound from the speaker- not even hiss regardless of whether radio volume is high.

If I touch Pin 5 with a screwdriver, the effect is different depending on whether the radio volume is high or low:

When radio volume low: touching pin 5 with screwdriver produces moderate mains hum but no crackle.
When radio volume high: touching pin 5 with screwdriver produces moderate mains him and some high freq crackle.

Perhaps this info can help direct me in which capacitors I should work on first to put back to original config??
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Old 30th Apr 2017, 4:42 pm   #260
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Default Re: Restore a Beau Decca

It does sound like the amplifier section is working correctly. Injecting an audio signal at the pickup sockets would confirm this.

As far as the caps are concerned you'll have to look at each replacement cap and compare its connections with the circuit diagram.

Taking voltage readings on the valves in the radio section might provide a short cut to locating which stage is faulty.
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