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Old 31st Dec 2016, 1:46 pm   #301
Stylo N M
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Default Re: My first valve radio project - Philips 462A

Well done Nicola, wow Lawrence what an expirence it's been, Nicola, there are still plenty of stations to pick up on MW and there's still RTE Radio 1 and Radio 4 on LW plus a few French stations too. Why not have a go. Something like a Bush DAC90A you would sail through that with ease.

Paul.
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Old 31st Dec 2016, 1:57 pm   #302
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Default Re: My first valve radio project - Philips 462A

You could try a 10nF for C24 but as it is a tone corrector using a 10x value will make the audio sound much more muffled.
There are still a lot of MW stations about, local radio stations and music type stations, it depends on what you listen to.

Mike
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Old 31st Dec 2016, 5:08 pm   #303
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Default Re: My first valve radio project - Philips 462A

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Originally Posted by indigo.girl View Post
Interesting what you say about trying to get a MW/LW set up and running next. I am tempted and feel a little guilty about not doing it for this one after being told off by Heterodyne. I think my issue was I don't really know what to do with a MW/LW set once I'm finished... what do people do with their MW/LM sets these days?
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Originally Posted by indigo.girl View Post
I'll replace C24 traders too then. I have a 10nF cap (630V). Is it OK to use this or is x10 a bit too high? It seems to be in general people can be quite flexible with cap and resistor values when replacing - is there a rule of thumb for what range you can use as a replacement?
I hope I wasn't telling anyone off, I just thought it a shame that a radio as good as a Philips was not going to be used in the way it was intended anymore. There is still plenty of stations on the medium wave to listen to. As for the tone correction C24 capacitor this should be close to the original value, the capacitive reaction is inversely proportional to frequency, meaning that as the capacitor gets larger the frequency it 'lets through' (though it is the influence of one side of the capacitor on the other side) gets lower, the impendence of the circuit also determines what size a capacitor in relation to the frequency it 'lets through' is. So if a larger capacitor is fitted to C24 it will give more treble cut. Earlier designs had the tone control variable resistor fitted here meaning the control had the full high tension voltage on it.
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Old 31st Dec 2016, 7:37 pm   #304
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Default Re: My first valve radio project - Philips 462A

I was just joking about the telling off Thanks for the advice on capacitance. I'll fit a 1nF in that case. I may well try out the AM receiver just to see if it works
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Old 31st Dec 2016, 9:48 pm   #305
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Default Re: My first valve radio project - Philips 462A

Make sure the on/off switch contacts are not dirty causing high resistance.
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Old 31st Dec 2016, 11:07 pm   #306
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Default Re: My first valve radio project - Philips 462A

I am afraid I was a bit late in posting,as what I answered to is long gone.
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Old 5th Jan 2017, 8:48 pm   #307
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Default Re: My first valve radio project - Philips 462A

I've replaced the two resistors and tidied things up and the set is working nicely. However, with bluetooth module installed I have an annoying volume-dependent buzzing through the speakers..

This is what I've done:
The audio input from bluetooth to the set has been wired in with a 47K resistor in series before going into the gram pick up socket. The bluetooth module is the kind that plugs into a USB port for its power. So I have opened up one of those 240V wall plugs that have a USB port and wired it directly into the sets on/off switch. So its only on when the set is on. The last time I did this in a radiogram I had an separate on/off switch for the blue tooth power so it could be switch off when I was playing gram or radio. When I switched the bluetooth off (but radiogram still on) I got loud buzzing because the bluetooth went very high impedance when off. This was solved by adding a 47k resistor across each channel input to ground. This time, by wiring into the sets on/off I have avoided the high impedance issue but this time get a buzz when the bluetooth is on. Could this be a proximity thing? I have the 240V-5V plug very close to the mains transformer in the set. Any ideas on what to try to stop the buzzing?
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Old 5th Jan 2017, 9:34 pm   #308
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Default Re: My first valve radio project - Philips 462A

I think the hum is being picked up on the (possibly unshielded) audio cable from the Bluetooth receiver to the PU sockets. This is upstream of the radio's volume control, so will be affected by that.

If so, it could be mitigated by careful routing of the audio cable away from the mains transformer, and / or by using shielded cable for this connection.
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Old 5th Jan 2017, 9:37 pm   #309
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Default Re: My first valve radio project - Philips 462A

I know zilch about Bluetooth but that unit looks too close to the mains transformer.

Lawrence.
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Old 5th Jan 2017, 11:59 pm   #310
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Default Re: My first valve radio project - Philips 462A

Bluetooth is digital. The module could simply be radiating RF c**p into the set.......
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Old 6th Jan 2017, 4:24 pm   #311
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Default Re: My first valve radio project - Philips 462A

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The audio input from bluetooth to the set has been wired in with a 47K resistor in series before going into the gram pick up socket. Any ideas on what to try to stop the buzzing?
Hi, I would suggest that you check to see that the 47K resistor is wired into the "live" or "grid" connection to your pick-up socket. I.E. the socket which hums if you touch it with a screwdriver when on gram. the other socket should be ground for audio, and should have a direct connection to the blue tooth unit. Tony
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Old 7th Jan 2017, 8:36 pm   #312
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Default Re: My first valve radio project - Philips 462A

FINAL UPDATE: The buzzing was stopped by moving the mains cable over to the side underneath the machine. It was interacting with one of the components but I don't know which one. The proximity of the bluetooth receiver to the transformer did not appear to be an issue.

So, here it is my Philips 462A in all its glory. Playing clear and loud and looking absolutely fantastic!! I love it and my friend saw it today and was knocked out by it and now wants one herself! Thanks for all the help, especially Lawrence of course. I have learnt so much on this journey and am dying to start on my next radio set (I have already got one in my sights but hopefully it will be a little more straight forward next time!).

The set plays digital music now rather than its original AM frequencies so its not a 100% restoration but it will now get used again rather than sitting covered in dust in someones attic. I decided to remove the AM frequency receiving components in the end so they can be used in a restoration by someone else (on sale in the offered section here if anyone's interested).

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Thanks again...until the next time....
Nicola
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Old 7th Jan 2017, 8:51 pm   #313
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Default Re: My first valve radio project - Philips 462A

I'm glad your project turned out as you wanted it too, it's polished up good as well, need another one now for stereo...

Keep at it.

Lawrence.
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Old 8th Jan 2017, 4:21 pm   #314
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Default Re: My first valve radio project - Philips 462A

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I decided to remove the AM frequency receiving components in the end so they can be used in a restoration by someone else
To be honest, they are unlikely to be of use elsewhere, any other radio will already have them. It's your radio to do with as you will, but wouldn't it have been much easier just to disable it.

PS. It does look good, though.
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Old 22nd Jan 2017, 3:00 pm   #315
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Default Re: My first valve radio project - Philips 462A

As this radio is now on eBay, the Forum has no further interest in it.
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