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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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13th Aug 2019, 3:56 pm | #1 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Grundig Melody Boy 1000 - Sound But No Music
Hi,
Sorry if this is a really simple question and fix but I've never worked on radio before (I've worked on other electronics so I do have some experience and know-how) I have a Grundig Melody Boy 1000 which I picked up yesterday and plugged in, and it worked. I was listening to it for about an hour when the music just stopped. There was still sound from the speaker, a humming, but no music or static depending on how it was tuned. This was the same on all 5 bands. I turned it off for a bit and then turned it back on, and it worked again, and then for about an hour or so again it worked, until it stopped and just speaker hum with no actual radio sound. I've tried it on both Mains and Battery. Battery doesn't seem to work but mains does (Dial light and humming) I left it over night and turned it on today to see if it'll work and it doesn't, still just a humming speaker. I have opened it up to see if there could be any loose connections but there doesn't seem to be. What could cause this and how can I fix it? Sorry again if it is a silly question Thank you |
13th Aug 2019, 6:10 pm | #2 |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Grundig Melody Boy 1000 - Sound But No Music
Do you have any test equipment that would allow you to inject signals so that you could work back from the output stage to identify in which area the fault lies?
If no, you can improvise a simple source by using another radio. Take a feed from across the volume control and connect it to the Grundig's volume control when it goes off - you may find that, like a lot of Grundig radios it has a dedicated Pick-up input. If you can get sound from the other radio out of the Grundig, you will have eliminated the audio stages. Assuming you have a meter, take and note voltage readings at various stages while the set is working then repeat when it stops working and look for differences. |
13th Aug 2019, 6:37 pm | #3 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Re: Grundig Melody Boy 1000 - Sound But No Music
Hi,
No I don't have any test equipment like that but I have many other radios which I can use. How do I connect the two radios? I've never done this before so I'm not sure where to connect? Sorry again if it's simple. I have a meter but cannot use at the moment as the pins have snapped. Thank you for your help |
13th Aug 2019, 7:04 pm | #4 |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Grundig Melody Boy 1000 - Sound But No Music
Assuming they both have rotary volume controls, when viewed from the spindle end look at the three tags. With them at the top, the chassis connection is on the right and the audio input is on the left. Obviously if viewed from the back, the connections will be reversed.
Simply connect two wires to the same tags on the other set. Ignore the centre connection. The Grundig volume control should now function normally. WARNING Do not use a mains radio with a live chassis for this! |
13th Aug 2019, 7:29 pm | #5 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Re: Grundig Melody Boy 1000 - Sound But No Music
Hi,
Is this okay to do as the Grundig is a mains set and uses sliders, but I don't think the sliders should matter. (At the moment, I can't connect any batteries to it) I can use my RAD 24 which is battery only and rotary but I don't know if it has a live chassis. I wouldn't think so as it doesn't run off mains at all. Thanks |
13th Aug 2019, 7:59 pm | #6 |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Grundig Melody Boy 1000 - Sound But No Music
The Grundig will be mains isolated, so will be fine. As it uses sliders, you should find it easy to see which end is which!
A battery only set cannot have a live chassis! |
13th Aug 2019, 8:25 pm | #7 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Re: Grundig Melody Boy 1000 - Sound But No Music
Okay thank you, I'll get to doing that!
I didn't think they could have a live chassis but better safe than sorry. I'll report back once done! Thank you for your help |
14th Aug 2019, 10:08 am | #8 | |
Rest in Peace
Join Date: Nov 2010
Location: North Hykeham, Lincolnshire, UK.
Posts: 515
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Re: Grundig Melody Boy 1000 - Sound But No Music
Quote:
If you have a crocodile clip handy, put that on the negative lead so that you can clip it on the chassis, which makes life much simpler! |
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14th Aug 2019, 6:15 pm | #9 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Re: Grundig Melody Boy 1000 - Sound But No Music
It was the pins that snapped off the wire. They were very cheaply made. I'll be getting some better quality ones. I can do that for now.
I wont be doing anything with it just yet as I'm going on holiday tomorrow so i'll let you know in a while how I got on Thank you for your help, much appreciated |
15th Aug 2019, 9:35 am | #10 |
Octode
Join Date: Feb 2007
Location: Harrow, London, UK.
Posts: 1,483
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Re: Grundig Melody Boy 1000 - Sound But No Music
This is a high quality radio which uses a series regulator in the power supply and when working will give you the quality of sound for which Grundig were famous for.
I suggest you download the schematic as the symptoms you describe suggest thermal runaway in either the series regulator or audio output, caused by a faulty component or the rectifier, after years of use, has given up. To address this, using the set on batteries would be my first choice. The fact that battery operation isn't or wasn't possible makes narrowing down the fault difficult as you cannot bypass the internal power supply. The switch battery/mains must of course be placed in the correct position. Perhaps the first challenge is to find out why battery operation wasn't possible. Has the previous owner "been at it?" Using a battery supply will allow you to eliminate or confirm the internal power supply is functioning and if necessary delve further. From memory, the dial lamp is not in circuit when using the battery and should you be unaware of this it could lead you a merry dance. There is no need to make up wire probes etc to check the audio stage as the DIN audio socket gives you both audio in and out from the radio. Indeed, unless you are familiar with the loudness circuit used on this radio, you could misread the result. Last edited by simpsons; 15th Aug 2019 at 9:52 am. Reason: additional information |
29th Aug 2019, 11:50 pm | #11 |
Octode
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,306
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Re: Grundig Melody Boy 1000 - Sound But No Music
Hi,
Sorry for the late replies. I'll get a schematic and when I can get some DMM Probes I'll start a search around inside. As for the battery test, I couldn't test as I don't have any of the right batteries at the moment, but i'll try get some soon to test. I tried the set on mains and connected the DIN socket to a tape deck and have managed to get sound onto cassette from the radio via the DIN. Hope that helps Thanks for your help |