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Old 29th Nov 2015, 11:55 am   #1
Booyakka
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Default Blaupunkt Arkansas radiogram

Hello people.

New to the site and have this radiogram. Blaupunkt Arkansas Stereo model 450154 with Garrard 2025 record deck. I bought this about 6 months ago in full working order and it sounds absolutely amazing apart from a slight hum you can hear when the volume is at low level.

So I'm thinking of maybe a service on this. Is this something i can do my self or leave to a professional? I have had a look in the back and it does look quite dusty it may have never had a service in its life. So where do I start?

I am in Leeds, West Yorkshire, so if anyone knows of anybody who might service this for me? I have put a couple of pictures up too.

Thanks all for looking.
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Old 29th Nov 2015, 2:35 pm   #2
johnmarshmanagain
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Default Re: Blaupunkt Arkansas radiogram

Hi Boo
Welcome to the forum
It is, I'd say, normal that there'd be some hum, as not all the mains hum is removed, and this can be more noticeable at low volume. The consensus on this forum is that you should not drive yourself mad with the search for audio perfection, and to let matters rest. Anyhow, to look at the matter further you'll be wanting to download a circuit diagram for the particular model number, and then look for how the mains hum is dealt with - posting the relevant chunk of the scheme on this thread. There will (ideally) be a separate choke in a pi network with a couple of electrolytic capacitors, but chokes are expensive and often we find instead that a) a resistor has been used,or b) part of the audio output transformer's primary winding has been co-opted to the choke's purpose, which works less well. On a Pye radiogram I removed the filtering via the output transformer(s) and put in a nice fat choke instead, and certainly the hum did reduce a good deal - that said the choke was expensive (say 20 inc p&p). Cheers JM
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Old 29th Nov 2015, 3:27 pm   #3
TonyDuell
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Default Re: Blaupunkt Arkansas radiogram

I can't think of a single thing that can only be done by a professional (the legalities of doing it are another matter in some cases), suffice it to say that whether or not you are paid to do a job (amateur .vs. professional) has little to do with how good you are at it.

That said, I/we have no idea of your skill and knowledge level. Are you happy using small hand tools? Soldering? Can you read a circuit diagram? What test equipment do you have (if any)?

Why do you think it needs a service? It would do no harm to remove the dust (but do NOT disturb any of the preset adjustments on the circuit boards, you do not want to have to align this thing). It would possibly be a good idea to clean and lubricate the turntable (which is separate form the radio/amplifier unit).

If the hum is the problem, then I would first suspect the smoothing capacitor, This may be the cylindrical component on top of the mains transformer (left side of the chassis in the second picture) but without the service sheet I can't be sure.
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Old 29th Nov 2015, 3:27 pm   #4
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Default Re: Blaupunkt Arkansas radiogram

Hello,
As John says, a slight hum was perfectly normal in consumer equipment in the valve era. We're used to complete silence now, of course. If it doesn't intrude into normal listening levels I'd be inclined to let sleeping dogs lie.
If you do decide to go further, you need to decide whether to ask for someone to look into this, or ask for advice on doing it yourself. Your post is ambiguous, and conflicting advice will only serve to muddy the waters.
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Old 30th Nov 2015, 7:51 am   #5
Nickthedentist
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Default Re: Blaupunkt Arkansas radiogram

Bill, do you think this is a valve set, though? I'm not entirely sure looking at the pics.

N.
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Old 30th Nov 2015, 8:36 am   #6
Michael Maurice
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Default Re: Blaupunkt Arkansas radiogram

Quote:
Originally Posted by AC/HL View Post
a slight hum was perfectly normal in consumer equipment in the valve era.
This is a later fully transistorised version. The earlier valved sets tended to use the Garrard Autoslim deck.
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Old 30th Nov 2015, 9:00 am   #7
Booyakka
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Default Re: Blaupunkt Arkansas radiogram

Hi everyone thanks for taking the time and respond to my post, I am a practical guy and I do own a soldering iron but as for reading circuit diagrams and having any testing equipment that's a no. Well I suppose I could live with the slight hum it's not that bigger deal, what I forgot to mention is that when you move the volume knob you get a crackle but that stops as soon as you stop moving the knob. I think my best plan would be to have someone look it over and check it's all working as it should, can anyone help me or point me in the right direction.
Thanks
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Old 30th Nov 2015, 9:27 am   #8
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Default Re: Blaupunkt Arkansas radiogram

Ah, that's what I thought from the pictures, but it's hard to tell sometimes.
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Old 30th Nov 2015, 10:57 am   #9
AC/HL
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Default Re: Blaupunkt Arkansas radiogram

Oops, yes, the cabinet style is misleading. As you want someone to check it over I'll move this thread to the relevant section.
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