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23rd Oct 2010, 7:39 am | #1 |
Hexode
Join Date: Nov 2006
Location: Biedenkopf, [Hessen], Germany.
Posts: 425
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Building a tube Ghetto Blaster
hello friends,
after a very long time of planing I have started to build a homebrew tube Radio in "ghetto blaster desgin". My idea was, to have this very special case design. The plan... AM/FM stereo superhet with IF 455kHz AM and IF 10,7mc FM, including tube stereo decoder and "3D Sound". 3D sound, some old german radios use this, is simply to insert additional 2 speakers in the right and left side of the case, the sound power amp use 3 transformers, one SE for left, one SE for right, and a center PP for front, all this with only 2 power tubes. I will do it with 6AQ5 = EL90. The special problem to build a ghetto blaster design is the very small space inside, the project will not go without exactly mechanical plan and design. The Deepness of the case cannot be large, a question of design. So I made the construction : <--> 500mm height: 200mm deep: only 125mm ( 1" = 25.4mm) The "buttons" have to look like cassette player buttons of a ghetto blaster.. The tuning scale, I decidet to make a hallicrafters design to it. The magical eye tube, small and nice, EAM86 Upside a cover, containig the ferrite antenna, cooling, pots. 2 telescope antennas. wood case for good tube sound. Black glossy painting. aluminium parts for small weight. a lot of fun and a lot of time ! Now, start When I`m finished, I will give exactly plan of construction for a easy rebuild. greetings Martin Last edited by 6AL5W-Martin; 23rd Oct 2010 at 7:54 am. |
23rd Oct 2010, 7:51 am | #2 |
Heptode
Join Date: Feb 2007
Location: West London, UK.
Posts: 867
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Re: building a tube ghetto blaster
Look forward to seeing some photos when it is finished. Hope you have got room for batteries, assuming it is portable.
John |
23rd Oct 2010, 8:38 am | #3 |
Retired Dormant Member
Join Date: Mar 2009
Location: Zala, Hungary
Posts: 418
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Re: building a tube ghetto blaster
Yes, if it's as loud as it looks you may need big batteries!
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23rd Oct 2010, 9:55 am | #4 |
Hexode
Join Date: Nov 2006
Location: Biedenkopf, [Hessen], Germany.
Posts: 425
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Re: building a tube ghetto blaster
I think that will not be possible,
this radio will blow out 6 to 8 Watt, what means, with battery tubes it`s not possible. a 6AQ5 will eat roundabout 10Watt Anode + 3A heating, there are 2 ... Maybe I use a seperate Bag with 12V7Ah and a low cost transverter. The radio self, 230v~ greetings Martin |
23rd Oct 2010, 10:05 am | #5 |
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Re: building a tube ghetto blaster
I used to do that, build the box first and then try to fit it all in. Always ended up with a very cramped bit at the end.
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23rd Oct 2010, 12:55 pm | #6 |
Rest in Peace
Join Date: Dec 2008
Location: Burton upon Trent, East Staffordshire, UK.
Posts: 1,686
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Re: building a tube ghetto blaster
In my younger days, when working for a well known hi-fi manufacturer, that was always how it was done. Marketing said 'This is the size/shape/colour/facilities we want' and the Designers had to get it all in.
It wasn't always an unqualified success Alan |
23rd Oct 2010, 5:26 pm | #7 |
Retired Dormant Member
Join Date: Dec 2005
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Re: building a tube ghetto blaster
The case looks a really strong job, but a bit risky to build this first. I would start with a large chassis then work from the centre outwards,get the design working ,then trim the chassis to minimum requirements. A bit tedious I know but it could save a lot of frustration.
Good luck anyway. Mike |
23rd Oct 2010, 7:31 pm | #8 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: building a tube ghetto blaster
Wouldn't it be easier to start from one end- then you would only need to trim off one bit
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23rd Oct 2010, 7:50 pm | #9 |
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Re: building a tube ghetto blaster
You could always use something like an ELL80 (?) to get the valve count down. I'm not sure but think there is a triode/twin pentode valve, maybe an ECLL80? too.
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23rd Oct 2010, 9:25 pm | #10 | |
Dekatron
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Location: Croydon, Surrey, UK.
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Re: building a tube ghetto blaster
Quote:
SB
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23rd Oct 2010, 10:14 pm | #11 |
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Re: building a tube ghetto blaster
If it has a common cathode, you wont be able to use the triode section as a phase splitter, assuming of course you wanted push pull output stages.
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23rd Oct 2010, 11:47 pm | #12 |
Rest in Peace
Join Date: Dec 2008
Location: Burton upon Trent, East Staffordshire, UK.
Posts: 1,686
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Re: building a tube ghetto blaster
The rsdiomuseum doesn't agree - see
http://www.radiomuseum.org/tubes/tube_ecll800.html However, it does depend on your definition of phase splitter. Alan |
24th Oct 2010, 12:55 am | #13 |
Dekatron
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Location: Leominster, Herefordshire, UK.
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Re: building a tube ghetto blaster
Clever! Presumably the triode only manages unity gain. It must have a low gm, ra or both.
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24th Oct 2010, 7:39 am | #14 |
Hexode
Join Date: Nov 2006
Location: Biedenkopf, [Hessen], Germany.
Posts: 425
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Re: building a tube ghetto blaster
hello Friends,
ELL80 and ECLL800 are tubes with a short life time, also they are rare and very expensive. So i decidet to 6AQ5 (7pin), a low cost tube with enough output. EL95 (=a half ELL80) is better, only 0,2a filament, but it requires 10k A-A greetings Martin |
24th Oct 2010, 9:04 am | #15 |
Moderator
Join Date: Feb 2006
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Re: building a tube ghetto blaster
I stand corrected!
Ingenious |
24th Oct 2010, 12:23 pm | #16 |
Pentode
Join Date: Nov 2005
Location: Tircoed Forest Village - Swansea, UK.
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Re: building a tube ghetto blaster
Can't wait to see the finished system...
Bob W
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24th Oct 2010, 4:42 pm | #17 |
Hexode
Join Date: Nov 2006
Location: Biedenkopf, [Hessen], Germany.
Posts: 425
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Re: building a tube ghetto blaster
one of the tricks to keep space is, to put the filters in downside of the chassis,
they must not have case, only a little aluminium separation plate. Some filter coils can be wired on amidon toroids (not all). The (hot..) audio stage will be flown upsid, behind the scaling. I have planed in Corel, but its a fight for every space But the switching area will look , like most tube radios, not so perfect, short wires and a lot of coils there greetings Martin Last edited by 6AL5W-Martin; 24th Oct 2010 at 4:50 pm. |
25th Oct 2010, 9:04 am | #18 |
Retired Dormant Member
Join Date: Dec 2005
Location: Wisbech, Cambridgeshire, UK.
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Re: building a tube ghetto blaster
Sorry Chris, starting from one end and trimming off the other would not work, perhaps I should explain. I place all the major components on a large sheet of aluminium and when I am happy with the layout I cut all the holes for the valve sockets transformers ect. This is far easier to do anyway on a flat sheet than on a folded up box. I then trim and fold the sides to form the chassis, both operations being done with a Warco bending jig. Admittedly this method does produce a small amount of waste but not as much as finding you have to start from scratch as you find you cannot fit everything in.
Mike |
27th Oct 2010, 6:44 am | #19 |
Hexode
Join Date: Nov 2006
Location: Biedenkopf, [Hessen], Germany.
Posts: 425
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Re: building a tube ghetto blaster
Continue
The "buttons" have to look like cassette player buttons of a ghetto blaster.. ... done. next step comming soon: Dial. greetings Martin Last edited by 6AL5W-Martin; 27th Oct 2010 at 6:49 am. |
27th Oct 2010, 7:46 am | #20 |
Hexode
Join Date: Apr 2009
Location: Naples, Florida, USA
Posts: 255
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Re: building a tube ghetto blaster
Add a spot for an iPod dock or at the very least an iPod/mp3 input. Looks great.
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