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| Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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20th Jan 2021, 8:15 am
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#1 |
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Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Murphy radio set TA224
Dear friends.
In the schematic of the above set the rectifier valve used is UU9. It is a indirectly heated valve with a filament of 6.3V. In the schematic it is shown that the Pin no 7 i.e. cathode is connected to pin no 8 which is one end of filament. Why this is done? Thanks and regards P.Rajan |
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20th Jan 2021, 4:57 pm
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#2 |
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Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Murphy radio set TA224
Although the UU9 has isolated heater-cathode the insulation is only rated up to 300V and then only for vibrator power supplies. Why that should be so......
 .In the TA224 the UU9 heater is fed from its own isolated winding so linking the cathode takes the potential ill effects of h-k insulation breakdown out of the picture. It's not unheard of for higher quality radios using EZ80 and the like to do the same, even though it's not technically necessary.
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
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21st Jan 2021, 8:28 am
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#3 |
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Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Re: Murphy radio set TA224
Dear mr. Herald
Thank you very much Regards P.Rajan |
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