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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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28th Jan 2019, 11:19 am | #1 |
Diode
Join Date: Sep 2018
Location: Colchester, Essex, UK.
Posts: 7
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Codar PR30x HT voltage high?
Have bought this on ebay, it looks to be in good condition. The problem I have is that the ht voltage is 335volts to high for a ef183 valve. The instructions say the output to the connector on the back of the unit should be 200volts not 335volts. I have checked all component values which seem to be ok. the ac output from the mains transformer is about 230 volts. If anyone else has one of these units I would like to know what voltage they are getting.
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28th Jan 2019, 11:57 am | #2 |
Nonode
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 2,034
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Re: Codar PR30x HT voltage high?
If the output of the transformer is measured at 230 volts, I would expect to see 1.41 times this after the rectifier, so about 330 volts off-load. Is the valve OK, heaters lit, drawing current etc? Does this unit have a mains voltage selector, and if so is it on the right tap?
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Andy G1HBE. |
28th Jan 2019, 2:17 pm | #3 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 947
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Re: Codar PR30x HT voltage high?
Hi the one i have is with ext power supply it states for that one 180-250v ht
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28th Jan 2019, 3:12 pm | #4 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Codar PR30x HT voltage high?
I would suspect that the mains transformer has been replaced at some time? A picture would confirm it.
A 160 or 170 volts AC secondary would get you 240 or 250 volts DC. Alan Last edited by snowman_al; 28th Jan 2019 at 3:15 pm. Reason: Picture |
28th Jan 2019, 4:56 pm | #5 |
Diode
Join Date: Sep 2018
Location: Colchester, Essex, UK.
Posts: 7
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Re: Codar PR30x HT voltage high?
The valve has tested as being faulty, I have a replacement but I am reluctant to plug it in until I have reduced the voltage. I have attached a photo of the inside of the unit, it looks original to me!
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28th Jan 2019, 7:15 pm | #6 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Codar PR30x HT voltage high?
That does all look original and as it should be...
Is there a 'bleed' resistor across the HT+ to ground? (100k ish?) |
28th Jan 2019, 11:10 pm | #7 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,152
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Re: Codar PR30x HT voltage high?
Power supplies like these will usually have a high voltage on their output if no current is being supplied.
Once the valve heater warms up and the valve starts to conduct, the HT voltage will drop. The EF183 is rated up to 250V and cathode current may be 13mA. If you remove the valve and connect a 20K 5Watt resistor across the power supply HT you will get an idea of the normal HT voltage. |