UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 28th Jan 2019, 11:19 am   #1
Tonyohall
Diode
 
Join Date: Sep 2018
Location: Colchester, Essex, UK.
Posts: 7
Default 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.
Tonyohall is offline  
Old 28th Jan 2019, 11:57 am   #2
Andrew2
Nonode
 
Andrew2's Avatar
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 2,034
Default 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?
__________________
Andy G1HBE.
Andrew2 is offline  
Old 28th Jan 2019, 2:17 pm   #3
mickm3for
Heptode
 
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 947
Default Re: Codar PR30x HT voltage high?

Hi the one i have is with ext power supply it states for that one 180-250v ht
Attached Files
File Type: pdf Codar PR-30 Pre Selectr (1).pdf (1.14 MB, 78 views)
mickm3for is offline  
Old 28th Jan 2019, 3:12 pm   #4
snowman_al
Octode
 
snowman_al's Avatar
 
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
Default 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
snowman_al is offline  
Old 28th Jan 2019, 4:56 pm   #5
Tonyohall
Diode
 
Join Date: Sep 2018
Location: Colchester, Essex, UK.
Posts: 7
Default 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!
Attached Thumbnails
Click image for larger version

Name:	P1020813.jpg
Views:	119
Size:	96.4 KB
ID:	177270  
Tonyohall is offline  
Old 28th Jan 2019, 7:15 pm   #6
snowman_al
Octode
 
snowman_al's Avatar
 
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
Default 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?)
snowman_al is offline  
Old 28th Jan 2019, 11:10 pm   #7
Silicon
Nonode
 
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,152
Default 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.
Silicon is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 2:01 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.