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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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22nd Sep 2020, 12:41 pm | #21 | |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
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Re: Voltage drop on Philips 730A
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John |
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22nd Sep 2020, 3:16 pm | #22 |
Hexode
Join Date: Oct 2006
Location: Edenderry, Republic of Ireland.
Posts: 428
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Re: Voltage drop on Philips 730A
Hi Johnny, I have just powered up the radio with no valves or dial bulb installed and I measured 4.45 volts on the heater/dial bulb winding. I left the red lead attached with the power supply switched off and the voltage started creeping up on the multimeter. It went up to almost 9volts . This to me might be the reason why the bulb is blowing but I do not know for sure. I now think that I may have to get a new transformer. Would one from a Cossor 484 in anyway suit . It is in a working chassis but the cabinet is long gone. Thanks again , Dick.
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22nd Sep 2020, 3:24 pm | #23 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: Voltage drop on Philips 730A
4.45V doesn't sound unreasonable for an unloaded 4V heater supply. It won't hurt a heater short term either- try plugging in all valves except rectifier and measure it again.
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22nd Sep 2020, 3:28 pm | #24 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
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Re: Voltage drop on Philips 730A
With no valves plugged in the LT voltage from the transformer will be high. A load ie the valve heaters is needed to drop the voltage. As explained several times if the voltage was high the heaters would blow as well as the dial lamps.
Have you verified that your meter is accurate and that you have the correct lamps?
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
22nd Sep 2020, 5:28 pm | #25 | |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
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Re: Voltage drop on Philips 730A
Quote:
What power supply was switched off? How can the voltage increase with it switched off. What is this red lead? Mike |
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