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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 11th May 2021, 12:54 pm   #1
Dorian27
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Default Orion EA53F

Can any one tell me what resistor value this is please and where I would get a suitable replacement from thank you
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Old 11th May 2021, 3:58 pm   #2
cathoderay57
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Default Re: Orion ea53f

You can download the circuit diagram from RadioMuseum here: https://www.radiomuseum.org/r/orion_ea53fea_53.html . You do not have to be a member, just click on the image of the circuit and follow the instructions. If the subject resistor is the one across the 2 terminals of the main HT smoothing capacitor then it is 1k. It is dropping 30v therefore it is dissipating 0.9W. To replace it you need some margin. A 2W would probably be alright but would get quite hot. If it were me I'd use a 5W because it would run a bit cooler. You also need to ask yourself why the existing component has got so hot, or burned out, if indeed it has. A possible cause is a leaky HT capacitor but there is a multitude of other possible reasons for higher than expected HT current including a leaky grid1 coupling capacitor on the audio output valve causing it to pass too much current. Hope that helps. You shouldn't have any difficulty finding a replacement resistor on eBay or any component supplier. Jerry.
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Old 11th May 2021, 8:47 pm   #3
Dorian27
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Default Re: Orion ea53f

Hi Gerry thank you for help i am quite a novice so I don't know which is the HT COUPLING capacitor I have downloaded the circuit diagram as you said. Thanks.
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Old 11th May 2021, 9:42 pm   #4
Gabe001
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Default Re: Orion ea53f

A hexode is a novice?

Lots of information here to get you started:

http://www.vintage-radio.com/repair-...ion/index.html

Specifically, the grid coupling capacitor and associated faults (as mentioned by Jerry) are explained here:

http://www.vintage-radio.com/repair-...ut-stages.html

Gabriel
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Old 11th May 2021, 10:09 pm   #5
cathoderay57
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Default Re: Orion ea53f

Identifying components in this case is tricky but I'll do my best. It's against Forum rules to attach RadioMuseum circuits in entirety and the file is copy protected so I can't do clips. The components are depicted with values and don't have component numbers. The main HT smoothing capacitor is shown near the bottom left of the first page of the circuit to the right of the EM84. It is a twin capacitor with values shown as 2 x 50u/380v. On the chassis it will be an aluminium can with 2 prongs sticking out the bottom under the chassis with the 1k resistor soldered across them, as shown in your photo. In the circuit, the grid1 coupling capacitor is immediately to the right of the ECL82 and has a value 56n i.e. 56 nanofarads or 0.056 microfarads. It is connected between the ECL82 triode anode (pin 9) and the ECL82 pentode grid1 (pin 3) via a 10k resistor. If it is leaky you need to replace it with one with a voltage rating of at least 350v. Jerry
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Old 12th May 2021, 12:57 pm   #6
Dorian27
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Default Re: Orion EA53F

Hi I have taken this out and put it on a meter it reads 69nf and 7% v/ loss is this OK or do I need to replace it. If so what exactly do I get as a replacement as I am not sure.
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Old 12th May 2021, 1:21 pm   #7
Gabe001
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Default Re: Orion EA53F

Most people would replace this always, as the consequences of failure can be so dramatic.

You can replace with a 47nf (or even 68nf) axial polypropylene capacitor rated 630v (unless the original is rated higher)
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Old 12th May 2021, 2:22 pm   #8
cathoderay57
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Default Re: Orion EA53F

The component might or might not be OK. Low voltage tests on a meter can be misleading since they do not stress the component anywhere close to its normal working voltage. If the HT power supply of the set were working you could disconnect the low voltage end (the one connected to the 10k resistor) and put the meter probes, using voltmeter setting, between the disconnected lead and chassis. Switch on the set and, if the cap is OK, the meter should show an initial indication then quickly reduce to zero. Since presumably the HT is not yet working, then Gabriel is right, the best approach is to simply replace the cap with a new one. In fact you can easily get the exact value for not much money on eBay such as this https://www.ebay.co.uk/itm/193259585981. As I said the cap's working voltage needs to be at least 350v.
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