wayne
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Post by wayne on Oct 5, 2021 22:01:24 GMT 12
Hi all, I'm going to replace the caps on this radio but looking at the schematic it shows the two electrolytic capacitors with a value of 8UF but the ones in the chassis are 50 and 32UF. I'm learning as I go so can anyone help me understand this or have I missed something With electrolytic capacitors, when checked after disconnecting them if they show the value they are supposed to be can that mean they are okay or can they still not work properly under load when fitted. Hope this makes sense
Thanks
Wayne
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Steve
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Post by Steve on Oct 5, 2021 22:54:14 GMT 12
Wayne, the point of failure on those old caps is their ability to withstand high voltage more than their value changing - they can read their value fine on a modern cap tester or multimeter with capacitance mode. These modern devices will only test them with a few volts - but in the radio, under hundreds of volts, they will fail.
The EZ40 in that set will take a maximum reservoir cap (first one after the rectifier) of 50uF so that should be fine, and 32uF will also be fine. The difference between 8uF and 50uF might raise the HT a little bit but I don't foresee any issues.
Cheers, Steve
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wayne
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Post by wayne on Oct 6, 2021 11:26:59 GMT 12
Steve thanks for that. As I have them in stock do you think I could use 40UF caps instead of the 50 and 32 and the schematic shows a ECH42 the one in the radio is a Mazda valve 6C10 ?
Thanks
Wayne
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Steve
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Post by Steve on Oct 6, 2021 11:57:12 GMT 12
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wayne
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Post by wayne on Oct 6, 2021 12:20:29 GMT 12
Thanks again
Cheers
Wayne
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wayne
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Post by wayne on Oct 9, 2021 14:11:18 GMT 12
Hi all Ive replaced all of the caps and the power cord being very careful to replace things where I took them from. I powered it up and all I get on the broadcast Chanel is a continuous ticking tapping sound from the speaker which changes in volume when turning the volume control. Any ideas as to what the problem is ?
Thanks
Wayne
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Post by Richard on Oct 9, 2021 15:48:13 GMT 12
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wayne
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Post by wayne on Oct 9, 2021 17:10:39 GMT 12
Thank you for that At the moment I have no idea what B+ means or where to put that capacitor .I will have a look at the link you posted
Regards
Wayne
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Post by Richard on Oct 10, 2021 8:15:19 GMT 12
Thank you for that At the moment I have no idea what B+ means or where to put that capacitor .I will have a look at the link you posted Regards Wayne B+ is an old term related back to battery sets, meaning "Battery positive", its the High voltage positive DC supply, Across C35 in your schematic is where I would try the .1uf cap. Electrolytics are not good at bypassing RF and you don't want any stray RF on the B+ Give it a try, it may not be the fix? but faulty capacitors are usually the problem with motorboating, that's when you need to read that article, to try and work it out. I hope you are aware of the deadly voltages in a valve radio?  |
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Post by Richard on Oct 10, 2021 8:42:31 GMT 12
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wayne
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Post by wayne on Oct 10, 2021 9:24:36 GMT 12
Hi Richard thanks for that. Firstly yes I am very aware of the high voltage in the radios and I won't do anything unless I check things out. Interesting you mention faulty capacitors as I have replaced all capacitors including the electrolytic ones. I will read the article today and I'm going to a meeting with the Wellington branch of NZVRS this afternoon so I will take the radio and show the guys there. I am keen to learn and be told if I'm doing something wrong or silly.
I'll send an update later
Regards
Wayne
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wayne
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Post by wayne on Oct 11, 2021 13:51:13 GMT 12
Hi Richard I went to the meeting yesterday and the guys said the same as you re motor boating. I've fitted the capacitor and it appears problem solved. I think with a longer Arial and the alignment checked it will be good. I'll update later.
Something scary when I picked up the radio from trade me someone had fitted a 3 pin plug to the red Arial wire and the black earth wire I hope they had not plugged it in and turned it on
Regards
Wayne
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Post by Richard on Oct 11, 2021 14:15:00 GMT 12
Excellent news that you've fixed the motorboating. You'll know if they have plugged the Antenna wires into the mains as you wont have continuity of the Antenna coil and reception wont be good, if at all. I suspect it will be blackened anyway ?
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wayne
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Post by wayne on Oct 11, 2021 19:39:41 GMT 12
I have to restore the case as it's looking very sad along with restringing the tuning
Can I ask what sort of reading I should get when checking continuaty between the antenna and earth wires
Thanks for your help
Regards
Wayne
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Post by Richard on Oct 12, 2021 6:43:30 GMT 12
something like 20 ohms more or less , between the aerial and earth wires, you'll know if its faulty, because there will be NO continuity between these two points.
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