wayne
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Post by wayne on Jan 18, 2022 18:34:39 GMT 12
Hi all happy new year Can anyone help me identify these there are 2 of them in the radio Please note all the caps are marked as PF and 1500V except 2 which are 3750V and the elyt are 25 and275V any help much appreciated Regards Wayne
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6A8G.
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Post by 6A8G. on Jan 24, 2022 17:27:52 GMT 12
Forgive me if you've already tried this but have you tried measuring the capacitance? I've done this in the past &, more often that not the value is as marked. Note that if they are leaky the capacitance can read high.
Good luck/. John:)
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wayne
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Post by wayne on Jan 25, 2022 7:25:14 GMT 12
Thanks John Apologies as I didn't ask the right questions. It was what sort of capacitors are these as a novice I haven't seen them and couldn't find them using google. Does that type need to be replaced like the paper wax ones as the values are missing from the green paper that's wrapped around them although I can make out the 1500v I don't have the knowledge yet to try and track them down on a schematic. Thanks Regards Wayne
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6A8G.
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Post by 6A8G. on Jan 25, 2022 16:04:10 GMT 12
Hi Wayne, are the numbers on the caps referring to the value or the voltage rating?
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wayne
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Post by wayne on Jan 25, 2022 21:15:54 GMT 12
They refer to the voltage they are 1500V Thanks Wayne
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6A8G.
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Post by 6A8G. on Jan 30, 2022 7:28:29 GMT 12
Hi Wayne I've had a close look at the cap above the number 2 label & I'd swear the label shows 15000pf - I turned your photo upside down so the writing is the right way up. Have a closer look at that pic & se if you agree. Also if the other cap is of similar size it could be the same value?
Also, what part of the circuit are these in? It just seems that 1500 volts is a very high rating.
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wayne
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Post by wayne on Jan 30, 2022 13:30:42 GMT 12
Hi John thanks for that. What I managed to do was disconnect the cap and test it it wasn't leaking so I replaced it with one of equal value and another one of the same size. This radio was made in Sweden and all of the caps are rated at 1500v apart from 2 that according to the schematic that Steve kindly tracked down for me are 3500v I powered it up with my dim bulb tester and all good so took it off and powered it up normally, it goes for 1- 2 minutes then cuts out no sound I'm thinking of putting this in the to hard basket for now as I haven't the knowledge to figure things out I need to spend time trying to learn how to read a schematic and although I know how to replace some parts I need to know why they need replacing and what they do. Do you know what sort of capacitors those are in the picture ?
Hope that wasn't to much of a ramble Regards Wayne
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Steve
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Post by Steve on Feb 11, 2022 7:47:04 GMT 12
When things cut out after warming up I suspect two things primarily - solder joints and resistors. Old carbon resistors can crack, and heating up can cause the two halves to shift potentially breaking a circuit, or making it a higher (or lower) resistance. Use a plastic or wooden stick and start poking around before and after it cuts out. Solder joints can effectively do the same thing - dry joints can look perfectly fine until they get a little heat in them. And a dry joint can act as a resistor, meaning it can create its own heat. Again, start poking around - or even just reflow every joint with a little fresh solder.
This is not a guaranteed way to fix it - it could be something nefarious like a broken wire in an IF can or something hard to spot like that - but its where I would start if it wasn't clear where the problem was.
I then might pull out a signal tracer to check the grid of each valve (among other spots) for a signal to try and find out where the error occurs. Check when cold so you know what to expect, then check again when it cuts out.
Cheers, Steve
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wayne
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Post by wayne on Feb 12, 2022 18:13:33 GMT 12
Thanks Steve, interesting you say bad resistors as in my attempt to move it out of the way the wire came away from one end I managed to solder it so that will be my first place I will look. The description on the resistor ( I take it it's a resistor ) is 100ohm 0-1 it's all green in color what do I replace it with ? Thanks Cheers Wayne
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wayne
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Post by wayne on Feb 12, 2022 18:21:41 GMT 12
Adding to my previous post I had a look online in my attempt to identify the resistor I found 100ohm and the 0-1 refered to a tolerance ? Thanks Wayne
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wayne
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Post by wayne on Feb 13, 2022 10:54:12 GMT 12
Just an update. I had a poke around with a wooden stick and found a capacitor that when moved around made the sound cut in and out, looking at it it was a solder joint that I wasn't to proud of to did it again and all good so far it's been going well for half hour. Just out of interest can anyone let me know what sort of capacitors are the ones in my original post ? Thanks Regards Wayne
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Steve
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Post by Steve on Feb 14, 2022 8:48:37 GMT 12
they're most likely just wax-dipped paper and foil capacitors, just as you'd find in most radios of that vintage - perhaps in Sweden they preferred to read in pF rather that uF - it shouldn't make too much difference though - it just makes the number you read bigger, but the value will still be the same. You just need to convert the value (1000pF == 1nF == 0.001uF).
As for the resistor - pictures would help but I'd assume 100 ohm, 1/2W and replace it with 100 ohm 1 or 2 watt just because modern resistors are smaller and so 1W or 2W ones look better - and because the voltage rating of modern 1/2W resistors might not be suitable for all parts of the circuit.
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wayne
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Post by wayne on Feb 14, 2022 21:38:52 GMT 12
Thanks Steve Attached is a pic of the resistor I asked about I believe its called a dog leg On another project can anyone please help me with the following I wish to replace the electro can capacitor on top of the chassis of a Philco Radio type 1257 its a 40 40 20. I understand the markings for each value but they are not visible looking from under the chassis. which is the 20 tab ? I hope this makes sense so hear goes The orange wire goes eventually to valve EZ80 Yellow wire below that goes to the same valve Bottom yellow wire goes to to the off on volume Small yellow wire from the same tab as the yellow wire goes to valve N78 I had a look but couldnt find a schematic ( not that I can read them yet ) A bit of a ramble but hope it makes sense Thanks Wayne Sorry cant get the photos sorted yet
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wayne
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Post by wayne on Feb 14, 2022 22:24:50 GMT 12
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6A8G.
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Post by 6A8G. on Feb 15, 2022 10:31:05 GMT 12
Hi Wayne, these caps usually use small icons for the values. I can't see them in your photo so they may be between the tags & the chassis. They are usually stamped into the brown phenolic base & they are typically a square, a triangle & at half-round. There should be a legend on the side of the can denoting which values are assigned to which cap. Best, John:)
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