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 Post subject: Another Crosley 655 question and a prblem.....
PostPosted: Oct Sun 18, 2020 1:31 am 
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Joined: Jan Thu 20, 2011 5:18 am
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Location: Cottage Grove Oregon; 97424
First, on the schematic item number 21 is listed as a 1. Condenser since the schematic does not say Electrolytic either for the electrolytics or for number 21 would it also be an Electrolytic cap or just a "normal" non polarized cap? I only have one of those left, a 1.5 mfd.

Second, when I first looked under the chassis of this radio the first thing I saw was some one had changed the original Electloylytics out and maybe two other caps as they were different brands. One wire from the power transformer was broken off of where it should go. But where exactly does it go? is the problem. On reduced power, the transformer gets very warm and today there was a wisp of smoke coming out of the transformer holes in the chassis! Immediate shutdown. The wire in question is black with a faded red tracer and reaches to the attaching point of the on/off switch wires and that is where I was sure it had broken off from.

I installed a fuse in one side of the AC line as well, and it has not blown. I have recapped the whole radio and replaced about 4 out of tolerance resistors as well.
Thanks, and God bless.


http://www.nostalgiaair.org/Resources/555/M0003555.htm


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Sun 18, 2020 4:03 am 
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Location: Mountains of Mourne. Ireland.
Hello Mike, see Norm's comments here...
Crosley part number W-30321A
viewtopic.php?f=6&t=322843

Same capacitor, same location.

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If your power transformer has been replaced with a universal type, one of the low voltage filament windings may have a center tap.

Smoke is bad... :shock:
Greg.

oh... each half of the high voltage winding will read ~350V to the center tap of that winding.


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Sun 18, 2020 4:59 am 
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Fuses on the AC lines more often than not, in my experience, do not save transformer windings.

The stray wire may well not belong where you put it. The fact it has a new transformer should ring alarm bells. Does the same fault that fried the previous one, still exist & it got flipped? Whilst the majority of shorts appear within "B", I have seen plenty of shorts on the utility side, filament wires, heater wires, heaters themselves, transformers own wires and dial sockets. Wires going through chassis holes with no grommets are always a candidate for short circuits from wire cuts and beware of rubber wire tied together in looms.

It may now be a case of unloading the transformer, identifying its wires and running it unloaded to see if its cactus? Some transformers can have one single wire with no apparent ownership while all others have been accounted for. That's normally a shielded transformer and should be marked so on the schematic (not always after changes). An insulation tester is always handy. I have them one by default as its in the tube tester. The rest not related to radio directly, but needed to comply with regulatory requirements.

The idea with it is to test that no winding has gone to ground (frame), or burnt into another. There should be an inspection for obvious shorts like bits of wire cut off during refurbishment, or large blobs of solder.

Marc


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 12:18 am 
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Joined: Jan Thu 20, 2011 5:18 am
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Location: Cottage Grove Oregon; 97424
I did not say it had a new transformer, I believe it is original to the radio. I will try and run the radio with no tubes and test to see what readings I get at the various pins, ie 6 volt 5 ects.

If it still gets warm then I guess it's time for "Taps."


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 3:58 am 
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Ahh! May have confused that with another. However unloaded means unloaded and isolation means all windings floating. The tubes can stay but all wires that are not the primary are lifted as we are looking for internal shorts within the transformer and if any windings are connected to ground that is not isolated. This is also the time if you can get hold of an insulation tester, or an electrician with one at mates rates & check the insulation as described.

Marc


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 4:38 am 
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If by any chance you have powered-up any of the electrolytics incorrectly, I would discard them... at least for now!


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 6:06 am 
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egg wrote:
If by any chance you have powered-up any of the electrolytics incorrectly, I would discard them... at least for now!


+1 10Z on the back bias is a very common cap to be wrong: The Centre tap is the most negative point & the chassis is positive, relative to it.

Marc


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 7:45 pm 
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Joined: Jan Thu 20, 2011 5:18 am
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Location: Cottage Grove Oregon; 97424
I believe I have had the electrolytic s correct from the start especially 10Z as I remembered the teaching from this site that the CT is the most negative.


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Mon 19, 2020 8:11 pm 
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Location: Mountains of Mourne. Ireland.
How to Identify Amplifier Power Transformer Leads.

Image

Watch 15:43: https://www.youtube.com/watch?v=QqWM3pBirzM
fyi... a 700VCT (center tapped) high voltage winding can be written as 350 - 0 - 350

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Download video from Youtube
https://x2convert.com/LinkYoutube
360p (mp4) or 480p is good enough.
name your downloaded file to end with .mp4


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 Post subject: Re: Another Crosley 655 question and a prblem.....
PostPosted: Oct Tue 20, 2020 12:39 am 
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Joined: Jan Thu 20, 2011 5:18 am
Posts: 1454
Location: Cottage Grove Oregon; 97424
I ohmed out all the wires from the power transformer again and I noticed the insulation from one wire going to the 6F6 right as it goes through the hole in the chassis was bad at that point and could have been touching there. all the wires ohmed out good but are crusty and need to be replaced. There is some tar from the transformer where it was on the chassis but since the chassis needs de mouse pee rusting, it's a good time to pull it.


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