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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 12:33 am 
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Location: Arlington, TX, USA
I have to wonder just how many radios have been damaged to the point of unrepairability due to being powered up with original, possibly defective parts still in place. So far I haven't had anything like that happen to me, although I don't do as much radio work as others here. Normally either there is a loud hum in which case I shut it off, or it works weakly or not at all if there is a problem. I have two radios here right now which are on most if not all their original parts and they operate normally, at least at this time. One is a Philco 46-1213 which has about 50 or so paper capacitors and outside of the one I replaced trying to get the FM to sound better (it was actually a factory wiring error instead) and one obviously bad electrolytic is on all the original parts and operates normally, no obvious distortion or other problems, even when running for hours at a time. The other is a 1948 RCA portable (4 tubes plus rectifier) that I got in a box lot at the radio club auction last weekend. It had a piece of tape on the side saying "works", so I plugged it in, and it really did work quite well. Clear sound and no hum to speak of, and I ran it for hours as well. I thought someone just had to have serviced it to work so well, so I took it apart to look. No, it's 100% original on the inside including the tubes! These two radios are going to stay this way until they don't work properly anymore at which time I will repair them. Also, I am repairing a 1939 RCA table radio for a friend. The paper capacitors were all bad in that one; the leads just fell out of the capacitor bodies. But the electrolytic was still good. I restuffed that one anyway since it was going to someone else besides me and I want it to stay working.

There seems to be a belief among the vintage audio crowd that any old piece of audio equipment needs all the electrolytics replaced to work properly. I have done this myself in the past and the results range from a slight improvement to no difference at all, at least when starting with a normally operating unit; no obvious problems like hum or low signal level beforehand. There might be some improvement from replacing power supply filter capacitors that have more ESR than a modern replacement, but in the signal path I doubt there is much room for improvement unless there is something really wrong with a particular capacitor.

I personally try to see how the radio performs before any parts replacement or troubleshooting so I know what I am starting with, at least if it looks safe to do so upon a visual inspection. I do realize however that there are those who do not have much experience with electronics who might leave something powered up that needs to be shut down instead. The "recap before plugging in" advice is probably useful in that case.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 12:57 am 
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I have not yet read all replies on this thread; but, here's my position on capacitor replacement.

Yes, I agree that electrolytic and paper capacitors should be replaced in equipment that was made in the 1960's, or earlier. However, simply replacing the capacitors will often not magically bring the equipment back to like new performance. Over the years, I've known of people who were very good at changing capacitors; but, knew zip about troubleshooting or circuit theory. When they replaced all the capacitors and the equipment still didn't spring to life, they were lost and the equipment usually went on the shelf until they got tired of looking at it. That's why I urge anybody who is going to be servicing vintage equipment to at least get some basic test equipment and learn some basic troubleshooting skills.

OTOH, I've known people who were too cheap to replace old capacitors and they'd do just enough to get the equipment working. Then, they'd put the equipment off on somebody else and then one of the old capacitors would fail.

As far as 1970's and later equipment, I replace capacitors on a "need to replace" basis. A while back, someone on one of the Facebook TV groups was talking about re-capping a late '80's solid state TV and I told them that if they wanted to do that, it was certainly their business; but, all they'd be doing is wasting a lot of time and money. On the rare occasion that I'm asked to fix an '80's or later TV, the only capacitors I change are those that need changing and I'll sometimes replace a few capacitors that I know have a high failure rate.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 8:00 pm 
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Erich Loepke wrote:
There seems to be a belief among the vintage audio crowd that any old piece of audio equipment needs all the electrolytics replaced to work properly. I have done this myself in the past and the results range from a slight improvement to no difference at all, at least when starting with a normally operating unit; no obvious problems like hum or low signal level beforehand. There might be some improvement from replacing power supply filter capacitors that have more ESR than a modern replacement, but in the signal path I doubt there is much room for improvement unless there is something really wrong with a particular capacitor.


I can agree that you may or may not notice immediate improvement. The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road. It should avoid having to open up the radio now and then to troubleshoot it and replace one or two parts. Tubes excluded. Unless of course someone likes to do this.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 9:05 pm 
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Tbone wrote:
The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road.

Exactly!

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 9:26 pm 
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Here ya go guys..


Attachments:
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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 9:54 pm 
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Tbone wrote:
The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road.
Precisely. Reliability is a primary goal of any restoration

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 10:38 pm 
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Leigh wrote:
Tbone wrote:
The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road.
Precisely. Reliability is a primary goal of any restoration

- Leigh


Leigh is speaking only from an electronic perspective. If we were speaking from an historical perspective we might either not replace the components and tag the set "not for use" or we might use replica parts so as to maintain a visually correct appearance. It depends on how accurate we wish the restoration to be.

After all, one of the definitions of the word "restoration" is :

Quote:
the process of repairing or renovating a building, work of art, vehicle, etc., so as to restore it to its original condition.
plural noun: restorations
"the altar paintings seem in need of restoration"
synonyms: repair, repairing, fixing, mending, refurbishment, reconditioning, rehabilitation, rebuilding, reconstruction, overhaul, redevelopment, renovation; informalrehab
"the restoration of derelict housing"


... stir, stir, stir .... :wink:


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 10:56 pm 
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John Bartley wrote:
Leigh wrote:
Tbone wrote:
The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road.
Precisely. Reliability is a primary goal of any restoration
- Leigh
Leigh is speaking only from an electronic perspective. If we were speaking from an historical perspective we might either not replace the components and tag the set "not for use" or we might use replica parts so as to maintain a visually correct appearance. It depends on how accurate we wish the restoration to be.
That's true.

I have a National receiver that's the first model in the family that would become the HRO.
It is the earliest known serial number of that model, so definitely of historic significance.

It appears to be all original and complete.
I would never consider replacing any parts in that set.
Nor would I try to power it up.

There are certainly situations where cosmetic-only restorations are appropriate.

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 11:32 pm 
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Location: Arlington, TX, USA
Tbone wrote:
Erich Loepke wrote:
There seems to be a belief among the vintage audio crowd that any old piece of audio equipment needs all the electrolytics replaced to work properly. I have done this myself in the past and the results range from a slight improvement to no difference at all, at least when starting with a normally operating unit; no obvious problems like hum or low signal level beforehand. There might be some improvement from replacing power supply filter capacitors that have more ESR than a modern replacement, but in the signal path I doubt there is much room for improvement unless there is something really wrong with a particular capacitor.


I can agree that you may or may not notice immediate improvement. The idea of replacing the capacitors and high failure rate components is to make the equipment reliable for years down the road. It should avoid having to open up the radio now and then to troubleshoot it and replace one or two parts. Tubes excluded. Unless of course someone likes to do this.


If only that were the reason given for recapping a 1970s solid state amplifier/receiver. What I usually noticed is that the recapping was being done for audiophoolish reasons of sound quality "improvement". If I am doing work for a paying customer then I will be replacing those capacitors which can fail later on.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 11:38 pm 
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John Bartley wrote:

After all, one of the definitions of the word "restoration" is :

Quote:
the process of repairing or renovating a building, work of art, vehicle, etc., so as to restore it to its original condition.
plural noun: restorations
"the altar paintings seem in need of restoration"
synonyms:................refurbishment.......


... stir, stir, stir .... :wink:

Yup, and you are good at stirring, eh eh!

Quote:
The refurbishment of something is the act or process of cleaning it, decorating it, and providing it with new equipment or facilities.

https://www.collinsdictionary.com/dicti ... urbishment

So how do you reconcile that? :wink:

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Wed 28, 2018 11:46 pm 
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fifties wrote:

Quote:
The refurbishment of something is the act or process of cleaning it, decorating it, and providing it with new equipment or facilities.

https://www.collinsdictionary.com/dicti ... urbishment

So how do you reconcile that? :wink:


Ahhhh whuddya expect from a dictionary that uses colloquialisms stripped from computer databases as definitions. I mean ... really! :roll:


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Thu 29, 2018 12:41 am 
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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Thu 29, 2018 2:45 am 
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Anybody know what this is?

Image

And how is it one knows where on their newest victim lies?

Where is it that the new "increased reliability" factor begins to dominate?

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Fri 30, 2018 1:48 am 
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Quote:
Anybody know what this is?

I'm guessing, some kind of Marriage Longevity Calculator ? :roll:

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Fri 30, 2018 2:20 pm 
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Barry H Bennett wrote:
Quote:
Anybody know what this is?

I'm guessing, some kind of Marriage Longevity Calculator ? :roll:

Me thinks you may be correct. :wink:

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Fri 30, 2018 3:13 pm 
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After reading all these pages, I think I'll stick with my 20's battery radios. Check tubes, grid leak, wiring, transformers and power it up. Mica caps almost never fail and it's hard to smoke anything at .25 amps. Far less stressful. :wink:

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Fri 30, 2018 5:05 pm 
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Leigh's radio is one example of something where keeping all of the old parts may be justified. For more common radios, we all need to remember that many hundreds of millions of the old capacitors and resistors were made, many still exist, and documentation on them is extensive, so no history is being lost by using modern parts to restore/refurbish such a radio.

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