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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Sun 25, 2018 11:19 pm 
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John Bartley wrote:
Does everyone who is preaching wholesale cap replacement before ever firing up a radio .... also change them in:

radios that are not going to be used regularly?
radios that are old enough to be unique and should go to a museum?
radios that might already have something wrong with them that might make them not economical to fix?
radios that you have two of and plan to make one from .... but ya' gotta' see which one is the donor and which one to fix?

Or .... do you sometimes turn on a set that isn't (horrors!) shotgunned?

Despite trying to scare newbies with stories of failed caps taking out transformers etc .... how many of you have actually seen a radio fail expensively during a quick power up test run? ..... sure it happens, but .... probably to very few of you and of those few it was probably a microscopically small percentage of the sets you've powered up.

Instead of preaching gloom, doom and failure, why not teach how to do a safe power up and trouble shoot? Why not use the tools of your trade?

I am in favour of the "safe startup", then troubleshoot to determine whether or not to repair and/or restore.



John, I've posted before that I'll power up an AA5/6 initially for a minute, just to see in what state it's in; working, humming, no sound. Then I'll change the Electrolytics and power it up again. I don't have a Variac, but do use an ISO. I've been criticized on this board for leading newbies down a dangerous path by suggesting my method, so ya can't totally win here.

Now that said, and to address your points, I believe that this, being a hobbyist, rather than a conservators site, would favor replacing components as needed, of course meaning all Electrolytic's and wax/paper caps, in order to get the set working again.

Hell, I've got table sets that I worked on 15 years ago that haven't been used since, but the point is that I have NP firing any of them up again, because I know they've been restored.

AFA not being economical to fix, or using two to make one, what kinda money are we talking about for 2-3 filter caps and a half dozen yellow axial film caps? I think most of our members enjoy getting a circuit, no matter how grungy, to work.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 12:19 am 
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+1 to what Leigh said a few posts above. Safety first, and then the approach one takes with a nonfunctional radio is going to be somewhat dependent on whether one is a repairman, a collector, a buyer and seller on eBay, a hobbyist, a tinkerer, a person who simply wants a shelf queen, someone who wants a radio for daily use, etc. I do sense we all agree that it is foolhardy to power up a radio that hasn't been turned on for years, without first doing some basic tests and lacking any knowledge of what could happen when components see voltage or current for the first time in decades.

Bryan


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 12:55 am 
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John Bartley wrote:
Despite trying to scare newbies with stories of failed caps taking out transformers etc .... how many of you have actually seen a radio fail expensively during a quick power up test run? ..... sure it happens, but .... probably to very few of you and of those few it was probably a microscopically small percentage of the sets you've powered up.

Instead of preaching gloom, doom and failure, why not teach how to do a safe power up and trouble shoot? Why not use the tools of your trade?

I am in favour of the "safe startup", then troubleshoot to determine whether or not to repair and/or restore.


Amen John. I'll change them in due time but I strongly disagree (as an earlier poster stated) electrolytics are "guaranteed to be bad." That's nonsense. I've judiciously powered up many radios with old
caps and either nothing happened except hum or they worked just fine. I'm not a renegade but neither am I an old lady who's waving hands around in the air.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 1:13 am 
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Tbone wrote:
I want to do the best job possible so I don’t have to revisit it later. .


amen, absolutely amen

steve

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 1:16 am 
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I worked in a car radio shop back in the late '70s. I did mostly factory transistor radios.

My boss, did several old tube car radios. Even back them he replaced all paper caps as most were bad. However as the radios were to be "all original" and had obtained many NOS paper caps. This was south Fla and the high heat and humidity almost guaranteed leaky caps.

I replace all grid isolation caps and all power supply caps as a short would do damage. Then I may power up to do basic tests. I'll still replace all paper caps. Biggest problem is a a leaky grid cap would likely burn out an IF transformer in the next stage.

If the radio was to be "as original as possible", I'd re-stuff paper caps.

I have a MIG wire feeder built in the early '70s. I just wanted to get it going. It had molded caps in the supply. I powered it up and was testing it with the cover open. Was working on the rest of the system with it powered on. I heard a loud bang and looked to see a mushroom cloud appear above the feeder. One of the molded caps had exploded. Luckily it did not damage the PCB or the rare SCR's.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 2:33 am 
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FStephenMasek wrote:
I finally stopped checking resistors, except out of curiosity. Somebody here mentioned that the modern ones are more stable, something which matters more in the RF sections. Now, I just replace all of them while I'm busy replacing capacitors, especially since there is usually a need to de-solder at least one end of each to replace a capacitor or wire.


Agreed.

I use 1% metal film resistors when possible as they are mostly under $1 each.

The main reason is when I fix something I don't want to have to disassemble it every so often only to find an out of tolerance original resistor was the problem.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 2:49 am 
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John Bartley wrote:
Instead of preaching gloom, doom and failure, why not teach how to do a safe power up and trouble shoot? Why not use the tools of your trade?

Nobody is preaching gloom and doom.

My advice about replacing capacitors is based on decades of experience fixing radios.

I started fixing radios when I was 7 years old, and was being paid to fix them when I was 9.

That was way back in the 1950s, when many of our "vintage" sets were current production.

Over the years, the ratio of bad capacitors to good capacitors has increased to the point that most of them are bad, and need to be replaced.

I value my time, regardless of whether or not I'm being paid to fix a set. I take pride in my work, expecting sets I repair to be functional long after I no longer am.

If your time is worth zero, or you don't care about reliability, then I encourage you to power up the radio after every component replacement.

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:12 am 
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Leigh wrote:
I value my time, regardless of whether or not I'm being paid to fix a set. I take pride in my work, expecting sets I repair to be functional long after I no longer am.

- Leigh


i feel the exact same way. i have no time to "tinker", "play", or "mess around" during a repair or restoration, much less AFTER it has been "restored/repaired". the job is done nicely, neatly, and properly the first time.

anyone can "restore" their radios however they want. they can go against the advice that is always given on this board (especially about capacitors) and plug them in barn fresh if they want and let the smoke out, it matters not to me.

my methods, as described above, have proven to yield an excellent and top notch working and performing set now and for years to come.

i have never and will never fry a set due to an old 39 cent to 2 dollar capacitor.

steve

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Last edited by Dutch Rabbit on Mar Mon 26, 2018 3:42 am, edited 1 time in total.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:36 am 
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Leigh wrote:

If your time is worth zero, or you don't care about reliability, then I encourage you to power up the radio after every component replacement.

- Leigh

That's kinda harsh, and I haven't seen anyone advocate firing a set up after every single component replacement.

Personally, I'll change out the Electrolytics, try the set for a minute, then replace the wax caps 2-3 at a time, check, etc. So the radio chassis gets energized 3-4 times in maybe an hour, and this way if I screw up and mis wire a cap, which I HAVE DONE, the research and repair time is limited to the last two or three I had replaced. Seems a good way to reduce over all repair time.

Oh yeah, and I've been working on radio's, on and off, since 1956. Learned a little bit in 62 years...

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:40 am 
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I understand the point about learning. However, I find that I learn the most from working sets.

With apparati where there are parts I know that I am going to replace, I do not spend time doing anything with power on. When it comes time for trouble-shooting, I want to start with a short list of possible issues. A 2% chance of a bad cap taking out another component is too high. My OCD approach takes enough time as it is---why do I want to add to the workload?

I am considering an exception: Check for SMD after re-capping and first power-up. I did not enjoy tearing into a suspect transformer--suspect because the other similar one HAD the issue---only to discover it was fine.

To me, the secret is a complete check of coils, transformers, and any other non-generic part, followed by a "shotgun" replacement of all suspect parts. I do not shotgun resistors for the simple reason that they do not normally cause failure of other parts, and I think it's better to see the key voltages first.

If a non-generic part is bad, that gets fixed first---or the set goes on the shelf until the part is found. I cringe when I read about someone recapping a set, finding it doesn't work, and then discovering a bad RF coil or worse.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:45 am 
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fifties wrote:
Oh yeah, and I've been working on radio's, on and off, since 1956. Learned a little bit in 62 years...

And that's the critical difference between your procedure and what we recommend to newbies.

You're like me, having started back when most of these capacitors were good. You fired up a set (on a Variac), located the bad component, replaced it, and you were done.

Over the years you found more and more bad parts, and learned how to recognize the symptoms before any serious damage was done.

Unfortunately, we can't teach experience. That's something each person must learn.
That's why we formulate the recommended procedures such that damage is avoided.

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:50 am 
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And that's the critical difference between your procedure and what we recommend to newbies.

In fairness, there are quite a few experienced people here that use Richard's approach.....

Follow the universal truth: If it works, it's OK.....

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 1:19 pm 
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My only criticism of shotgunning capacitors is the potential for a inexperienced technician to make an error during the process, and frustration when his restored radio does not work when its completed.

With experience and knowledge, the potential of this happening is much lower.

For the beginning collector/restorer, I suggest replacing only the capacitors that have the potential to damage a set or present a safety hazard. Also check transformers and non-generic parts to ensure they are good. Then apply power at reduced voltage and confirm whether the radio works or not.

At that point, replacing the remaining caps one or two at a time allows enables a beginner to avoid a mistake in wiring and not knowing where or when it happened.

For experienced technicians, none of this applies. Shotgun to your hearts delight.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 1:24 pm 
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processhead wrote:
My only criticism of shotgunning capacitors is the potential for a inexperienced technician to make an error during the process, and frustration when his restored radio does not work when its completed.


That can happen if the inexperienced tech disconencts more than one component at a time.

Even us experienced techs can sometimes make a mistake unless we remove one component at a time.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 1:36 pm 
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I think if you take the time to read what I wrote and what I have always written, you won't see me saying to always power up after each component (even though it's not a bad idea and a good work check for a newbie until they get comfortable doing repairs). You also won't see me saying not to completely recap.

What you will see me saying is that not every set is a "full restore" set. Not every set is worth fixing. Some sets have different intended purposes. Some sets have different values. Some sets have different levels of rareness. NOt all sets are the same or are intended for the same purpose.

All I have ever advised is :

Assess first safely
Having assessed ... make a decision about how far to restore
If safety of any kind (human, the set) is needed for a radio to be a daily player, then do that ... including replace any and all parts that may fail.

Advising people to completely and fully recap every set they get before they ever plug it in is detrimental to the hobby and to the learning process. It teaches nothing about either the technology or about how to go thru' an assessment and decision making process.

You may have a different opinion. You are welcome to it.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 2:50 pm 
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John Bartley wrote:
What you will see me saying is that not every set is a "full restore" set. Not every set is worth fixing. Some sets have different intended purposes. Some sets have different values. Some sets have different levels of rareness. NOt all sets are the same or are intended for the same purpose.


In my opinion

Yes sets such as those beyond hope indeed should not be restored. The rest if the intent is to use the radio at all should be fully restored.

John Bartley wrote:
Advising people to completely and fully recap every set they get before they ever plug it in is detrimental to the hobby and to the learning process. It teaches nothing about either the technology or about how to go thru' an assessment and decision making process.


Respectfully disagree.

One can still learn plenty as a simple recap and re-resistor may not always restore a set to proper operation.

It is the more experienced techs who can plug in the radio without recapping or after every few caps because the experienced tech knows what caps may be ok to leave in circuit for an initial test and what caps should be replaced first.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 3:14 pm 
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Wow,.. I mean Wow.. Hi I'm Stan, and Well, I'm a shot-gunner.. :o
I cut the cord off first thing.. Most times they have bare spots and its just common sense.. And then there is always the possibility that the radio has been "worked" on at some point in the past.. So I am going to study the heck out of a schematic, and go over everything with a fine tooth comb.. To me, with exception to micas, a complete recap is a good "cheap" opportunity to eliminate some problems from the start.. By the time I get finished I am very familiar with the radio and have a good idea where to look if something does not go well.. Radio theory may go right over my head, but I have a whole wall full(and some floor space) of old timers that now work.. What does it matter how you get there, as long as you have fun (and don't die) doing it..

Stan

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 4:51 pm 
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Too many replies to read so, this may have been mentioned already. Leakage in an old paper capacitor increases greatly as the radio warms up. if measuring the leakage, best to give it a shot with the heatgun.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 5:36 pm 
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pixellany wrote:
Quote:
And that's the critical difference between your procedure and what we recommend to newbies.

In fairness, there are quite a few experienced people here that use Richard's approach.....

Absolutely true. I do not disagree with it nor criticize it... for them.

But there's no way you can teach experience to a newbie.

You teach them rules that will accomplish the task without endangering them or their gear.

Once they develop familiarity with the environment, they will experiment.

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Mar Mon 26, 2018 5:52 pm 
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John Bartley wrote:
Advising people to completely and fully recap every set they get before they ever plug it in is detrimental to the hobby and to the learning process. It teaches nothing about either the technology or about how to go thru' an assessment and decision making process.......

This is an important point---but I think mostly applicable to beginners.

I honestly don't know the best way to teach this stuff.....many of learned through some kind of chaotic process over a period of years or decades. One of my sometime "soap box moments" has to do with following the current paths and understanding the voltage changes along the way. I was tuned into the concept around age 10 or so, and I'm not quite sure how I learned it. At another extreme, we sometimes encounter people past retirement that struggle with the concepts.

Everyone here that makes a good-faith attempt to provide help makes some kind of assumptions about the recipient's skill level. In the best case, we learn about the person before giving advice but---as a minimum--we rely on people to tell US when they do not understand something.

As a teenager, I learned how to replace parts--one at a time--based on some combination of guesswork and actual trouble-shooting. A lot of the advice I got was akin to the popular advice given for cars: "replace the points and condensor"----In almost all cases, this came from an individual who had zero clue how the Kettering Ignition worked. Condensors in a radio: If there is hum or smoke, replace them.

After building, repairing, and refurbishing a lot of electrical apparati over a period of 50+ years, I learned to be a "shotgunner" to at least some degree. With a tube set that is older than I am, it's easy. I don't get lost in the circuits, and I check everything against the schematics before applying power. I don't wast time testing capacitors, since I know they are bad--or will be soon. I sample a few resistors, but mostly don't worry about them until I'm ready to check voltages.

A crucial first step is the inspection, inclucing DC resistance checks on all proprietary components, inspection for damage, overheating, or prior visits by unskilled hands. Maybe 5% of the time, the inspection suggests a total teardown as the best strategy. As a minimum, some disassembly is almost always indicated, and this--in turn--affects the strategy for specific components.
The concise term here is Make a Plan.

Perhaps the best thing we can do for newbies is to walk through a few basic concepts and strategies, and then see what kinds of questions come back.

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