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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 12:58 am 
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Leigh wrote: I'll put my electronic credentials up against anybody on this board.

I bet you say that to all the boys... :wink:
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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 2:06 am 
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"Shotgunning" is more about the context. It is sometimes used in derogatory way to refer to someone just "throwing parts at it" without using any of the time honored troubleshooting or diagnostic techniques. To be fair, for the beginner this is a pretty valid approach with a high success ratio, provided they are done as noted above, one at a time. Not everyone has a wall or two of test gear and they don't want one or make a career out of it. They just want to get grampas old radio or stereo working.

Thing is when it comes to the power supply, coupling, and bypass capacitors, there isn't anything to troubleshoot. They are all shot. At least, anything made before the advent of mylar film.

And with the power supply (electrolytics) it only makes sense. By way of analogy it's asking for trouble - like "restoring" a classic car but insisting on driving around with 60 year old radial tires, radiator and fuel hoses, and blasting down the highway. Preventive maintenance means replacing those safety items before failure, before they cause further damage.

The problem with a lot of the post 60s electronic gear they started using some really proprietary parts that are completely unobtanium, unless cannibalizing another unit. The power supply is always the critical part, it is unwise to wait until it fails because it will damage other components as well.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 4:29 am 
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Mr. Detrola wrote:
Some people who aren't technically experienced don't understand that capacitors fail with age and need to be replaced. And nothing you can say to them will change their minds, until they experience a catastrophic failure caused by a part that could easily and relatively inexpensively been replaced.

Anyone who has actually serviced vintage electronics and tested those capacitors with the appropriate test equipment quickly learns that the vast majority of old paper and electrolytic capacitors are bad, to the point where it's a waste of time to even bother checking them. It's foolish to apply power to something that old until it has been properly serviced.

The problem occurs when rank amateurs think they know better than the pros who have done this for decades and learned the proper procedures decades ago.........


excellent thoughts and well put ; no truer words have been spoken ; I completely agree.

i have certainly earned the right to say that b/c experience has taught me a lot in 2 years shy of 40.

at the end of the day though, anyone can "service" their equipment how ever they choose.

steve

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 4:41 am 
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I've had a few waxies spew their guts but never had one go nuclear on me. I've acquired a few sets that had damage from firecracker caps though. These days I do the lytics and any obviously damaged caps first then go one by one. Only exception would be the Philco bakelite tubs. They get done along with the lytics.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 3:31 pm 
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Leigh wrote:
The term "shotgunning" is derogatory and totally unjustified.

It's usually used by those with minimal knowledge to describe folks with more knowledge.


What a load of crap! It 's never been used in that context. It is used to describe the wholesale replacement of components without regard to condition of the component or the set being serviced. The skill level of the technician has never been part of the definition.

sheesh ..... you are so full of yourself.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 3:35 pm 
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......locked in 3.....2.....1..........

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 5:47 pm 
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I haven't read all of the responses but I will say that I've been resistant to replacing all of the caps in my 70s vintage stereo equipment, just because there's a million caps in them and I just don't have the attention span to change them all. I have indeed replaced bad capacitors in my Lafayette amplifiers and 4 channel decoders, usually when one channel dropped out or became degraded. The good thing with stereo and quad gear, is that one can obviously trace the problem pretty quickly by comparing voltages of the sister channels. Replacing those caps have brought everything back to life. I'm sure if I did a total recap, Id be amazed at how much better each unit would sound altogether; I'll save up those projects for when I'm on vacation from work or when I retire in 22 years-if I'm lucky. I am still a strong advocate for doing complete recaps on tube stuff, as I have done. There's less capacitors and considering the high voltages, it would be silly not to.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 5:59 pm 
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DarrenWGaransi wrote:
I am still a strong advocate for doing complete recaps on tube stuff, as I have done. There's less capacitors and considering the high voltages, it would be silly not to.



Not trying to pick a fight, just trying to put some context and perspective into the discussion ....

Under what circumstances do you do a full recap? All sets, without exception, even if you don't plan to use them? All sets including the rare ones that you plan to display only? Are there any circumstances where/when you would (carefully) test a set without doing a full recap first?

I also believe that a set which will be used should be restored before use, including a full recap etc, and that is for safety's sake if nothing else. But to advocate for a wholesale recap before plugging in any set is, in my opinion, just plain foolish. Not every set will be used. Not every set is worth repairing. Some sets will be less valuable and/or historically correct once repaired and should be left alone (very few, but there are some).

So .... to each their own.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 8:21 pm 
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Leigh wrote:
I replace ALL old electrolytic and wax/paper caps.

- Leigh


As do I with a select few minor exceptions where the original filter caps showed absolutely no signs of being bad (can doesn't get hot, no excessive ripple, no hum, B+ right ETC..) where said device does not belong to someone else and is not going to be sold.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 8:28 pm 
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John Bartley wrote:
Some sets will be less valuable and/or historically correct once repaired and should be left alone (very few, but there are some).
Hi John,

I agree. I have one set that falls into that category.

Made by National, it's the first model in the series that would culminate with the HRO variants. It is the earliest known serial number for that model, so it is certainly of historical significance.

It appears to be completely original.
I would never consider changing any parts in it. It's a shelf queen.

- Leigh

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 8:34 pm 
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John Bartley wrote:
Leigh wrote:
The term "shotgunning" is derogatory and totally unjustified.

It's usually used by those with minimal knowledge to describe folks with more knowledge.


What a load of crap! It 's never been used in that context. It is used to describe the wholesale replacement of components without regard to condition of the component or the set being serviced. The skill level of the technician has never been part of the definition.

sheesh ..... you are so full of yourself.

Aww c'mon John, express how you really feel, bwahahaha!

Seriously however (yes, I do indeed have those rare moments), I too would be guilty of "shotgunning" Electrolytic's and wax caps in sets that will get used, however infrequently, and I hardly consider the term demeaning, but rather simply defining a specific technical procedure. AFA who states it, beginners or old salts, who the hell cares? :wink:

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 8:43 pm 
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In response to the original question, go watch shango066's CTC16 at MOCA series. Caps that tested good, died in service. At around (IIRC) 100 hours of operation. If he had shotgunned those lytics' he would have saved himself atleast two trips out.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sat 03, 2018 9:21 pm 
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I shotgun when it's appropriate, and I T/S when it's appropriate.

No shame in one over the other, if chosen appropriately. After all, time saved in appropriate shotgunning gives more time for problems that actually need it, IMO.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 12:32 am 
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Shotgunning is most definitely a classic derogatory term, and well deserved, expressed as scorn either towards oneself, or others. Reserved for those perceived to know only to "throw parts at a problem" until "its fixed".

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 1:11 am 
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Ok - I was going to stay out of this one, but here goes.

Here's a question I want everyone to think about. Capacitors are cheap and are usually straightforward to replace. Why not just do it while you have the set out on the bench instead of likely having to go back a couple of months or a couple of years down the road and service it again? Running an old piece of gear of any kind on old capacitors, especially electrolytics, is like driving a car with 50 year old tires. Yes, they might hold air for the moment, but the question is when, not if, they will fail.

One observation I've made over the last decade that has been increasing with frequency now. Higher voltage electrolytic caps of the 1980s are starting to fail in significant numbers. Anyone who has worked on any 1980s video arcade machines can tell you that it's become common practice to now replace all electrolytic caps in the monitor and power supply circuits simply because you want to avoid any further trouble in the foreseeable future. Most untouched machines you find in the wild now are all but guaranteed to have at least a couple of bad caps in them.

If you're concerned about originality, re-stuff the old ones. I do it all the time.

Anyone who doesn't re-cap a set they plan to use regularly is just lazy. And they will pay for it down the road.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 2:57 am 
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zenith82 wrote:
...Why not just do it while you have the set out on the bench instead of likely having to go back a couple of months or a couple of years down the road and service it again? ...


Some people have too much pride, apparently.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 3:12 am 
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Quote:
...Anyone who doesn't...is just lazy...
Careful there, I think you're getting close to the truth, but I don't make work for myself on a regular basis either. :wink:

I do change things that show signs of impending doom, but the last cap I had explode or take out other parts, like transformers for instance, was about 1962. Although YMMV, over the last twenty years or so I've had to do a second take on maybe half a dozen radios, and only one piece of test gear, a Tek 7603 PS cap. That's not to say I haven't done a couple of MASS REPLACEMENT EPISODES, but they were certainly the exception, thus, the time I've saved over the years is considerable I suspect.

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Last edited by Mikeinkcmo on Feb Sun 04, 2018 3:45 am, edited 1 time in total.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 3:45 am 
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The question was asked about powering equipment before changing caps. I often do, but in a CONTROLLED manner..

First step is a visual inspection. Obviously bare wires or burned or overheated components indicate DO NOT POWER. I also test tubes at this point to make sure nothing obvious is going to keep the radio from working.

Next I do a resistance check of B+ or other supply circuits to find any shorts. If none are obvious I power the radio using a current limited variac supply set at what ever the draw of the radio is plus 10 percent. Rectifiers or transformers should be able to survive a 10 percent overload for the few milliseconds it takes for the limiter to trip power. If they can't, likely they were on their way out anyway. Besides, since the voltage is brought up slow and monitored for irregularities while this is done, likely a problem will show itself long before anything reaches the design limits. If the power transformer is questionable, this is where I would do an unloaded test of it by pulling the rectifier and bringing up AC. The transformer should operate at full voltage several minutes and not overheat since the only load is the tube heaters at this point. If that is good I reinstall the rectiifier then repeat the slow power up

Once I get up to 80% or so of supply voltage the radio should show some signs of life. Most filter caps fail open so hum is not really an issue at this point; all O want to see f there is no failure of some unobtainium that makes further work a waste of time.

If things look hopeful at this point I power down, change the filter caps and any paper caps that are in voltage critical areas (coupling caps on output, tone caps on plate circuits, etc.) From here it becomes a matter of testing and replacing other components, but at least I know the project stands a good chance of success rather than wasting time changing a lot of caps only to find the power transformer or some special component is also bad. In the end though, the radio will have had most caps changed as well as any out of spec resistors or other components that show signs of problems.


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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 6:09 am 
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It depends on how "shotgunning": is used. At Xerox we had a few models that didn't live up to engineering expectations so to say, with
some the plan going in was to shotgun the call and replace all the boards and modules, which was funded for a while on some lemons, I mean models...

Then there is the guy who can't troubleshoot and shotguns every call, looks up an error code before going, ordering a pile of parts to take in.
I can tell you all after running several mid-volume workgroups, the highest part spenders were the worst trouble shooters, every time.

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 Post subject: Re: Public obsession with replacing capacitors
PostPosted: Feb Sun 04, 2018 10:38 am 
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Eh eh, what do you call a "tech" :roll: who can't trouble shoot to component level?

A board swapper.

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