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Author Topic: How hot does a Boat Anchor get?  (Read 40733 times)
KG8LB
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« Reply #30 on: February 05, 2015, 05:54:43 AM »

   Manufacturers of electrical components typically de-rate components as operating temperatures are increased . They do this for many very good reasons .
   Insulation breakdown voltages drop as temeratures rise , resistors change more rapidly as temps increase . Transformer winding insulation on older transformers is degraded and it's life shortened by elevated temperatures .  Not an opinion , a recognized fact .

 Not in the least advocating hanging biscuit fans all over every piece of gear . However , getting back to my first posting there are some opportunities to improve cooling as well as component life with simple changes that promote better airflow to critical areas . Passive , convection current cooling can be very effective indeed .   https://microphoneprojects.shutterfly.com/pictures/11
  
 Glass envelope power tubes like the 3-500z anode seals fail when deprived of proper cooling .

  Yes , the statement "If it's a "boat anchor" then it isn't dead.  Heat never killed it."

As an absolute is indeed a flawed assumption .  I have replaced a lot of parts that would have functioned far longer and likely would not yet have failed at lower temperatures .   The manufacturers of components such as electrolytic capacitors realize this and readily admit it .
 
« Last Edit: February 05, 2015, 06:18:54 AM by KG8LB » Logged
W8JI
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« Reply #31 on: February 05, 2015, 03:15:43 PM »

Oddly, the dozens and dozens of radios I have in my possession do not have that problem.

I guess, like K8AXW, my experience is different than just lifting data out of context and making it a rule.
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KD0ILM
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« Reply #32 on: February 05, 2015, 04:40:27 PM »

I would agree that that most if not all reputable Ham radios were built to operate in their natural conditions. Convective cooling works well where it was designed to do so, amps have all different kind of systems that work.

Heathkits are said to have carbon composition resistors that age (general up) and need replacing. This is true of all or most 30 or more year old carbon resistors. I remain surprised at how many of them are still good when checked with good equipment. When I tear into one I general don't find more than 30% of them beyond my replacement criteria. Most of them are specced at 10% and I stick with 5%. Most are within that spec. I am not going to be around to discover if the new carbon film resistors I am installing will last at least that long. All this with standard cooling.

My questions about what temperatures they generally run at was only to get a baseline so I could buy the correct temperature measuring equipment. The rest of it is just for fun. I am not trying to reinvent the wheel or improve something that may not need fixing. I am just looking for something to play with while listening to nets, working digital or calling CQ on a quiet band.

I am working at rebuilding an SB-301 and 401 receiver and transmitter and also want to see if I can get away with stacking them. I am short on space and it would not be my normal choice.
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K1DA
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« Reply #33 on: February 05, 2015, 06:36:44 PM »

The audio amp in the 75S series runs hot enough to fry an egg, but the tubes last a long time.
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KG8LB
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« Reply #34 on: February 06, 2015, 04:54:03 AM »

Oddly, the dozens and dozens of radios I have in my possession do not have that problem.

I guess, like K8AXW, my experience is different than just lifting data out of context and making it a rule.

   What problem ?  
Who has lifted anything from context and made a rule ?  The strawman approach doesn't really cut it .
Again :
  Not in the least advocating hanging biscuit fans all over every piece of gear . However , getting back to my first posting there are some opportunities to improve cooling as well as component life with simple changes that promote better airflow to critical areas . Passive , convection current cooling can be very effective indeed .   https://microphoneprojects.shutterfly.com/pictures/11
 What rule ?


  The shotgun approach of drilling thousands of holes in an attempt to secure cooling is often less effective than placing intake and exhaust vents strategically to promote convection cooling .  It may be ok for bragging rights but to some it looks pretty lame .
 The typical "amateur" swiss cheesing can actually impede cooling .

    To state that certain components last longer when run at lower temperature is a fact . Read the data on electronic component testing . The life of many components is a direct inverse proportion to the operating temperature .

   Good design will place temerature sensitve components away from heat producing components when possible .

   So little time to put any real use to dozens and dozens of radios anyhow ....

The audio amp in the 75S series runs hot enough to fry an egg, but the tubes last a long time.

   The tube is not the real issue . Take an application where the hot running tube is mounted horizontally , place a couple of 85 degree C electrolytic cans directly above it and their life expectency will plummet . 
Reverse the situation , place the caps below the tube , add a reflective baffle and the average cap life will be extended significantly .

   Illinois Capacitor ratings for aluminum electrolytics run like this :  Take a  450 volt electrolytic with a life rating of 500 and a 85Deg C temp rating . Operating at85 deg ambient , the projected life is 563 hours . Drop the ambient temp to 70 degrees and the life extends to 1,591 hours , nearly tripled the life !

    
« Last Edit: February 06, 2015, 05:57:08 AM by KG8LB » Logged
W8JI
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« Reply #35 on: February 06, 2015, 11:42:04 AM »

The audio amp in the 75S series runs hot enough to fry an egg, but the tubes last a long time.

That's because the temperature inside the tube doesn't change as radically as temperature outside, and it is designed to run hot.

Look at MTBF on electrolytic caps.   Data is often extracted from context of a large process, and used to come up with a claim a temperature reduction of xx degrees will make the life go from Y hours to Z hours.

As amateurs, we don't operate out equipment in CCS service. Most components in amateur service relate more to shelf life and off-and-on cycles, or abuse, than operational life. Some things, like many Chinese tube types, only have hours of life no matter how they are operated. While most old quality tubes might have 5,000 or 10,000 hours of operation in conservative CCS operation, some tube types fail in 100 hours or less just by running the filament at 90% voltage without any emission current or thermal cycling.

To decide if a lower cabinet temperature would actually change anything, we would have to look at what failed and why it failed.

Nearly all of the old radios I have have capacitor failures just because of age. The equipment spends 90% or more of its life off, just sitting a shelf. Resistors age from moisture ingress, capacitor seals dry out, wax cracks, materials inside corrode; the list goes on and on.

I got a Globe Scout 65A down off the shelf in a dry storage building the other day, for example. It has one of the worse cabinets for ventilation, and component voltages are all over the place. It had original electrolytics, tubes, and most other parts. I've owned it for maybe 30 years, and that entire time it sat unused. (I have many amplifiers and radios like that, some dating back to the 1910's.)

I plugged it in, tuned it on, and it ran. The only issue making it unusable was the filter capacitor lost capacitance. This is an early or mid 1950's capacitor. I doubt reducing cabinet heat would make a 60 year old paste-electrolyte capacitor live longer in something that spends most of its life sitting cold.

The common issue people really have with old radios not working is the radios are old. If they had thermal issues noticeably shortening life, they would not be loaded with OEM parts. If heat on wires was an issue, the wires would have dried out years ago.

I can replace the electrolyics in that supply, and the Scout will be good for the shelf life of the new caps. If I put a 100 CFM fan on it, the parts inside will last around the shelf life of the parts even if I operated it as a main radio.

Now if it was at a BC station and ran 24/7, I'd worry about heat and component headroom. Many parts would not make it to expected shelf life.
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N3QE
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« Reply #36 on: February 06, 2015, 12:22:15 PM »

In the wintertime in a cold shack, a HW-101 is "nicely and comfy warm" in the shack while operating, not much above body temperature.

If it's 90 degrees ambient in the summertime, the HW-101 cabinet can get almost too hot to comfortably touch (130F-140F). At the same time, any dark car outside in the sun is way hotter!!!
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W1BR
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« Reply #37 on: February 06, 2015, 01:57:31 PM »

Many older boat anchors benefit from running at reduced input voltage. Dropping from 125 to 115 VAC often makes a substantial difference in boat anchor temperatures, esp. the power transformer cores, without resorting to external cooling devices.  Anyone who believes that the organic based insulation used in vintage transformers benefits from being running hot should invest in some bridges that I have for sale. Those radios were designed to be produced as cheaply as economically possible. After 50 or 60 years, parts will be deteriorating or failing. There are a lot of dead boatanchors with destroyed power transformers floating around. I'd rather keep mine running properly, for my use, and for the next guy down the road.

Pete
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KG8LB
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« Reply #38 on: February 06, 2015, 03:38:15 PM »

Many older boat anchors benefit from running at reduced input voltage. Dropping from 125 to 115 VAC often makes a substantial difference in boat anchor temperatures, esp. the power transformer cores, without resorting to external cooling devices.  Anyone who believes that the organic based insulation used in vintage transformers benefits from being running hot should invest in some bridges that I have for sale. Those radios were designed to be produced as cheaply as economically possible. After 50 or 60 years, parts will be deteriorating or failing. There are a lot of dead boatanchors with destroyed power transformers floating around. I'd rather keep mine running properly, for my use, and for the next guy down the road.

Pete

  Good points , all . In fact some of us do use our radios and there is certainly no harm done by taking measures to ease the temperature strains in some of the higher power stages . Anecdotes of radios that are seldom used have little bearing on the hard fact that elevated temperatures do indeed measurably shorten the working life of many components . 
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KK5DR
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« Reply #39 on: February 08, 2015, 08:19:09 AM »

It's not important how hot the box gets. It's more important that individual tubes not get too hot. Temp specs have been published for each tube. Easy enough to find the data and measure the tubes.
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W1BR
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« Reply #40 on: February 08, 2015, 08:37:58 AM »



I can replace the electrolyics in that supply, and the Scout will be good for the shelf life of the new caps. If I put a 100 CFM fan on it, the parts inside will last around the shelf life of the parts even if I operated it as a main radio.

Now if it was at a BC station and ran 24/7, I'd worry about heat and component headroom. Many parts would not make it to expected shelf life.

Electrolytic capacitor life is generally based on ripple current and temperature. The manufacturers' data sheets provide that data. A cap run at maximum ratings may have a rated life of only 1000 hours.  You can't make generic statements as fact based on anecdotal person experiences. Besides, many hams are shopping for cheap Chinese crap parts on eBay, instead of ordering from reliable US distributors.  I note that your website has a section devoted to undue transformer duress caused by the increased peak repetitive charging currents caused by replacement silicon rectifiers. Same goes for reducing the AC line voltages. The transformer runs cooler. That is something that can be measured, and shown.
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W8JI
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« Reply #41 on: February 09, 2015, 03:45:53 AM »



I can replace the electrolyics in that supply, and the Scout will be good for the shelf life of the new caps. If I put a 100 CFM fan on it, the parts inside will last around the shelf life of the parts even if I operated it as a main radio.

Now if it was at a BC station and ran 24/7, I'd worry about heat and component headroom. Many parts would not make it to expected shelf life.

Electrolytic capacitor life is generally based on ripple current and temperature. The manufacturers' data sheets provide that data. A cap run at maximum ratings may have a rated life of only 1000 hours.  You can't make generic statements as fact based on anecdotal person experiences. Besides, many hams are shopping for cheap Chinese crap parts on eBay, instead of ordering from reliable US distributors.  I note that your website has a section devoted to undue transformer duress caused by the increased peak repetitive charging currents caused by replacement silicon rectifiers. Same goes for reducing the AC line voltages. The transformer runs cooler. That is something that can be measured, and shown.

That is a worse generalization than anything.

1.) A transformer's expected life has little change unless it goes over some failure rating. It is not remotely close to a linear curve or straight line with temperature. If you get close to insulation thermal ratings, it is a problem. If the transformer is well away from limits, it doesn't matter how hot it is run.

2.) I see many people who think the little hour numbers on a capacitor's case directly mean something. There is a rather complex estimated life calculation that has to be used, and most capacitors (even at 75C) last many thousands of running hours. In amateur service, unless sometime very serious is wrong, shelf life and just the chance of getting a bad part generally become the dominate players.

It's difficult for me to put this in words, but there is a common tendency (that I can't quite understand) to lift a single fact from a bunch of complex data and extrapolate it into a universal law that has nothing to do with the original fact.

We get goofy stuff rules like "If you make the radio run cooler it will last longer" because somewhere there is a complex formula for MTBF that shows increased temperature decreases life.

I'm sure there is a name for the tendency to extracting a single truth from a complex behavior and making that single thing some sort of unlikely generalized rule.  I don't know what it is, but it sure happens a lot.

I see very few old radios that have heat-related component failures. The primary issues I see, and I have dozens of pieces of old junk, are related to age and storage humidity. If they were run at 50F or 150F internally up where the tubes heat things, they would be in same general shape.

Another case in point. There is a thread in this forum about resistors going bad. The normal carbon resistor aging from elevated temperature is a decrease in resistance. The normal carbon aging from humidity is an increase in resistance. Look at which of the two most people report in that thread. Since almost all increased resistance failures are related to humidity, I could make a silly argument if people ran the resistors warmer to keep them dry, they would still be good. The real issue is the age and humidity. The same is true with many other component failures in old rigs.

 

« Last Edit: February 09, 2015, 04:06:41 AM by W8JI » Logged
W1BR
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« Reply #42 on: February 09, 2015, 04:05:37 AM »

I got a Globe Scout 65A down off the shelf in a dry storage building the other day, for example. It has one of the worse cabinets for ventilation, and component voltages are all over the place. It had original electrolytics, tubes, and most other parts. I've owned it for maybe 30 years, and that entire time it sat unused. (I have many amplifiers and radios like that, some dating back to the 1910's.)

Strawman argument. Tom, you continue to use anecdotal personal observations passed off as factual information to deflect the issues.

In the real world, none of those radios were designed to last more than several years, and at minimal cost to the manufacturer. We're not talking 1960's era HP test gear, but equipment that was aimed at a cheap consumer market. I can think of numerous examples of known issues in early boat anchor gear that are age related.  For one example, the power transformers used in the Hallicrafters HT-32 are known to develop shorts between the HV and rectifier filament windings.  Prudent restorers replace the tube rectifiers with diodes. Of course, there are quite a few HT-32 parts donors out there from owners who figured they could just plug them in, and run them.

A majority of the early Atwater Kent cathedral sets have very weak transformers. I've seen them fail days after a set was placed in use, after complete restorations. In some cases, the tar used to seal vintage transformers is acidic, shortening their usable service life. The same for the tar filled Bakelite block capacitors used in Philco sets... tar filled, and one that doesn't have major leakage issues is a rare find. Same for wax sealed paper caps. Heat may not harm tubes or other components, but to say heat does not promote aging defies the datasheets provided by many component manufacturers.

Plugging in vintage ham set and using it as is is the same as playing Russian Roulette... sometimes with a six shooter, but most likely with a 45 with the clip removed and a bullet in the chamber.

Pete
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G3RZP
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« Reply #43 on: February 09, 2015, 04:43:26 AM »

It is arguable that there are components to which the heat/MTBF relationship applies and there are those  for which heat has little effect because of various design or manufacturing inadequacies - those will fail anyway, quite possibly if not even used. As an example, although hardly BA stuff, is tin whisker formation temperature related?
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W1BR
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« Reply #44 on: February 09, 2015, 04:53:24 AM »

Metallurgy and compressive strength seem to be the leading causes. A lot of those problems appear to have peaked with  the lead-free environmental initiatives.  But, let's not get too political Smiley

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