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Author Topic: Goodbye tubes.  (Read 6739 times)
KM1H
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« Reply #105 on: August 14, 2019, 03:01:45 PM »

Brian, beside you wasting a lot of forum space who ever said that SS wasnt generally more reliable than tubes??? All I have done is point out exceptions and unproven guesstimates....which may be completely accurate, once enough hours have been reached.

It seems some of the desk bound types cant fathom this and their only defense is insults. Maybe management on here should step in on a few.

I have been familiar with MIL-HDBK-217E (whatever revision was current then) since the mid 60's thru decades later as a civilian tech thru engineer. Working on military projects it was a separate reliability group who was responsible.  Was that your job Brian since you seem to know so much about it?

I never worked on NASA projects and unlike some try not to post on subjects I do not have the familiarity with to make a meaningful reply....yet feel the obsession to blabber away anyway and often with misinformation that they will never admit to.

As far as the MRF-150 is concerned, the actual Motorola part as used in thousands of transceivers certainly had its share of failures without Hammy Hambone being involved as the cause. Many of those failures were unexplained by the manufacturers and the requirement to use only those that were matched within a fairly narrow bias range could be used. Maybe the Japanese didnt buy a copy of MIL-HDBK-217E.

The Japanese versions, 2SC2879, used by other companies, seemed to be more reliable except in CB amps Roll Eyes  Neither is readily available from a quality source (Fleabay is mostly Chinese counterfeits) and then the price soars. OTOH the 572B just keeps chugging along and even from China once they were pretty much forced into producing quality....their government does not like their legitimate companies such as Shuguang being seen in such a bad way and senior managers were often shot across many industries. Saving face is a big thing to the Chinese.

I never worked on NASA projects but I have worked on CIA projects Grin

As an ET in the USN MIL-HDBK-217xx was never mentioned except possibly as a reference in the manual. My job was to fix the gear and not look for things that were outside my rate description. The navy is funny that way Roll Eyes
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KM1H
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« Reply #106 on: August 14, 2019, 03:05:41 PM »

Quote
Shame on you mean fellows for picking on gentleman Carl.

Was that an insult Mike? I havent noticed any other comments from you in ages so wonder if you Trolled here. If so Im very disappointed as I thought you were above that low class stuff.

Carl
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K4EMF
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« Reply #107 on: August 14, 2019, 03:29:53 PM »

So.....now that we've settled that debate.   Anyone know where I can get a brand new 160m - 10m amp capable of a 100% duty cycle carrier for say less than $600?

Tube, solid state or even flux capacitor would be fine by me.
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KD8MJR
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« Reply #108 on: August 14, 2019, 03:34:03 PM »


Apples to apples.

Next, I assumed the very lowest grade of plastic MRF-150 transistor, running at a junction temperature of 100C, continuously (full power).  Continuous, max temperature operation is generally the worst-case for MOSFET transistor reliability and is VERY conservative compared to the occasional, intermittent duty cycles seen in amateur service.  So I stacked the deck against transistors.  A LOT!

For the 572B/T160L I assumed full power, continuous operation, with zero penalty for thermal shock and mechanical vibration - the Achilles heel of tubes, which is seen a LOT in amateur radio applications.  Continuous operation is where tubes are at their very best for in-service reliability.  So I zeroed out tow of their primary failure mechanisms and emphasized a key tube strength.  Every advantage to the tubes.

Doing the (very simple) arithmetic in the Handbook FOR THIS APPLICATION yields the following FIT rates (Failures In Time - per billion hours) - a lower number is better and MTTF is the reciprocal (in hours of the FIT rate):

MRF150 MOSFET transistor (worst case assumptions):  4,262 FITs
572B/T160L tube (under best case assumptions): 75,000 FITS


So, as a starting approximation, giving every advantage to the tube, the transistor is (very generally) at LEAST 18x more reliable than the tube.  Add in realistic thermal and mechanical shock derating for the tube and that difference reaches and exceeds 100x.  And, if you repeat the excercise, you'll discover that similar numbers can be produced for the for the 3-500Z, 3CX800, 1000, etc.

Brian - K6BRN

Yeah this would come as no shock to me.  I would say that even 100x more reliable in the real world is still a bit conservative.
For Ham Radio operations it might be around 50x more reliable because Hams treat their equipment well and by the nature of the Hobby they are not stressed by vibrations or other effects like a lot of power cycling.  It must have been a nightmare in the old days to use tubes on things like Planes and car radios.  I would imagine the failure rate was off the chart.  Of course that was before my time so maybe someone who was in the field back then can give me a history lesson on that.

73s
Rob


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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
AA4PB
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« Reply #109 on: August 14, 2019, 04:18:13 PM »

I worked on tube equipment used in the S2F aircraft back in the 1960's. You would think that carrier landings would be really hard on tubes but the majority of failures occurred when the equipment was first powered up, rather than during a landing. Originally they had a tech go out and power up all the avionics equipment (communications, navigation, and radar) several hours before the pilots manned the aircraft in order to check that everything was working okay. Later on they decided that most of the failures were occurring on power-up so they discontinued the early pre-flight check and just let the pilots check it on their preflight. If it worked for the pilot then it was not powered down again until the flight was finished. The overall failure rate was NOT improved by having the early check because it just added an extra power cycle so it was just as likely to fail the next time the pilot turned it on.

I was amazed to find that the S2F still had an ARC5 receiver. I was very familiar with them from my amateur radio experience during my teenage years (I purchased them new in the original carton for $10 each). It was nice to be able to replace the "bathtub" capacitors with the exact replacement from Navy stock instead of patching in a radial capacitor.  Grin
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Bob  AA4PB
Garrisonville, VA
KD8MJR
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« Reply #110 on: August 14, 2019, 04:49:17 PM »

I worked on tube equipment used in the S2F aircraft back in the 1960's. You would think that carrier landings would be really hard on tubes but the majority of failures occurred when the equipment was first powered up, rather than during a landing. Originally they had a tech go out and power up all the avionics equipment (communications, navigation, and radar) several hours before the pilots manned the aircraft in order to check that everything was working okay. Later on they decided that most of the failures were occurring on power-up so they discontinued the early pre-flight check and just let the pilots check it on their preflight. If it worked for the pilot then it was not powered down again until the flight was finished. The overall failure rate was NOT improved by having the early check because it just added an extra power cycle so it was just as likely to fail the next time the pilot turned it on.

I was amazed to find that the S2F still had an ARC5 receiver. I was very familiar with them from my amateur radio experience during my teenage years (I purchased them new in the original carton for $10 each). It was nice to be able to replace the "bathtub" capacitors with the exact replacement from Navy stock instead of patching in a radial capacitor.  Grin


Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob
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AA4PB
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« Reply #111 on: August 14, 2019, 05:25:09 PM »

Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob
Whenever the aircraft reached a certain number of operational hours (don't remember how many) then it was brought in for scheduled maintenance. We pulled all of the avionics equipment, brought it into the shop, and gave it a complete check to ensure that it met all original specifications. Tubes were only replaced if needed to bring the unit up to original specs. A detailed record was kept for each piece of equipment showing when it was in for repair and what was done to it. When the tech had the work finished, he had to get a QC guy to inspect it, recheck final specifications, and sign off on it before it went back into the aircraft. The failure rate really wasn't too bad but then the equipment was mounted on shock mounts with all mounting hardware safety wired. In addition, safety-of-flight equipment like radios and navigation stuff always had two independent systems in case one failed in flight.
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Bob  AA4PB
Garrisonville, VA
KM1H
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« Reply #112 on: August 14, 2019, 05:32:58 PM »

For Ham Radio operations it might be around 50x more reliable because Hams treat their equipment well and by the nature of the Hobby they are not stressed by vibrations or other effects like a lot of power cycling.  It must have been a nightmare in the old days to use tubes on things like Planes and car radios.  I would imagine the failure rate was off the chart.  Of course that was before my time so maybe someone who was in the field back then can give me a history lesson on that.

I have worked on tube equipment since 1955 when I started with a home brew regenerative RX and a 6AG7-6L6 TX for 80/40M.

Next came a BC-454 and 455 and it still continues thru 2019. I have been repairing/refurbishing radios for others and myself, including auto radios, since the mid 60's after being trained as a USN ET and later as a Service Tech at National Radio, one of the great names of the past.  

While I have plenty of modern gear including lots of SS up into the microwaves where I design and build much myself using state of the art components. While tubes provide most of the high power RF, up to 1500W, the ones for 1296 and 2304 MHz have been replaced by surplus commercial SS modules as the prices have plummeted; 903 MHz will be next. I doubt that anything lower in frequency will go SS since I have spares for all to last me in this life Grin

I also have a few operating benches dedicated to hollow state and used often on AM, SSB and CW.

I have found that auto tubes seem to last as long as any others since the types were common since 6.3V filaments became standard around 1932 for the new auto radio industry. Some real early glass tube types became microphonic in auto radios detector/first audio stage but you have to consider what passed for roads back then and vehicle suspensions were punishing even to humans. With the metal octal tubes debut in 1935 that problem went away except for replacing the old types which last just fine on modern roads.

Carl
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KD8MJR
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« Reply #113 on: August 14, 2019, 06:14:48 PM »

Wow that is interesting.  So how bad was the overall failure rate for various modules.  Did they have to be replaced within a certain amount of hours or did they go by landings or what?  I assume that they would always chuck all the tubes during a service procedure.

73s
Rob
Whenever the aircraft reached a certain number of operational hours (don't remember how many) then it was brought in for scheduled maintenance. We pulled all of the avionics equipment, brought it into the shop, and gave it a complete check to ensure that it met all original specifications. Tubes were only replaced if needed to bring the unit up to original specs. A detailed record was kept for each piece of equipment showing when it was in for repair and what was done to it. When the tech had the work finished, he had to get a QC guy to inspect it, recheck final specifications, and sign off on it before it went back into the aircraft. The failure rate really wasn't too bad but then the equipment was mounted on shock mounts with all mounting hardware safety wired. In addition, safety-of-flight equipment like radios and navigation stuff always had two independent systems in case one failed in flight.


Thanks for the history lesson Smiley  It's always nice to learn something from somebody who was there.
BTW I was watching a show on the Curiosity Stream about rebuilding WWII aircraft.  One thing that caught my attention during the episode on the P51D was that they mentioned that the engine was only designed for about 100 hours of flight time before it was literally dumped.  Although the guy said the odds of a pilot getting through 100 hours without something else  happening to the plane was pretty slim.


73s
Rob
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KD8MJR
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« Reply #114 on: August 14, 2019, 06:23:35 PM »


I have found that auto tubes seem to last as long as any others since the types were common since 6.3V filaments became standard around 1932 for the new auto radio industry. Some real early glass tube types became microphonic in auto radios detector/first audio stage but you have to consider what passed for roads back then and vehicle suspensions were punishing even to humans. With the metal octal tubes debut in 1935 that problem went away except for replacing the old types which last just fine on modern roads.

Carl

And here I was thinking that every time you dropped in a big pothole the radio probably went out  Grin
I guess if everything is constructed well it can take a fair amount of abuse before something cracks or gives way.

As for spare parts for the amps, I know what you mean.  I have a load of spare finals right now.   I just spent $400 on a pair of ARF1500 for my THP2.5Kfx.  The manufacturer says they are still being produced but I was not taking any chances.  I monitored Digikey and Mouser and saw the stock slowly going down from hundreds to just a handful. So I knew it was time to pull the trigger.  Now I have spares for every amp in the shack and shop. Plus a few extras of the cheaper stuff.

73s
Rob
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W9IQ
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« Reply #115 on: August 14, 2019, 06:36:36 PM »

For Ham Radio operations it might be around 50x more reliable...

I will take 50x as a defensible number. Now that the surviving posters are in violent agreement, can we move on?

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KM1H
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« Reply #116 on: August 14, 2019, 07:06:36 PM »

Quote
And here I was thinking that every time you dropped in a big pothole the radio probably went out  Grin
I guess if everything is constructed well it can take a fair amount of abuse before something cracks or gives way.

Often it was the driver or passenger who went out Roll Eyes

Common damage in the 30's was wire wheel rims, tires/tubes, a bent front axle or wishbone in Fords. Independent front suspensions got their own share of damage.

With a lot of bodies framed in wood as late as 1935 those loosened up and added a lot of creaks and groans plus many roofs were tar covered cloth inserts as full body stamping/welding into one piece was playing catch up. Auto radio antennas had no common agreement; some were under a running board, in the cloth roof, attached to a rear spare tire ring, a little rod above the roof and turned by an inside knob, were among the most common. The cowl mounted telescoping antenna that most remember took over in the 1936-37 years and led by Philco

No, I wasnt around then but read a lot of auto industry magazines at libraries or what I picked up in the usual low cost places Grin

Quote
As for spare parts for the amps, I know what you mean.  I have a load of spare finals right now.   I just spent $400 on a pair of ARF1500 for my THP2.5Kfx.  The manufacturer says they are still being produced but I was not taking any chances.  I monitored Digikey and Mouser and saw the stock slowly going down from hundreds to just a handful. So I knew it was time to pull the trigger.  Now I have spares for every amp in the shack and shop. Plus a few extras of the cheaper stuff.

I stocked up when production volume was high and tube prices low. Most of my sealed box NOS came from hamfests, early Fleabay, estate sales and the like.  For awhile I was a mail order/hamfest reseller for CeCo in NYC of the popular Eimac tubes such as 3-400 and 500Z until Richardson screwed it up for everybody with a sole source agreement from Eimac. They also have all the original Cetron 572B tooling and are just sitting on it.

Carl
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KM1H
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« Reply #117 on: August 15, 2019, 07:53:42 AM »

Quote
I still haven't seen any MTTF ratings for tubes that are commonly used in amateur radio linears. Can you quote or reference any?

Since you enjoy sitting at a keyboard why not look for yourself?

Im going to take a nice long walk, get some Vitamin E, and then mow the lawn.
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W9IQ
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« Reply #118 on: August 15, 2019, 08:02:58 AM »

Since you enjoy sitting at a keyboard why not look for yourself?

Im going to take a nice long walk, get some Vitamin E, and then mow the lawn.

I did look rather extensively. Nothing found. I even read Bill Orr's "IVS" pontification but it appears that those ratings never took hold.

You are slacking, old man. I have already moved 80,000 pounds of hay and moved herds between pastures. My grass cutting involves 8 to 12 foot widths per pass. I am off tomorrow and Saturday so I should be able to get a lot more ranch chores done.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K6BRN
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« Reply #119 on: August 15, 2019, 12:02:07 PM »

This is getting too funny.  I'm checking in from a boat on Cayuga Lake.  Not mowing the lawn.  Not bailing hay or mucking out the barn.  I'm done with cattle, horses, ponies, chickens, peacocks, etc.  Did enough of that when I was young, working my aunts farm.  Right now, water is great, weather is great, concert tonight, play last night, great local food....   Life is good.  Will be moving on to QTH#2 on the Sound later this week. 

Concerning Carl's question... way earlier... just look me up on LinkedIn.  All you ever want to know is there or on line.  Degrees, patents, awards, papers.  Live it up and satisfy your curiosity.  No need to post it here.

On the tube vs. transistor reliability debate ... that's pretty much done.  Anything further is just beating a dead cow... um.  ...  horse.

Have a good week, gentlemen.  I'm going to cruise up to Taughannock Park now and see what's happening.  Boat is full of family and friends.

Brian - K6BRN

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