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 > Remembrances of vacuum tube days

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ktmrfs

Portland, Oregon

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Posted: 12/12/20 07:05pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

JKJavelin wrote:

I sure don't miss the electrical shock you can get from those tubes if you didn't ground them (yes, with the TV unplugged). I got it several times.
JK


Actually shocks were not just a "tube" problem it was very common in a lot of solid state equipment, that was caused by manufacturers being cheap skates and not using a transformer in the power supply and tying one side to the 120V line DIRECTLY to the chassis.. [emoticon]

It is called a "HOT" chassis and if not careful when servicing would end up biting you or worse yet becoming a pretty good arc welder when attaching serving equipment like oscilloscope ground to the chassis..

With most older equipment having non polarized line cords you can imagine the havoc that can cause when the HOT side of the line ended up on the chassis.

Spent a lot of my younger yrs servicing 1970s-1990s consumer stuff with one hand stuck in my pocket for safety.

And for the record, CRT TVs, the 2nd anode connection to the tube is to be respected.. CRTs can hold a second anode 20KV+ charge for YRS with out power, was taught to take a long flat blade screw driver and a clip lead from it to chassis ground before ever touching that connection..


yup, the bakelite or phenolic knobs on the front are all that protected you from a potential shock on those old sets. First thing I did and do if I come across one of those old units that I want to keep is to switch to a polarized plug, with the neutral side tied to the chassis, especially those with no transformer.


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ktmrfs

Portland, Oregon

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Posted: 12/12/20 07:14pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

mr. ed wrote:

delwhjr wrote:

Started at a very young age by helping my grandfather and then my father repair electronics (TVs, radios and early HiFi rigs. I liked to build Dynaco stereos and loved my McIntosh stereo equipment. I still think the old tube type equipment has a better sound. I worked for many different electronics shops and went into teaching electronics after closing my own shop. I was always sought out by the local hobbyists to fix their Heathkits when they messed up. Eventually I got into computers and networking. When the students quit taking electronics classes(math was too hard [emoticon]), I changed to computers and networking classes. Retired from teaching at the Community college after teaching high school for many years.


Yes, I've heard the same thing about tube amplifiers having a "cleaner" sound. I doubt most people, except true audiophiles, could notice the difference compared to solid state. You mentioned Heathkits. I've built several in my youth along with many Knight kits. Included were ham radio receiver and xmitter, stereo amps and tuners, plus various test equipment (VTVM, oscilloscope, capacitor checker, tube checker, etc.)


Common misconception that tube amps are "cleaner", in reality they are not. What you do get is a slightly DIFFERENT sound sonically, some would say a "warmer" or "fuller" sound that what transistors give. Hard to describe..

Some folks say transistor outputs as being "sterile" compared to tube outputs.

Back to the "cleaner sound" for a second, tubes by nature inject considerable amount of noise into the audio signal. This happens as the filament heater gives off electrons, some of those electrons affect/interact the plates and grids electrons in the process.

Additionally, most tube amps the filament heaters are powered with a AC voltage which if you listen with a good set of headphones you will be able to hear a slight AC 60hz hum in the background with no signal. With good headphones you can also literally hear the electrons hitting the grids and plates in a form of white noise in the background with no signal. Add that background noise to your music and it gives the 1950's "HiFi" sound that you and your parents grew up with.

There are simulators you can add to your system that can add in a simulation of a tube amp if you like.. They also make tube preamps if you like..


tube amps tend to go into limit on max signal more gradually than solid state amps, and the harmonics generated are IIRC even order vs. odd order for solid state. Even order harmonics are less intrusive to the ear. And lots of the early transistor amps would not only hard limit, but oscillate and do really wierd things when overdriven, all of which gave rather anoying sound,

I had an early Scott transistor amp, when driven to near output limit it would start oscillating in the audio range and coming out of limits had real bad transient recovery problems.

Listening to music it was vey easy to hear when it was being overdriven.

Todays transistor stuff is much much better.

Gdetrailer

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Posted: 12/12/20 08:54pm Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:



tube amps tend to go into limit on max signal more gradually than solid state amps, and the harmonics generated are IIRC even order vs. odd order for solid state. Even order harmonics are less intrusive to the ear. And lots of the early transistor amps would not only hard limit, but oscillate and do really wierd things when overdriven, all of which gave rather anoying sound,

I had an early Scott transistor amp, when driven to near output limit it would start oscillating in the audio range and coming out of limits had real bad transient recovery problems.

Listening to music it was vey easy to hear when it was being overdriven.

Todays transistor stuff is much much better.


Yeah, Tube amps do a "soft limit" when over driven, does sound different from transistors harder limits.

Early transistor stuff was pretty primitive and the Germanium based transistors had quite a few oddities with oscillation issues. I had a Olson stereo receiver that used Germanium transistors in the power output that would get unstable and go into oscillation if there was a Piezo electric based tweeter in the speaker system.. Peizo electric tweeters can act like and look like a capacitor to the output driver of a amp.. If there is any instability it will show up quickly with those tweeters.

More modern transistor amps are amazing and to me, sound very well.. While I did enjoy my old tube stereo equipment, what I have now is far superior in sound quality, no output transformers that limit the frequency response or ad non linear artifacts from the transformer saturation.. Far more power and a lot less heat..

I would have kept the old tube equipment but when you have tube stuff that has 40+ yrs on it, you start facing the reality that it WILL be needing to be fully recapped.. Those old can electrolytic caps dry out and then you have to sub in newer modern ones that unless you gut the old cans new caps stick out like sore thumbs. Not to mention the tubes for some of the old equipment can be expensive or hard to find now days..

time2roll

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Posted: 12/12/20 09:18pm Link  |  Quote  |  Print  |  Notify Moderator

Got my start interested in electricity with my grandfather who as a ham radio operator that talked to people all over the US and world to exchange post cards of successful transmission. He transmitted at 2000 watts through a rotating directional antenna. All tube based back in the 1960s and prior. I ended up at some point with call letters WD6EUP but never really made a go of it as the world was changing in the 70s and 80s.

While the rest of my classmates were reading comic books I checked out a book on electric motors. I built a working model from home supplies in the 4th grade. My older brother told my secret to my parents and soon my elementary school was hosting a class to do the same and I was leading the discussion for the 5th and 6th graders to learn about magnetism and magnetic fields. Sorry no tubes involved. Even made the LA Times and OC register for this accomplishment. (my 10 minutes of fame came and went early)

Soon the world was changing from tubes to transistors. Again my grandfather was teaching me about PNP vs NPN transistors and how everything was changing. He stopped with the big shortwave and reverted to just buying radio components to communicate with friends.


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w4phj

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Posted: 12/13/20 08:23am Link  |  Quote  |  Print  |  Notify Moderator

Tubes are still alive and well. My ham radio linear amplifier uses 4ea 811A tubes.


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wa8yxm

Davison Michigan (East of Flint)

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Posted: 12/13/20 03:30pm Link  |  Quote  |  Print  |  Notify Moderator

Speaking of 2nd Anode (And high power broadcast (And ham) transmitters) one Station engineer I Know has what he calls a "Jesus Stick"

Now as it happens I know (From observation not personal expierence) Where that name comes from

IT's a well insulated handel on a rod that's connected to ground

You poke around the high voltage parts and if one is still hot.. Well

OH JESUS is a common exclamation! when you find a fully charged capacitor.

True story
Two Radio engineers one legally blind (has only side vision can not see straight ahead) The other one opens a cabinet.. Thinking it was the Audio Cabinet (nothing dangerous in there) Turns out it was the High Voltage cabinet.

Two brass bars one firmly connected to ground and you can guess what the other connected to. Block of porcelain between them hooked to the door. The top bar is free to fall onto the bottom bar when the door is opened.

Knocked out power to half of the Building (A Office tower)

Or as the stick is named OH JESUS
(Uh. Wrong door there Charlie?)

Though they do make thousand watt and multi-thousand watt Solid State Transmitters Tubes still rule in the multi-thousand stations.

There is a podcast (Ham nation) and a few years ago they have an episode I think it was title 1.2 Gigawatt or some such (the power of the Car that DeLorean tine travel series Back to the Future)

They show a multi thousand watt transmitter

Several episodes include "Tales from the transmitter site" (The aforementioned Radio engineer of Jesus Stick attribution) and he shows off one of the Transmitter tubes and of course his stick.


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MrWizard

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Posted: 12/13/20 04:59pm Link  |  Quote  |  Print  |  Notify Moderator

Jigawatt


I can explain it to you.
But I Can Not understand it for you !

....

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FlatBroke

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Posted: 12/14/20 07:57am Link  |  Quote  |  Print  |  Notify Moderator

Had a 50 Oldsmobile that the OZ4 tube in the radio would burn out frequently so I left the bottom panel off and carried a spare.



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cleo43

Montreal

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Posted: 12/14/20 11:12am Link  |  Quote  |  Print  |  Notify Moderator

Sherwood, Fisher, Dynaco ...
all these are fading in our aging brain.
Now I remember, when young, one of favorite pass time during the weekend is to browse & buy books and LP's , in downtown (Montreal) stores like A&A, Sam The Record Man.

mr. ed

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Posted: 12/15/20 09:00am Link  |  Quote  |  Print  |  Notify Moderator

I also remember living in Levittown, NY, back in the late 40's. Didn't have a TV then, but a neighbor bought one of the first in the neighborhood. It was B&W, of course and had a fairly small screen (compared to today). We would come over to watch Farmer Grey and Felix the Cat cartoons, along with Howdy Doody. The classical music accompanying the Farmer Grey cartoons sparked my lifelong love of that music.

As a young experimenter, I also made a "foxhole" radio receiver, using a
double edged razor blade, safety pin, piece of pencil "lead" and headphones. It was crude but worked, only if in the vicinity of a radio station.

Kids today don't know what they're missing when they get involved in activities that are too passive and non mind stimulating


Mr. Ed (fulltiming since 1987)
Life is fragile. Handle with prayer.

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