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Old 10th January 2017, 07:36 PM   #2041
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Quote:
Originally Posted by ArcticBreaze View Post
I bought an arduino the control my mash-tun
I only have a little experience coding for microcontrollers, but it is certainly a different kind of game, when you have no operating system to do all the background chores for you.

I used to love coding at one time. Eventually I realized it was destroying my body (carpal-tunnel, other RSI, lack of exercise), destroying my free time (what free time? Coding soaks up all your time), destroying my social life, destroying my abilities as a musician (I was coding instead of practicing), and destroying my connection with nature.

It's a lonely life, living with your head stuck inside a tin box full of digital bits, isolated from the world around you.

It's not for me any more. When I'm not working, I'd rather be enjoying my wife's company, playing guitar with my friends, watching the deer come out to eat at dusk, or trying to get another watt out of a 6BK5.

-Gnobuddy
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Old 10th January 2017, 07:42 PM   #2042
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Originally Posted by ArcticBreaze View Post
oh and test equip sounds good I need a good tube tester
I don't know much about tube testers, unfortunately. But I keep finding little bits of gear I wish I had: a small audio signal generator that can put out up to 10V RMS sinewaves, a way to generate sine tone-bursts from the signal generator, a simple speaker test setup (for measuring speaker fundamental resonance frequency and/or other Thiele-Small parameters), et cetera, et cetera.

I'm sure that many people who've been tinkering with tubes/valves for a long time have come up with some clever little tools-of-the-trade of their own invention. Maybe we could share some of those ideas here.

-Gnobuddy
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Old 10th January 2017, 08:39 PM   #2043
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Quote:
watching the deer come out to eat at dusk
We had 6 deer come to eat most every night in our backyard. Between hunting season and being run over by pickup trucks, there are now 3. The big buck's head is probably hanging on someone's wall by now.

Quote:
or trying to get another watt out of a 6BK5.
I picked up 270 cheap tubes last time I was in Florida at ESRC. Unfortunately I haven't put power to any of them yet......soon. I really want to make a vacuum tube ladder filter, that's what some of those tubes were for.

Quote:
I don't know much about tube testers, unfortunately.
At one time I had 3 tube testers. One basic emission tester, and two transconductance testers. I found that none of these could reliably weed out all bad tubes. I had a big bag, maybe 250 used 6U8 tubes and a KT88 HiFi amp design that used them. I ran all of the tubes through the amp, testing for DC voltages, gain and distortion. I ran maybe 30 or 40 tubes through the amp, ran the stats for all the tubes using the 6 sigma tools that I had been taught during my engineering career at Motorola to determine the specs needed to ensure that every tube that I tested would work in the amp.

I then ran all of the tubes through the amp, and tested each one to those specs. There were maybe 20 tubes that didn't make the cut, each rejected for one or more out of spec parameters. None of the tube testers could reliably find those bad tubes, and one of them failed several good tubes. The transconductance testers did a decent job of finding the tubes that failed the DC specs, but couldn't find those with high distortion, and some were really bad.

After that experience, maybe 12 years ago, I sold all the tube testers.

Another forum member who wants to remain anonymous has sent me a vacuum tube curve tracer. I had about a day to play with it last year, but it really needs to find a spot on a workbench and a dedicated oscilloscope. I really want to run a big bag of tubes (I have several) through a curve tracer then stick them all into a working circuit. That will be a learning experience, then maybe we can all figure out how to build a tube tester that really works.

Quote:
tinkering with tubes/valves for a long time have come up with some clever little tools-of-the-trade of their own invention.
Most of the time I work with one or more bench type power supplies, all Ebay or Hamfest sourced old stuff, a scope and a handful of $4 digital multimeters. I also have an old HP 8903A distortion analyzer and a HP204C audio oscillator. You can do a better job at making the same measurements with a PC and some software.

When designing an amp from scratch, I dial everything in with external power supplies to figure out what the circuit really likes, and then design a power supply to give me those voltages. Sometimes it's an iterative process if there's no cheap transformer to get me there.

Quote:
I used to love coding at one time. Eventually I realized it was destroying my body
Sitting in general for long periods of time is bad. Sitting and staring at a glowing plastic window into a virtual world is probably worse.

I worked in an RF IC design team at Motorola. I used to design RF circuits and microprocessor controlled stuff for testing and evaluating our chips. I created "reference designs" to showcase their abilities. Often these reference designs were fully functional multi band two way radios. This stuff came easy to me, but that was 3 years ago. In that short time I find that I have lost a lot of that mental sharpness, so I'm thinking about designing a ham radio or something like that just to see if I still can do it.

Quote:
playing guitar with my friends,
I went through a period of time where I was having serious pain and numbness in my arms, hands and fingers. At one point I couldn't even drive a car, much less play the guitar. After giving up on doctors who just wanted to feed me more pills, a frustrated internet search led to the discovery that all of this was caused by a beta blocker medication that I had been taking for 25 years. Within a couple of weeks of stopping the med, all the pain vanished, and most of the major numbness is gone. Winter was always worse case, but so far so good. My fingertips are still numb enough that I drop things, can't get the key into the door lock, and have trouble with the guitar, but hey it's a major improvement. Soldering used to be impossible, but I have wired up the synth and only soldered my fingers a few times.....about normal for me. I'm even going to try SMD stuff again. Still have to proof read and correct an awful lot of my typing though.

Then I read about how Keith Emerson ended his life due to pain and numbness in his arms and hands, and wonder....did he take the same stupid pills?
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Old 13th January 2017, 08:57 AM   #2044
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Quote:
Originally Posted by Tubelab_com View Post
We had 6 deer come to eat most every night in our backyard.
No deer in our pocket-handkerchief sized yard, but there is a big park and open farmland within a few minutes drive. Last time there, a doe came out of the shadows and ended up grazing in the ditch less than ten feet from our idling car. I guess she was hungry (snow on the ground) and used to cars.

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Originally Posted by Tubelab_com View Post
None of the tube testers could reliably find those bad tubes, and one of them failed several good tubes.
Now, that's a bit bothersome!

Quote:
Originally Posted by Tubelab_com View Post
couldn't find those with high distortion, and some were really bad.
So much for the supposedly universally-applicable three-halves power rule for triodes?

Do you happen to know what causes that sort of high distortion in a tube? Perhaps misshapen or misaligned electrodes? Presumably you have to somehow generate an abnormal electric field inside.

Quote:
Originally Posted by Tubelab_com View Post
You can do a better job at making the same measurements with a PC and some software.
I want to do things like quickly find the right value of small-signal pentode screen grid decoupling cap to get bass response down to 80 Hz.

For this sort of thing, I decided a small analog audio signal generator would be quicker and more convenient than a PC (plus mouse, keyboard, display, external buffer electronics, etc, etc).

I would actually love to pair that sig-gen with an old-fashioned AC analog meter that reads in decibels. They don't make those any more, and I have zero budget right now. Mebbe I can cook up something that goes between the audio signal and a cheap DMM on DC V range, so that if the meter reads "-3 V", it means "-3 dB".

Quote:
Originally Posted by Tubelab_com View Post
When designing an amp from scratch, I dial everything in with external power supplies to figure out what the circuit really likes, and then design a power supply to give me those voltages.
I love the idea, but have no suitable external power supplies. Mebbe I should slap some diodes and caps on a Triad N68X and make a (fixed) bench supply with roughly 160V DC and roughly 320V DC.

Just had an interesting idea. Why not put a power MOSFET in series with the rectifier diode(s), and turn off the MOSFET whenever the filter cap charges up to a preset voltage? A sort of crude 120 Hz switching regulator to let you dial-a-voltage up to the maximum you'd normally get from that particular transformer and rectifier arrangement?

Quote:
Originally Posted by Tubelab_com View Post
all of this was caused by a beta blocker medication that I had been taking for 25 years. Within a couple of weeks of stopping the med, all the pain vanished, and most of the major numbness is gone.
I'm not normally in favour of lawsuits, but in this case, I really wish someone had awarded you a couple of million bucks for the (literal) pain and suffering they'd caused you over the years.

It may be a couple of days, but I'll try to make sure there is actual guitar-related electronics content in my next post. I don't want this thread to end up getting moved to "The Lounge".

-Gnobuddy
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Old 14th January 2017, 06:41 PM   #2045
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I'm not normally in favour of lawsuits.......
I'm not either, and I'm not looking to sue anyone. I just wish I figured out what was going on a lot sooner. There is still something wrong with my cardio pulmonary system since I have been known to turn blue from time to time. Blue spots will develop on the skin surface over any muscle that I work hard......IE my shoulders will develop blue patches, which will eventually grow to cover my entire shoulders when shoveling snow for an hour or so. It's been going on for 30 or more years, so it's not going to be found now.

Quote:
It may be a couple of days, but I'll try to make sure there is actual guitar-related electronics content in my next post. I don't want this thread to end up getting moved to "The Lounge".
Yeah....I have some tube stuff in the works, but right now my workbench looks like a 1990's vintage Hewlett Packard repair shop. Need to fix up some of this stuff for the upcoming hamfest season. Whatever I sell will pay for this years projects, and to keep Tubelab alive or at least one more year.
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Old 17th January 2017, 06:57 AM   #2046
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Moving back to the topic at hand, a chap downunder has spent some time looking at cheap SE OPTs and found that 12V downlight transformers work rather well.

See this thread Background to a new SE amplifier on Aussie Guitar Gear Heads
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Old 18th January 2017, 03:59 PM   #2047
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Originally Posted by thoglette View Post
...12V downlight transformers work rather well.
Very cool!

I used to be an AGGH member, and I'm familiar with Grant Wills' amazing ability to conjure up good-sounding amps from a handful of improbable components.

I wish those halogen transformers were easier to find around here. I've not had much luck so far.

-Gnobuddy
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Old 23rd January 2017, 02:14 AM   #2048
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I got a stupid idea into my head. It wouldn't go away, so I had to build it. Of course it didn't do quite what I planned, but it did have a WHOLE bunch of gain. 10 mV of input gives 100 volts of output. I now have a few dozen more ideas to try, but this design is a dead end.

Now does anybody have an idea as to what it was supposed to be?
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File Type: jpg LadderBottom1_x.jpg (758.7 KB, 77 views)
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Old 23rd January 2017, 03:44 AM   #2049
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No idea, but I'm intrigued by how few passive components there are, to support four (?) valve stages. Some direct-coupled stuff happening, maybe?

-Gnobuddy
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Old 23rd January 2017, 03:07 PM   #2050
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Yes, all 4 tubes are wired together as a really tall cascode stage, or two of them in a balanced setup. It was my first attempt at a vacuum tube Moog ladder VCF for a music synth. It did actually work, but the plate resistance of the wimpy TV tuner triodes doesn't vary enough to cover even one octave, so it has been deemed a dead end.

I will rip it up and rewire it several times before I either make a good filter, a pile of dead parts, or a scrap piece of well used breadboard.......probably all 3. I have one dead tube already. One heater doesn't light up in the twin triode. Either it was dead from the start, or a seriously violated HK voltage spec helped it die.

Since it isn't a sub $100 guitar amp, I dug up a 2 1/2 year old vacuum tube modular synth thread and stuck my experiments there. That's where my future exploits with this board will be posted.
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