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uTracer - tube curve tracer [kit]



 
 
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  #1  
Old September 6th 16, 06:58 PM posted to rec.audio.tubes
Big Bad Bob
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Posts: 351
Default uTracer - tube curve tracer [kit]

On 09/01/16 13:57, Peter Wieck so wittily quipped:
> On Thursday, September 1, 2016 at 3:25:19 AM UTC-4, Big Bad Bob wrote:
>
>>
>> I've been kicking around the idea of making one of these that had ZERO
>> patch cables, and could efficiently deliver up to 0.5A for the plate (at
>> certain voltages), and at the same time, enough current for the heater
>> power. Some edge conditions for KT-series power tubes can conduct some
>> serious current (up to 1/2 an amp), and the heaters can suck up 12W or
>> so. If the power tube can't deliver it's max current at the correct
>> plate voltage, it's essentially "going bad".
>>
>> anyway, that's somethi
>>
>> but yeah, this particular curve tester goes up to 200ma which probably
>> covers most tng that an emissions-only tester wouldn't be able
>> to test for.ubes.

>
> That would be labor-intensive as you would have to have the sorts of selector-switches that conventional tube-testers use to cover all the base options.


electronically, yes. but here's the beauty of it: design ONE such
switch, replicate it 12 times [for compactrons, need 12].

the patch bay on the uTracer does exactly that (from the schematics and
other indirect info on the web site). I would want to eliminate the
patch bay.

Additionally, if you control voltages to the pins, you can run the tube
through a series of tests, such as interelectrode shorts [both cold and
warm], open heater, etc.. You could do 'megger' style testing [i.e.
high voltage microamper conductivity testing] to detect partial shorting
at particular voltages, or perhaps detect gas contamination, based on
tube specs.

I envision the project as having 5 or 6 simultaneous source voltages to
put on a pin (plus "no connect). So 3 bits to assign it, per 'circuit'.
repeat that circuit 12 times, one for each pin, then connect 12 wires
to a 'bus' (basically) that wires up all of the sockets. Some
labor-intensiveness making that, of course, but I'd expect that with
switches or even patch plugs.

the 5 or 6 simultaneous voltages would include ground, heater (which
should be adjustable to either a positive or negative DC value, with a
possible high frequency injection to detect cathode signal from the
heater circuit), 'ground through a current measurement' (for cathode
current, etc.), B+ voltage, G1 voltage, G2 voltage, and possibly a 3rd
grid voltage for testing pentagrid converters. (all of those would be
software adjustable via PWM or similar, and would have scalable current
measurements built in).

all of them could be switched using IGBTs, MOSFETs, and or bipolar
transistors. So the idea would be to build a single circuit capable of
assigning 'one of these' voltages, with a digitally regulated "power
bus" supplying them.

anyway I built THIS already [which intentionally provides up to 400V for
tube circuits as well as +/- 0-12V which works well for a heater supply].

http://mrp3.com/sftpowersupply.html

I've used it to experiment with the idea of digitally regulating
voltages for tube amplifiers, mostly so you can vary their
characteristics - like maybe building ONE amplifier that can vary all of
the operating parameters. You might want to similate a tube rectifier,
or a solid state power supply, to get different sound characteristics.
One reason to use a tube rectifier is the voltage drop at max power -
when you play a guitar through an overloaded amp with a tube rectifier,
you get a kind of 'attack/decay' effect up front when you hit the
strings, due to power supply voltage dropping considerably from the 'no
power' to 'max power' transient. a digital power supply could simulate
this with full control over the decay time and amount of droppage.

anyway, I've been kicking ALL of these things around for a while, long
enough that I'd almost be happy just to see SOMEONE do it as I lack even
a REMOTE chance of being able to fund any of this kind of engineering,
but it has a nice geek factor and so I'd like to see it done.

Ads
  #2  
Old September 6th 16, 07:33 PM posted to rec.audio.tubes
Big Bad Bob
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Posts: 351
Default uTracer - tube curve tracer [kit]

On 09/06/16 10:58, Big Bad Bob so wittily quipped:
> I envision the project as having 5 or 6 simultaneous source voltages to
> put on a pin (plus "no connect). So 3 bits to assign it, per 'circuit'.
> repeat that circuit 12 times, one for each pin, then connect 12 wires
> to a 'bus' (basically) that wires up all of the sockets.


was thinking for a moment, and the EASIEST way to implement this would
be to use a microprocessor on each board, one that either uses a simple
external clock or has an internal clock available. ok you'd have to
flash each one but so what. A $2 microprocessor would substitute for
many $ worth of components, and you could PROGRAM it to do 'whatever'.
Well, _I_ could. downside, having to FCC the board because of the CPU
clock, but getting that to pass is pretty easy [it just costs you $ to
certify it]. Tube testing equipment _MIGHT_ qualify as 'A' type gear
though... [so just use decent engineering practices, yeah].

anyway, if you use a CPU then you could put everything on an I2C bus,
and just give each board a different I2C address. That's 2 wires plus
power and ground [not including the 6 voltages] going to each board, and
since they'd all have "those wires" connected to the same things, it
would be 'busses' again and wiring would not be so difficult.

yeah. I like that. use a micro-P to control the 6 voltages. minimal
external components, using opto-isolators for the high voltage stuff,
drive directly from the output pins. nice! An ATMega 328 would do it,
and it's got a 32-pin QFP that's pretty easy to solder.

now I just need to get $ to fund it... [am I begging too hard?]

  #3  
Old September 7th 16, 02:20 PM posted to rec.audio.tubes
Peter Wieck
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Posts: 2,418
Default uTracer - tube curve tracer [kit]

On Tuesday, September 6, 2016 at 2:32:01 PM UTC-4, Big Bad Bob wrote:
> On 09/06/16 10:58, Big Bad Bob so wittily quipped:
> > I envision the project as having 5 or 6 simultaneous source voltages to
> > put on a pin (plus "no connect). So 3 bits to assign it, per 'circuit'..
> > repeat that circuit 12 times, one for each pin, then connect 12 wires
> > to a 'bus' (basically) that wires up all of the sockets.

>
> was thinking for a moment, and the EASIEST way to implement this would
> be to use a microprocessor on each board, one that either uses a simple
> external clock or has an internal clock available. ok you'd have to
> flash each one but so what. A $2 microprocessor would substitute for
> many $ worth of components, and you could PROGRAM it to do 'whatever'.
> Well, _I_ could. downside, having to FCC the board because of the CPU
> clock, but getting that to pass is pretty easy [it just costs you $ to
> certify it]. Tube testing equipment _MIGHT_ qualify as 'A' type gear
> though... [so just use decent engineering practices, yeah].
>
> anyway, if you use a CPU then you could put everything on an I2C bus,
> and just give each board a different I2C address. That's 2 wires plus
> power and ground [not including the 6 voltages] going to each board, and
> since they'd all have "those wires" connected to the same things, it
> would be 'busses' again and wiring would not be so difficult.
>
> yeah. I like that. use a micro-P to control the 6 voltages. minimal
> external components, using opto-isolators for the high voltage stuff,
> drive directly from the output pins. nice! An ATMega 328 would do it,
> and it's got a 32-pin QFP that's pretty easy to solder.
>
> now I just need to get $ to fund it... [am I begging too hard?]


Not hardly begging too hard... But you are looking at a very small market of well-heeled tube fanatics who have the means to indulge themselves in esoteric equipment, and who are not satisfied with legacy equipment, however high-end. A small subset of a small subset at the least.

I do suggest you go to any of several Crowdfund sites and see what you might be able to arrange. You would have to have a plan, a budget and a schedule, but I expect that if this happens, it would happen there.

Writing for myself and my own needs, I have one basic emissions tester that is enough for 95% of my needs, and one very high-end legacy tester (Hickok 539B) that more than handles the other 5%. That 5% was less than 2%, but I am gradually shifting more and more to tube audio lately, so a tester that actually can test tube quality, including 6550s at proper voltages, is useful - and it does allow me to actually match properly.

But, I cannot imagine needing a curve-tracer now or in my future.

Best of luck with it!

Peter Wieck
Melrose Park, PA
  #4  
Old September 10th 16, 07:24 PM posted to rec.audio.tubes
Big Bad Bob
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Posts: 351
Default uTracer - tube curve tracer [kit]

On 09/07/16 06:20, Peter Wieck so wittily quipped:
>> now I just need to get $ to fund it... [am I begging too hard?]

>
> I do suggest you go to any of several Crowdfund sites and see what you might be able to arrange. You would have to have a plan, a budget and a schedule, but I expect that if this happens, it would happen there.


the biggest problems with crowdfunding sites is that if you don't have a
marketing plan in place for the crowdfund itself, you end up not getting
anywhere. I don't do "face-bitch", I don't to "****ter", and don't have
money to spend advertising [or have a venue for it]. But yeah, it's not
a bad idea, because I've looked into it for OTHER projects as well.





 




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