Building the uTracer

What people are working on at the moment
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Paul Barker
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#91

Post by Paul Barker »

You are a star. Thank you.
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#92

Post by jack »

Paul Barker wrote:The EMI suppression is probably out of a microwave. I keep them saves making my own.
Do you really need that - the laptop PSU will definitely already have one that complies with all the regs... Not really necessary.

Having said that, I'm using a filtered IEC 60320 C14 (aka "kettle socket") as my mains input as I'm using a "no brand" generic PSU and can't vouch for its quality...
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Paul Barker
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#93

Post by Paul Barker »

Good point.

the power supply has turned into a farce anyway. I made the holes for a pregrommeted leed and screw on face plate I took from some cheap hifi then discovered it had no earth. So now I have to alter it to take a gland and feed a 3 core leed through. The smps I was going to take apart and solder direct to. But on ispection it is so tightly packed you can't get the heat shields/sinks/rfi shields off without unsoldering, which I don't want to risk. So I shall have to get a clover leaf leed. That shall have to be joined to the incoming 3 core, so I either use connecting strip or may aswell use the microwave EMI supressor anyway.

The idea originally was to make it all internal, externally just a leed. but it is not going to plan.

Good job I am only a hobbyist. If I was an OEM designer I would be sacked!
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#94

Post by jack »

There's a new GUI update issued by Ronald that allows positive grid voltages...

See http://dos4ever.com/uTracer3/uTracer3_pag12.html#FAQ17
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#95

Post by Paul Barker »

Semi finished the case work.

Sadly the Dell laptop supply I bought is a dudd it puts out 11v.

So I am back on my bench supply.

I haven't made up banana plug leeds yet so clip leeds are in play.

Here I am testing a PM5X. It has a 6v filament so I used a trick to get a 0v bias setting. Connected Cathode of uTracer to plus of 6v filament supply so the -3v grid line is actually zero volts and so ever grid line is +3v on what it writen.

This looks like a linear veritable old valve. mu of 18 I am inspired to try it for sound. I shall just have to build mono while I enjoy these old valves as I hardly have more than one of any but I have a fair few DHT's of this era.

New GUI installed. No comment as yet, had a number of glitches but may be my fault. Just need to get used to it. Not tried the screen supply positive grid volts yet.

Image

Image
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#96

Post by Andrew »

Had good fun this weekend playing with Nick's uTracer, I will say it was very comforting to find many of the valves I have bought, but not had chance to try in a real amp, produce pretty sensible looking curves.

We found one 300B that had a problem but these were old valves that had already been consigned to duty as amp testers.

The one sadness was a 5687, it produced sensible curves with one half slightly down compared to the other but when we tried it in an amp it arc'd over something awful. Putting it back into uTracer it was clear there may have been something odd with it; quite an odd wiggly progression in some of the data points, but nothing really obvious that would point to the valve being truly bad.

My take-way from all of this is that I should look at uTracer as a valve curve tracer and not a valve tester, I would guess that the spot pulsed tests that uTracer uses to power the valve didn't have enough energy in them to create the arc but when we used the valve in an amp with a constant power applied it was enough for it to arc over.

Nick thought it might have been the cathode heater insulation; the valve was being used as a cascade. He may chip in if he can remember much more about the curve.

cheers,

Andrew
Last edited by Andrew on Sun Jul 28, 2013 3:26 pm, edited 1 time in total.
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#97

Post by James »

An update on positive grid curves......

I installed the new GUI and ran an 826 and a GM70.

There is no sign of the previously identified "wobbles"

James.
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GM70.jpg
826-Ia.jpg
826-Ig.jpg
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Paul Barker
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#98

Post by Paul Barker »

James wrote:
There is no sign of the previously identified "wobbles"

James.
what wobbles ?

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#99

Post by Paul Barker »

It may be a freak I should also test the GM70 and see what that sais about it. Next time I'm at the lockup.

By the way how do you guys do your pictures? I am hosting mine on photobucket and will have to start paying at the rate I am going.

Please somebody give me a talk though.

ps I found out how to get rid of the look of wobbles, ronald emailed me instructions which I tried and it works.

In a nutshell after the trace you specify an extra Y axis, make it fit the traced curves in every respect except the wobbles, then show Y2 and not the Y1 axis data. I tried the idea and it works. But you have to do it once the data is captured.

It is possible wobbles portray a problem with that valve.
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#100

Post by Cressy Snr »

https://www.dropbox.com/

This is what I use for my pics. Just follow the instructions after the sign up screen. It really is a good service.
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#101

Post by James »

I must admit,

The 826 that showed wobbles has now died with a suspected internal short. It was always a suspect/sacrificial valve hence it being used for testing the tester!

The 826 traced now is certainly wobble free, as is the GM70.

Re images, I use "save for web" in Photoshop elements to get the size down. Sure there is an easier way.

James.
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#102

Post by James »

One thing I have found that certainly does cause "wobbles" is oscillation. That may be what you have there Paul.

I tried my tester without the AVO ring connection technique or ferrites and the result was random wobbles on most tests.

With my external valve base chassis short link cables are a must.

On the 826 if I don't connect both grid and both anode pins it is prone to oscillation during testing.

James.
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Paul Barker
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#103

Post by Paul Barker »

Plenty to think about.

With the pictures it seems I have just used .7 Gig of 2.1 free Gig so no worries. If I get full I can reduce size of old pics which people will are unliklely to refer to. Don't think I need worry.

But what I meant was how come my pics are in the html and some of you guys your unclear pics are in a little box that on hitting the useless pic it downloads a readable version? How do you do that?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Paul Barker
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#104

Post by Paul Barker »

James wrote:One thing I have found that certainly does cause "wobbles" is oscillation. That may be what you have there Paul.

I tried my tester without the AVO ring connection technique or ferrites and the result was random wobbles on most tests.

James.
I have the AVO method and I have two inductors per ring staggered appropriately.

The clip leeds may not help.

My bannana sockets can screw down onto a wire, I might try making specific links to each valve type where this issue occurs and see if that fixes it. Can't use grid stopper in A2 or I would.
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#105

Post by Paul Barker »

SteveTheShadow wrote:https://www.dropbox.com/

This is what I use for my pics. Just follow the instructions after the sign up screen. It really is a good service.
I share a dropbox with a load of Gas fitters, we syndicate stadards data and instructions which would cost us thousands and we'd need a mobile library to cart around, which we can access on a pda in any home where we can get 3g. It is excellent for that..

I couldn't put these pics on that profile they would rib me from now to my grave.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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