Building the uTracer

What people are working on at the moment
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Paul Barker
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#61

Post by Paul Barker »

Some sadness comes from finding out the true condition of your valves.

I have 2 px25's (one balloon) with perfect filaments but no emission.

1 Balloon px25 with nearly normal emission but the filament looks ultra scary, one fishing rod sprung yet filament still drawing correct current. Curves look a little wobbly though.

Then out of the battery valves tested so far the top row are completely dud even though the filament takes current.

the bottom row all test good but not a pair between them. But the beauty is I now am beginning to find out what I have, some old valves no longer marked can be discovered by their trace, if not what they are, certainly what they can do!

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Why did it take me so long to buy a uTracer?
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James
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#62

Post by James »

Paul Barker wrote:
pre65 wrote:Can the device handle positive grid bias (A2) ?
No.
You could use the screen supply as a positive grid supply, GUI is not really optimised for this though.

James.
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Paul Barker
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#63

Post by Paul Barker »

Thanks James, so you could specify the screen supply steps. The only issue is what GUI would make of it?

I suppose the data would be in there you would have to pluck it out and graph it by hand.

Probably need Ronald's help with that.

I was wandering and I know you gave a rational for this not working, are you sure we can't intercept anode connection with +200v for instance and just read the bottom line +200v at each stage. His circuit sends a burst of B+ from a capacitor but if that burst passes through +200v which is floating as if it were a battery no other part of the utracer sees the potential only the valve's anode sees the potential.

You would have to uTrace the first 200v first then add 200v to that and get all the data for a 500v plot. Then use other charting programs or just buy some graph paper.

Or am I wrong?
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#64

Post by James »

Hi Paul,

My concern is for T17, the switch that connects the capacitor to the valve anode. The MJE350 has a 300V Vce. I believe is this limitation that prevented a higher voltage rating for the uTracer in the first place.
Whilst in normal operation, there is of course voltage dropped across the valve, so even at 300V on the anode, the transistor will not need to switch this.

The issue is that Ronald designed the uTracer to be in effect short circuit (a-K) proof, in which has the transistor will see the full 300V.

I think the problem with a series connected voltage is that this switch will see it in series with the capacitor, and have to switch that full voltage.

I think (may be wrong) it will work until T17 hits 300V or so then the smoke will escape.

To get any benefit I think the additional added voltage will have to be significant, meaning this probably wont take long.............


Best Regards,

James.
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Paul Barker
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#65

Post by Paul Barker »

Off the top of my head as I am in car park no access to circuit if floating supply negative sits in place of valve amode positive attaches to anode mje350 sees 300v not 500v. Valve sees 500v not 300v. Nomenclature of bottom line just needs changing.
Make sure valve isn't a dead short before tracing with higher voltages.
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Paul Barker
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#66

Post by Paul Barker »

Ronald has corrected me, and as it is such an important matter I have decided to cut and paste what he has written before asking his permission because I feel he would have no issue with me doing so.

"Hi Paul,

I have read the discussion about adding an additional voltage source in series with the anode conection.
I am afraid it won't work. In network theory, you can just "shiftâ€￾ the additional supply across the switch
so that it is "on-top-offâ€￾ the charged capacitor.

best

Ronald"
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Paul Barker
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#67

Post by Paul Barker »

Image
Image
Image
Image
Image
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#68

Post by James »

Hi Paul,

Be sure to wire the socket pins in a "ring main" as suggested in Ronald's instructions.

I tried it without, just for interest. The result is horrible oscillation, just as predicted!

James.
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Paul Barker
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#69

Post by Paul Barker »

Thank you James.

As you see it is as far as it is going today.

Fore warned is for armed.

Maybe for the next uTracer I may need a larger case to get the 211, GM70, 212 and the 833a bases mounted. :D :wink:
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IslandPink
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#70

Post by IslandPink »

Nice work Paul . You've got some fancy drill-bits there !
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Dave the bass
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#71

Post by Dave the bass »

Manicure.

Pronto.

Before anymore pics please :-)
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DTB

PS. Nice work on the Tester, I've been following this thread.
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Paul Barker
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#72

Post by Paul Barker »

Dave the bass wrote:Manicure.

Pronto.

Before anymore pics please :-)
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DTB

PS. Nice work on the Tester, I've been following this thread.
I haven't had time to go through the list of nailbars you sent me Dave, but it is a high priority spend on my beautification a close second to the but sack and crack wax..
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Paul Barker
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#73

Post by Paul Barker »

IslandPink wrote:Nice work Paul . You've got some fancy drill-bits there !


thanks, the step and cone bits are great for plastics.

With the cone it is easy to go too far.
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IslandPink
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#74

Post by IslandPink »

It is The Claw , Kev ( sorry - Dave )
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Andrew
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#75

Post by Andrew »

Has anyone said it?













Shoddy
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