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Old 25th Jun 2017, 4:37 pm   #1
Doris The Diode
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Default Taylor 45C how good is it?

I have been looking at the Taylor 45C valve setting/information/data hand book and I was wondering if you good people out there have experience in using the valve tester.

The reason I'm asking is because I intend to build a valve tester and want to base it on something and the apeal with the Taylor 45C for me is the simple 5 position voltage changing switch which changes the screen at the same time with just a few combinations of voltages.
It also uses low voltages which again is apealing as I have just the transformer for the job.

One of my questions is, I've noticed that most Gm readings are small and that for example a KT66 is not driven as hard as an AVO valve tester does or the Sussex home brew tester and does this in any way pose a problem or makes one tester better than the other, or a reading more acurate than the other?

I know of the Sussex home brew tester but the box I have is not large enough to accommodate all the switches so by using bana plugs and only the 4 most widely used valve bases and hopefully the Taylor voltages I'll be able to come up with something that works well.

Any advise welcome.

DD
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Old 25th Jun 2017, 5:51 pm   #2
David Simpson
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Default Re: Taylor 45C how good is it?

Hello Doris,
I'd advise you to check out this Forum's "Search" facility. Particularly GREENSTAR's thread of 31/5/2017 :- "Windsor 45B & KT66's". Plus there is heaps of info by several contributors on homebrew valve testers over the years. AVO, MULLARD, TAYLOR/WINDSOR, HICKOK VCM's & Valve Testers- - all operate under P-P AC 50Hz Mains derived voltages. Best to consider building a DC Tester. Much safer & more accurate.

Regards, David
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Old 26th Jun 2017, 4:07 pm   #3
Doris The Diode
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Default Re: Taylor 45C how good is it?

David,

Thank you for the reply, I have searched too but I'll do some more searching.

The project which I want to do will be a DC valve tester, I'm going to have a go at making it simple but worth the while to build.
It won't be as glamorous as the Sussex but will be good enough and will have all the functions all be it in a cruder way as it'll have jump leads instead of turn dials and I want to incorporate a separate transformer for voltages for heaters for the U range as a lot of the radios I repair are of this type or 6.3V heaters.

The voltage parameters and read out of Gm will be more than likely taken from the Taylor 45C data sheet.

DD
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Old 27th Jun 2017, 10:37 am   #4
David Simpson
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Default Re: Taylor 45C how good is it?

Hello again Doris,
Might be worth your while advertising on the Forum for an old knackered valve tester which hopefully has a half decent valve holder panel. For my DC tester, I used the panel out of a junked AVO VCM Mk1. And I've also used a panel out of an old AVO Two-Panel tester for another DC project. Great advantage of having the thumbwheel selection switch, but any old valve tester would do. Means you don't have to faff about sourcing valve holders.
There is a disadvantage in using the Taylor charts, in that they work valves at the lower end of the Ia/Vg characteristic. Better to acquire a copy of the AVO valve data manual &/or an Iliffe valve data book.

Regards, David
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Old 27th Jun 2017, 12:43 pm   #5
Herald1360
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Default Re: Taylor 45C how good is it?

Might be worth considering this approach:


http://www.dos4ever.com/uTracer3/uTracer3_pag0.html
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Old 27th Jun 2017, 2:55 pm   #6
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Default Re: Taylor 45C how good is it?

Well, I'm happy with my Taylor 45C cost me £30.00 but I see they're going for silly prIces now. Mine could do with one new 18 way switch as the click mechanism has worn and it's very stiff. The AVO testers are now out of my reach but the uTracer looks affordable and interesting. Anyone here actually using one I wonder?
Don m5aky
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Old 27th Jun 2017, 5:07 pm   #7
Freya
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Default Re: Taylor 45C how good is it?

Hi Don,
without going off topic too much, the stiff switch on your 45c could be a missing ball bearing if its that type of switch fitted. They changed them 5 times over the years. On the other hand if its the sprung ident arm then re greasing helps no end.
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Old 27th Jun 2017, 7:58 pm   #8
Doris The Diode
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Default Re: Taylor 45C how good is it?

Thank you all for the support and the uTracer is interesting too.

I just wanted to clarify my understanding for Gm:
By varying the grid volts you vary the anode current under a constant voltage, divide one by the other and you get the classic read out e.g. 2.5mA/V result.

My question is, if I want to avoid building and injecting an AC signal into the grid e.g. 100mV and measuring the AC volts across a resistor in the anode circuit, could I not just turn the variable resistor which controls the grid volts by 1 volt and read of the difference in anode current, is this not the same thing?
Or set a grid point e.g. -2V and go up by 0.5V and bellow by 0.5V which would simulate a 1V swing.
If this method is the same then I would not only save space on the front panel by having one meter less but also save the cost of one, all be it around £10.

I am trying to build a tester which is simple, for me anyway.

DD
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Old 27th Jun 2017, 9:00 pm   #9
David Simpson
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Default Re: Taylor 45C how good is it?

Doris, For DC static testing, which is what I suspect you wish to carry out initially, the tests for Gm(mA/V) in theory - are what you say. A small change in the DC potential on the Grid which gives a resultant change in the DC current through the valve. However, if you look up, via "Search" all the bumph which a few of us have banged on about on the Forum for years - from the post war years onwards all the major valve tester manufacturers have cheaply designed their testers to work on mains derived AC. BUT - the tester controls, test procedures, and expected results are all referred to the "RMS" (DC Equivalent) of the AC voltages used. As it happens, these confusing procedures do more or less replicate pure DC(Factory tests) done by valve manufacturers, but can vary sometimes by up to 10 or 15%. Obtaining the Gm can let you determine the DC Amplification Factor Mu.
Dynamic testing(using a signal voltage source on the grid & obtaining the corresponding larger signal voltage on the loaded Anode) results in obtaining the gain "G". But now you're into the realms of "Barkhousens Law" and further valve mathematics.
Best to initially just build a basic Chassis with a Int. Octal valve holder, chose a simple triode which requires lowish Va(for safety), and a reliable DC HT source, maybe just a wee handful of AA or AAA batteries for Heater(6.3V approx.) and Grid Bias. Then play around(safely) with a multimeter to see how the valve behaves.
Any doubts - try & get in touch with another Forum experienced member near you - to mentor you.

Regards, David
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