DIY valve tester.

[Arkless Electronics]

Well done Richard!

[Arkless Electronics]

Ouch

DC stings doesn't it Fortunately I haven't had a DC shock for some decades, RF burn yes and that's different again.

You a radio ham then Alan?

[Firebottle]

I am Jez, used to do fast scan amateur television (UHF and microwave) as well as radio but that has died a death.

[awkwardbydesign]

Ouch

DC stings doesn't it Fortunately I haven't had a DC shock for some decades, RF burn yes and that's different again.

At least I didn't burn 2 holes in my finger this, as I did with an undischarged 450v cap years ago!

Well done Richard!

Ah, now then, is that well done for making the thing, or well done for electrocuting myself? Is this one of those smiley moments? After the debacle of the smiley question, I am using as few as possible. http://theartofsound.net/forum/showt...lies-necessary
PS, don't take this seriously.

[awkwardbydesign]

Got another question. As the voltage is too high, I have taken the HT from the last diode, but removed the last cap, which gives me 245v. Can I insert (4 x 1N5404?) diodes to ground to lift the voltage by 5 volts? Taking anode current at 245v gives a false reading, as far as I can see.

[Firebottle]

If you look at the valve curves the drop from 250V to 245V is going to make only a very small difference.

However removing the last cap in the voltage ladder will mean you have some AC on the supply voltage.
To reduce the voltage a little try a small value resistor in the connection from the HI LO voltage switch, that feeds C4, 6 and 8.

[awkwardbydesign]

Ah, thanks. I'll try that. On a different note, I had this round on Sunday. http://www.bartola.co.uk/valves/2013...-rui-lourenco/ It made everything I've ever had here look silly. I was considering trying to make one, but then I woke up! It's a bit above my brain power, I fear.

[awkwardbydesign]

A 150 ohm resistor (measured at 154 ohms) in the feed to the caps worked for ECC83s. But of course the current limiting meant that EL34s only receive 240 volts! I guess a bigger transformer is called for, but that isn't going to happen. So for the moment I have a switch to bypass the resistor for the bigger valves, but I think I will order a 25w wirewound pot (preferably 200 ohms) and use that instead. I already have a little 300v digital panel meter on order, so I will be able to set the anode voltage precisely.
If I actually knew what I was doing, maybe I could attempt that DHT pre!

[Firebottle]

I thought this was a good project and have finally got around to knocking one up.

Because I have a multi tapped high voltage power supply and existing multimeters I have made it so these are external to the valve tester chassis;




The impetus for getting this built was having failing ECC83's, out of 4 in the draw only one is a good one

[Bigman80]

Haha, I wish I had the knowledge to just "knock up" bits of kit

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