A Simple, Valve Curve Plotter

[pwdrive]

Forgot to mention...It might be worth prototyping it first on a baseboard or whatever with some dummy loads or cheap valves to make sure all the specified voltages and currents can be supplied to the valve socket and also to check for any heat dissipation problems.


Prototyping is good.  

Lawrence.

[AlanBeckett]

High Power Pots seem to be readily available, mainly from China.
Dial 'Rheostat' into eBay.
I haven't a clue what they are meant for. 
If you really do want to do it that way it might be wise to have two in Series - a larger one for course and a smaller one for fine adjustment.

Alan

[Mark Hennessy]

High Power Pots seem to be readily available, mainly from China.
Dial 'Rheostat' into eBay.

Wow - I see what you mean...

For example: http://www.ebay.co.uk/itm/100W-20-Ohm-Ce...2c9f0e8c9f

It certainly looks impressive. Cue the usual chants of "how on earth do they do for the price?"! But seriously, I'm lost for words

[SurreyNick]

That's going to be quite a potentiometer - a large wire-wound job, I'd imagine. And it'll run fairly warm..

It is indeed Mark.
I've done my calcs and unless I'm much mistaken it'll dissipate a maximum 18 watts and I should be able to get away with 8 ohm. So I was going to opt for a 100W 8-Ohm L-Pad like this one (http://www.mcmelectronics.com/product/DI...70-/50-070)
Nick

[pwdrive]

Nick, if you are using pots then this link I put in the archives some time ago is a useful reference and read, most of everything that needs knowing is in there including ratings etc, it's from Bourns the pot maker:

http://www.bourns.com/pdfs/OnlinePotenti...ndbook.pdf

Lawrence.

[SurreyNick]

Thanks Lawrence. I will have a good read this evening. And prototyping on a breadboard is a definite yes
Nick

[Mark Hennessy]

With all this talk of high power wire-wound stuff, I can't resist sharing this: http://powersupply.blogs.keysight.com/20...7006766336

[pwdrive]

With all this talk of high power wire-wound stuff, I can't resist sharing this: http://powersupply.blogs.keysight.com/20...7006766336

Yeah..."Set the controls for the heart of the sun Igor"

Lawrence.

[Alan Douglas]

which together switches the plate, screen grid and control grid,

I would definitely apply grid bias first.  In fact it does no harm to leave it on all the time.

[SurreyNick]

OK Alan, thanks for the heads up. I'll link the switch for GB to the one for the Heater
Nick