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Old 15th Feb 2010, 12:20 am   #152
Top Cap
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Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
Default Re: The "Sussex" Homebrew Valve Tester.

Although still awaiting the arrival of the PCB, I decided to try and work out how it will interface with the circuit diagram. I decided to give each terminal node an identifier which may (or may not) help me put together my version of the Sussex VT. The info I have put together may be of some use to anyone else building the same and I have put it here:-

PCB with idents:-
http://homepage.ntlworld.com/lez/Sus...%20circuit.JPG

Overall circuit:-
http://homepage.ntlworld.com/lez/Sus...nstruction.JPG

Please note
1) I have not added the bridge rectifier modification yet.

2) The Heater select switch has vacant positions 2 and 3, this is for adding
1.4 and 2V DC supplies later, for directly heated battery valves.

3) I am hoping to be able to switch just one side of the heaters to allow me more switch option positions later.

4) I have yet to decide on D1 and D2 inputs for the Pin selector switches.

Presumably some form of pre-set current limiting would be required here.

There are two R23's on the original board layout and I have re-labelled it as R27. I also suspect that the LED's (except for LED1 on the PCB) are shown the wrong way round?

As the title of one of the drawings suggests, it is work under construction and hopefully you may find some errors that I have missed.

I am going to wait until the tester is built before fitting any ferrite beads etc., I was going to fit chokes until I realised ... the heater current .. doh!
It might be a good idea though to put one in at the Top Cap Grid connection.

The only other change I have made is to fit backstop diodes across the three relay coils, not shown yet across RL1.
Les
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