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Old 29th Dec 2013, 3:14 pm   #1021
mikeydee
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Default Re: The "Sussex" Homebrew Valve Tester.

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Blimey! What fantastic news. I only just saw this two months late but really glad you posted it. I will try the same on mine.
Rats! I already added the grid stopper but had forgotten it. Such is the way of dipping in and out of projects.
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Old 5th Jan 2014, 9:55 pm   #1022
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi All,
Its been a long time since I last posted so please forgive the absence.
I've returned to the build but I've noticed from the latest circuit diagram that there is a low voltage heater board. Am I correct in thinking that this is addition from Mike's original build.

Thanks in advance.

Rob
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Old 6th Jan 2014, 7:38 am   #1023
mole42uk
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Default Re: The "Sussex" Homebrew Valve Tester.

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Originally Posted by Guitarist28 View Post
I've noticed from the latest circuit diagram that there is a low voltage heater board. Am I correct in thinking that this is addition from Mike's original build.
Correct.

I built mine without it. I haven't used anything except 6.3 volt heaters yet anyway!

Best,
Richard
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Old 6th Jan 2014, 6:12 pm   #1024
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Default Re: The "Sussex" Homebrew Valve Tester.

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Originally Posted by Guitarist28 View Post
I've noticed from the latest circuit diagram that there is a low voltage heater board. Am I correct in thinking that this is addition from Mike's original build.
Hi Rob, the circuit shows how I built my Sussex and was not supposed to be a concise manual for other builds. For those with very few battery valves for testing it probably would be easier to simply apply the required voltage from external batteries applied to the EXT heater sockets. If I needed to test a large range of valves then the idea of having an external Heater supply capable of providing all required voltages would be a good idea.
Les
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Old 6th Jan 2014, 8:47 pm   #1025
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks Richard

Hi Les,
I trust you are keeping well.
Its a good addition as I have a number of portable sets with 7 pin valves so I planning to add this in to my build.

Many thanks

Rob
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Old 6th Jan 2014, 9:02 pm   #1026
Ed_Dinning
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gents, the Sussex transformer was designed with a limited range of heater voltages to keep costs down. The ext sockets were intended to be used for all battery valves and anything higher than 12.6v.
Original units had 4,5,6.3 &12.6V. For the past year I have also added a 2.5v winding after requests for this from people with US power triodes.

Ed
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Old 7th Jan 2014, 1:36 pm   #1027
KeithsTV
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Default Re: The "Sussex" Homebrew Valve Tester.

I have now started on the manual and as mentioned earlier it won't be a quick task but I hope to include not only the circuit and construction details but other useful information on testing valves.

I would also like to include pictures of completed Sussex Valve testers so if anyone would like to take pictures of their completed testers for inclusion, PM me and I'll send details of where to send them.

I would also like to include a couple of pictures of AVO and Taylor valve testers so if any owners can take pictures of their testers please PM me for the contact details.

All contributions used, photographic and other, will be acknowledged.

Keith
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Old 11th Jan 2014, 9:14 am   #1028
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Default Re: The "Sussex" Homebrew Valve Tester.

Here's a little valve test card I edited from the one supplied with my Mullard tester.....

Richard
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Old 11th Jan 2014, 10:02 am   #1029
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Default Re: The "Sussex" Homebrew Valve Tester.

Here's an update to the "Sussex Switch Setting Table" featuring the valves I'm using and interested in.

It's an zipped Excel file, please feel free to update with valves you use.

Richard
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File Type: zip Sussex valve selection data.zip (7.0 KB, 241 views)
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Old 7th Feb 2014, 8:20 am   #1030
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi
I am very close to completing the construction of my Sussex Valve Tester. I have built my tester circuits using my own design veroboard layouts. For the HT sections I used alternate copper strips and pealed off the ones not used to improve the insulation. Each module was tested as it was constructed and problems corrected. I am now considering the best way to carry out final tests on everything and commission the tester, for this I plan to follow the "Commissioning" notes in the manual.

I would like to hear from anyone if they have additional advice on issues to look out for as I don't want to end up damaging the mains transformer.

thanks
Mike
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Old 7th Feb 2014, 9:00 am   #1031
KeithsTV
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Default Re: The "Sussex" Homebrew Valve Tester.

Mike

The notes are a very good way to proceed when commissioning your tester. A scope would be useful to check the oscillator output but is not essential.

I'd be interested in your experience of commissioning your Sussex and any pictures for inclusion in the manual I am compiling.

The manual project is proceeding fairly well, only being interrupted by cars needing repairs, decorating my daughter's bedroom and other domestic issues. I hope to have a draft copy ready for Golborne in April for people to comment on.

Keith
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Old 7th Feb 2014, 9:57 am   #1032
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi
I have come across an issue with the first stage of the "commissioning tests".
I have built my tester with a patch bay rather than a multi way switch for each pin.
So on my tester when I check resistance between the cathode and all other electrodes there is a permanent 21k connection between the cathode and the screen grid, through R23 R24 & R33. Do you see this in itself being a problem.
I have drawings of my veroboard layouts which I can supply.
I will post some photos of the work so far.
Thanks
Mike

More photos to follow
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Old 7th Feb 2014, 10:25 am   #1033
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Default Re: The "Sussex" Homebrew Valve Tester.

Here are some more photos.
I found that the voltage stability of the LV heater supply was not very good with varying loads. This was discussed on the Vrat forum and an alternative circuit was used for the low volt heater supply, see drawing, this required a new heater switch. (ebay item 200298151557) I drilled and added a screw to create a new end stop for the 7th switch position.
A green LED was used in preference to a 2.7v zener, the feed resistor was chosen for the correct output voltage at 1.45v with a load of 25mA.
The diode in the LED circuit is shorted to give 2.1v. I used a TIP3055 from the spares box for the transistor.
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Last edited by crackle; 7th Feb 2014 at 10:45 am.
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Old 7th Feb 2014, 1:36 pm   #1034
KeithsTV
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Default Re: The "Sussex" Homebrew Valve Tester.

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Originally Posted by crackle View Post
So on my tester when I check resistance between the cathode and all other electrodes there is a permanent 21k connection between the cathode and the screen grid, through R23 R24 & R33. Do you see this in itself being a problem.
Those resistors are in the control grid (G1)circuit and shouldn't be connected to the screen grid or anode. Is it possible that the gas test relay, RL3, has been wired incorrectly or the bane of any veroboard user a track has not been completely cut (been there done it got the T shirt and seen the smoke)?

Keith
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Old 7th Feb 2014, 2:07 pm   #1035
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Default Re: The "Sussex" Homebrew Valve Tester.

Sorry, my mistake I should have typed "control grid" which had a resistance of 21k to the cathode.
Mike
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Old 7th Feb 2014, 2:59 pm   #1036
KeithsTV
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Default Re: The "Sussex" Homebrew Valve Tester.

Ah that's OK then. I'd be worried if there wasn't a resistance between the control grid and cathode.

Keith
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Old 7th Feb 2014, 3:04 pm   #1037
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Default Re: The "Sussex" Homebrew Valve Tester.

yep - circuit is R23 and R24, both 10k resistors which will take the control grid down to ground if you measured that path.
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Old 7th Feb 2014, 4:22 pm   #1038
crackle
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Default Re: The "Sussex" Homebrew Valve Tester.

My initial tests are all good. I am still waiting on some relays to be delivered, (for some reason I originally bought 24v relays ).
For testing I have had to put in some temporary patch wires to simulate the relay contacts.
I have 0 to -43v on the grid circuit and have set the AC volts to 100mv. With a signal tracer (simple transistor audio amp) connected to grid and ground the tone comes on quickly, but the voltage takes about 30 seconds to stabilise at 100mv.
The anode and screen selectors go from 0 to 300v. I connected a 10k 5w resistor between A1 and cathode and was a little puzzled why the current was not showing correctly at 20mA when volts were set to 200v. (it showed something like 18mA)
Then I remembered there was a little pre-set on the meter, I adjusted this to read 20mA.
The heater voltages are all correct.
I have not tested any of the built in test functions such as gas, heater con. heater K short, or push for 50mA.
But it all looks good, I am very excited, cant wait for the relays to be delivered and test my first valve.
I must say that this project is by far the most complex electronics I have tackled, I found it mind numbing during the wiring up of all the parts. Maybe I would have had an easier task if I had obtained the printed circuit. But then, I think I feel more satisfied knowing I have designed my own circuit boards and assembled everything myself.
I have been working on this project more or less solidly since Christmas. I did however start it last year, cant remember exactly when now, but abandoned it until I could afford the custom made transformer from Ed.
In the process of assembling the veroboard circuits I made various little changes to the layout. I will check these and update the drawings to try and get them correct.
When I have done this I will send my circuit board drawings in.
Mike
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Old 7th Feb 2014, 11:07 pm   #1039
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Mike, it's looking good, glad you enjoyed the challenge. Note that you set up using a resistor may only be totally accurate as a power resistor may only be a 5% part, it would be better to use the resistor with a current meter connected in series to set the calibration.

Ed
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Old 8th Feb 2014, 7:11 am   #1040
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello Ed
Good idea, I have now recalibrated as you suggested with my DMM in series with the anode load and it did need a little further adjustment.
Thanks
Mike
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