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Old 12th Jan 2010, 12:34 am   #61
Philips210
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Default Re: Homebrew Valve Tester

An excellent project Mike, very professional.
I own an AVO VCM MK3 that is rather bulky compared to your design. When time permits, I'll have a go at building your circuit, it looks like a great project. I think that ferrite beads added to the valve base connections could be employed to minimise possible parasitic oscillations. This may be important as more bases are added.

Ed Dinning's suggestion of a separate transformer for the heater supply seems to be the best solution for a wide range of heater voltage requirements. Heavier duty switching may be required for the various heater ranges or separate wire jumpers could be employed.

Regards
Symon.

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Old 12th Jan 2010, 1:34 am   #62
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Default Re: Homebrew Valve Tester

I was hoping to use these switches, although the contact rating is given in the 100's of milliamps. it is also stated as being rated to 5 Amps.
Rather confusing but I was banking on the lower ratings as the breaking current and of course it is hoped that the switches would not be moved once set so can they be pushed to 5 Amps?
Les
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Old 12th Jan 2010, 1:43 am   #63
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Default Re: Homebrew Valve Tester

Les,

Care is needed with this type of switch. I have two here (no brand shown) which are superficially identical. However, one has MBB (make before break) contacts, the other is BBM (break before make). This initially caused me some confusion!

Edward
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Old 12th Jan 2010, 1:52 am   #64
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Default Re: Homebrew Valve Tester

Yes Edward, a local supplier here only does them as MBB and I nearly fell for those . I believe these are BBM, I have come across another Lorlin data sheet that seems to support my theory, i.e. will carry 5 Amps if uninterrupted.
Les

P.S. Yep, the 1024 is BBM with imperial shaft.
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Old 12th Jan 2010, 9:08 am   #65
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Default Re: Homebrew Valve Tester

Hi All,
further to the post regarding non availability of the LCD modules
http://shop.accessory4you.com/
list them as well as the address I originally gave

Mike
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Old 12th Jan 2010, 4:50 pm   #66
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Default Re: Homebrew Valve Tester

Thank you Mike !
Again, Ebay in France is restricting some Ebay shops. I can go to the shop but it list it as empty.... Funny guys !
I'm seriously considering making one ;-)
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Old 12th Jan 2010, 5:12 pm   #67
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Default Re: Homebrew Valve Tester

Hi Mike,
When do you think that a step by step guide will be available for the construction of your excellent project?

Thanks
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Old 12th Jan 2010, 6:08 pm   #68
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Hi Guitarist28 and others
The full details for the valve tester will appear in BVWS bulletin, although it must be said this is not a "blow by blow" account as much will depend on the casework and layout decided by each individual. Photographs of all salient points are included as are voltage measurements on the prototype.
There should be enough info on the forum to get things going, especially if Ed comes up with a transformer, which at the moment, general feedback suggests a single 6v heater winding will suffice. But there are still a few days for constructors to state their preferences.

Regards

Mike
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Old 12th Jan 2010, 9:47 pm   #69
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Default Re: Homebrew Valve Tester

Hi Gents, yes there is always the question of switch carrying and breaking ratings as well as MBB and BBM.
On a tester I built many years ago, I used a simple plug board. H&S may be a problem if you need 117 volts but 50 should just be "in".
If we believe that a few heater voltages are required for everyday work these could be 4.0, 5.0, 6.3 and 12.6. The latter at under 1 A but the others need to be up to 3 A for some big rectifiers. There could be external sockets, or a switch for an external heater supply for the many other voltages that are encountered.

Ed
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Old 12th Jan 2010, 11:23 pm   #70
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Default Re: Homebrew Valve Tester

I agree with that Ed, perhaps a fairly meaty secondary for those more hungry valves. To cater for the 1.4/2V directly heated valves, perhaps a rectifier and smoother fed by the 4V Tap and use a simple transistor regulator to switch it between 1.4 or 2V, the current would not be too much, especially the 1.4V types. I have very few battery valves but appreciate there are others who may have a special interest in these and would appreciate it. Obviously one cannot cater for all types, the range of heater voltages are too diverse so the option of a separate heater input is really a must. The transformer rating is complicated further by those wishing to have continuous running as an option in addition to just a quick test. Maybe the separate heater input terminals would also be a better option for continuous operation use.
Shrouds? If the transformer was visible perhaps, but for a piece of test gear an open transformer, with its cost reduction, would be quite acceptable here.
Les
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Old 13th Jan 2010, 10:14 pm   #71
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Default Re: Homebrew Valve Tester

Hi Les tyhe adaptor is a good idea, it could also cater for the popular 2.5V US valves beloved of the audio fraternity.

Ed
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Old 13th Jan 2010, 11:40 pm   #72
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Default Re: Homebrew Valve Tester

I personaly am going to concentrate on a few of valve base types that represent most of the useage in my collection of comms receivers. I like the idea of adapting for when there is the necessity to test more types, there are many easy ways of doing this. Nice and efficient on costs and complexity.

If you try to cater for all possibiliites there is a risk the transformer is going to price itself out of interest.

You know what it can be like sometimes the "what if's" can take over the design and turn it into something very expensive and complex for no real need.

Just my thought

Mike
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Old 14th Jan 2010, 12:42 am   #73
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Default Re: Homebrew Valve Tester

Does this tester have a name? "The Sword Valve Tester?"
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Old 14th Jan 2010, 6:04 pm   #74
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Default Re: Homebrew Valve Tester

Hi Graham,
Never thought about a name, I just call it the VT1 (not a sexy name I know) as it's the first one I've built, but if you want a name for the forum or other reason, call it what you like (within reason!!!), as I'm Sussex born and bred possibly something to do with that. I'll leave it up to you

Regards
Mike
PS Amazed at the number of views
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Old 14th Jan 2010, 8:38 pm   #75
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Default Re: Homebrew Valve Tester

'The Sussex VT' valve tester has a nice vintage ring to given the flavour of the forum.

I'm not suprised at the amount of replies that Swordholder has received given the resurgent interest in valves for all forms audio applications (including ipods)
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Old 14th Jan 2010, 10:53 pm   #76
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Default Re: Homebrew Valve Tester

Mike.

As far as the forums go it doesn't matter whether your design has a name or not. I was just thinking that if large numbers of these get built builders/owners might want to refer to them by a name. Just as we might say "I've got an AVO CT160" or "I've got a Taylor 45C", builders could say "I've got a Sussex" and other people in the know would know what they were referring to.

If you're happy with the name "Sussex Valve Tester" I'll add it to the thread title, or you might prefer another name?
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Old 14th Jan 2010, 11:03 pm   #77
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Default Re: The "Sussex" Homebrew Valve Tester.

Graham,
OK by me
Regards
Mike
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Old 15th Jan 2010, 10:22 pm   #78
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gents, I now have some lams for this transformer that I will try and get wound and sent off to Mike next week.
It looks as if it will fit on a 78 lam (95mm high, 80mm wide and a 40mm stack; about 70mm over the "belly").
It will have a 0-10-210-230-250 primary (110V can also be provided but as a different transformer).
0-250V at 120mA
0-30v at 20mA
0-6v at 50mA (times 3)
0-4-5-6.3 (@3A)-12.6v at 1A

I have yet to finalise the costing but this spec appears to be the minimum that is required. Inputs please.

For those who need a wider range of heater voltages I will look at an aux transformer, possibly about 2/3rds the size of the main one, which would have the heater voltages not supplied by the main unit. This would run from the 230V tap on the main transformer so that adjustment of the main input also sets the heater tranny.

Best regards, Ed
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Old 16th Jan 2010, 1:35 am   #79
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Default Re: The "Sussex" Homebrew Valve Tester.

Nice work ED

Mike
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Old 16th Jan 2010, 10:06 am   #80
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Ed,
The spec looks good, there are a couple of mods I have in mind for the future so could the 30v winding be changed to 35v @ 50mA.
Are you going to have tags on the trnasformer for connections, and will it be a frame mounting type so it can be mounted in different orientations
Thanks for the good work
Regards
Mike
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