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Old 18th Apr 2011, 8:17 am   #561
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello All,
I have obtained some push button switches from Sourcing Map in Hong Kong to use instead of the rotary switches to make a more compact top panel layout.
These are the larger KSA2 type. I wonder if anyone has used these, as the rating seems to be 500mA continuous current rating which would appear to be low for the heater. I can't see any way of switching the heaters by a relay without using a bank of relays, unless I'm not seeing the obvious answer (which is quite possible)
The switching current is of course much less, but that should not be a problem as you wouldn't alter the switches once set up.Any ideas would be welcome

Regards
Mike
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Old 18th Apr 2011, 12:07 pm   #562
Brian R Pateman
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Default Re: The "Sussex" Homebrew Valve Tester.

The switching currents are usually quoted for make / break on load. If you set up the connections with no power applied (as per AVO valve testers) the current rating doesn't matter as much.
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Old 18th Apr 2011, 10:24 pm   #563
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Default Re: The "Sussex" Homebrew Valve Tester.

Brian,
thanks for the reply, I am not so worried about the switch contact, more by the size of the PCB track connecting the pad of the switch to the connecting pads on the rear of the switch. I would estimate they are at best 0.5mm wide.

Mike
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Old 24th Apr 2011, 7:50 pm   #564
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Smile Re: The "Sussex" Homebrew Valve Tester.

Hi everyone. I´m new in this forum. But this project (valve tester) is one I have been looking for quite some time, but no success, until now!
So I think I will start build this valve tester asap.
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Old 25th Apr 2011, 8:47 am   #565
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi,
Welcome to the forum. You will find a wealth of information on building the Sussex as several have been built, looking very professional in appearance. As far as I can remember, no bad problems have been found with the original design, several have added additional features. Martin has ,I think, some PCBs left and Ed will still wind you a transformer.
My prototype is still going strong, and touch wood, hasn't had any problems.
Good luck with the build, you will find it very rewarding.
There is plenty of help out there should you hit problems

Regards
Mike
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Old 25th Apr 2011, 6:51 pm   #566
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Default Re: The "Sussex" Homebrew Valve Tester.

I still have an issue with the leakage LED which I believe is due to gas in the valve under test. I recently acquired seven NOS 6CH6's of which six tested fine. The target figures being 40mA Ia and a gm of 11, all gave around 37mA and a gm of 11-12 except one valve. It gave a gm of 14 and an anode current of 55mA! The leakage test gave no indications either before or after testing. I decided to leave the valve heaters on for a while to see if there were any changes. The Ia dropped a little to 51mA but when returning the test switch to Heater Continuity, the Leakage LED glowed quite brightly for a while, then dimming. The condition seemed to be made worse if I used the Gas switch which showed a reading that slowly decreased with the same rate of brightness decrease on the leakage LED. Obviously this is being caused by a defect in the one valve though I have had this effect on other valves in my collection even though the test parameters of Gm and Ia were correct. Modelling the leakage circuit shows that the following leaks/LED currents are 1M/4.2mA, 5M/2.57mA, 10M/1.39mA, 25M/0.44mA. By lowering the 820k resistor to 33k should reduce the sensitivity to 1M/4.27mA, 1M5/2.63mA, 2M/0.9mA, 2M5/0.5mA. I have not tried physically lowering the resistor yet but thought I would ask anyone with the Sussex if they have had any similar problems or do I have a phantom wiring error?
It is some consolation I suppose to say that with the Leakage LED glowing after a Gm Test, pulling the suspect valve from the tester causes immediate extinguishing of the Leakage LED. So pretty certain the valve is causing the condition.
Regards, Les
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Old 26th Apr 2011, 11:32 am   #567
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Default Re: The "Sussex" Homebrew Valve Tester.

Les
i haven't come across this problem with mine, however, I do have access to a VCM163 which I could test the valve on for you.
Maybe someone nearer to you has similar facilities.

Mike
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Old 14th May 2011, 4:18 am   #568
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Default Re: The "Sussex" Homebrew Valve Tester.

I'm nearly there, at long last the parts have started to arrive and my checklist is almost complete.

I have learned a lot from reading this thread (several times) and have incorporated several of the ideas into my intended build.

The design is great and I'm really looking forward to getting it done, but I wondered if a 'Noise Test' facility would complete the project.

Several high end Hickoks have this and it seems to be the only thing missing from the 'Sussex'.

Is it worth while ? If so could someone suggest how it could be implemented ?

Soldering Iron at the ready - lets go
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Old 14th May 2011, 10:37 am   #569
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Default Re: The "Sussex" Homebrew Valve Tester.

Sorry me again

I'd like to use the full range of voltages from the original AVO CT-160.

How much work would this be ? Could someone point me in the right direction ?

Thanks in advance...
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Old 16th May 2011, 1:14 am   #570
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Default Re: The "Sussex" Homebrew Valve Tester.

To follow the CT160 faithfully you would have to increase the HT from 300V to 400V which may be possible by adding more zener diodes in the pre-regulator circuit but component ratings will have to be checked out. An alternative transformer will have to be used to get the 400V unless you can wire a suitable additional transformer in series with the present 'Sussex' secondary winding. Then it is a case of fitting suitable resistors in the selector switches, I have attached a typical example using 1mA as the network current.
If you could source a couple of 20 way switches you could cover all eventualities as in the VCM163.
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Old 16th May 2011, 3:43 am   #571
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Default Re: The "Sussex" Homebrew Valve Tester.

Thanks TopCap,

I agree with you. Looking at the circuit I think all I need to do is the following.

1. Use a transformer with a 0-300v secondary.

2. Change the Zener string to be 8 * 47v plus 1 * 24v, total = 400v.

3. Change the resistor values on the voltage selector switches to match the voltages available on the CT-160. I think the ratio used is 3K ohm per volt. (Much better explanation can be found in your diagram above -thanks)

4. Change the Cap C13 to have a rating of 600v.

I am not using the purpose built transformer, so the additional voltage is not a problem at this stage.

I guess I should give this a go and I'll report back with my findings.

Thanks !

Last edited by Mr_Klaatu; 16th May 2011 at 4:00 am.
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Old 21st Jun 2011, 12:44 am   #572
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Martin, someone suggested I look into building a tester like this myself as the avos etc are out of my price range.
I assume this is the one he was referring to as he mentioned pcbs being available too.
Do you still have any left, by chance?
It seems to be the part that would be trickiest for me to get otherwise,
Thanks,
Kevin.
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Old 23rd Jun 2011, 12:46 am   #573
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Kevin,
Sorry I can't send you a Private Message.
Yes, still 9 bare undrilled PCBs left @ £10 ea. inclusive and I've built (except for fitting the MOSFETs and Veropins) and set up the oscillator on another 9, but still been too distracted/lazy to work out a fair price yet or to build myself a complete valve tester.
Regards,
Martin
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Old 24th Jun 2011, 3:35 pm   #574
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Default Re: The "Sussex" Homebrew Valve Tester.

Yes, I don't seem to have priveleges yet to pm anybody here.
Thanks for reply - I could paypal you the £10 quite easily if you accept that.
The other 9 - how difficult would you say this project is for someone with limited experience? I'm up for a challenge and would enjoy the learning process... How much could you guess the rest of the stuff would cost?
Also, I have a soldering iron etc, a small vice (but not proper bench), a multimeter, pliers, strippers - not sure what else specifically.
Regards,
Kevin.
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Old 25th Jun 2011, 2:08 pm   #575
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Default Re: The "Sussex" Homebrew Valve Tester.

This should be a quick one !

Just how much heat do the BUZ80's generate ?

I see a lot of you have gone for some heavyweight heatsink's, after using your Sussex have you found heat to be a problem ?

I was looking to get a couple of standard TO-220 heat sinks off eBay for mine, is this going to be okay ?

Thanks in advance !

Last edited by Mr_Klaatu; 25th Jun 2011 at 2:09 pm. Reason: spelling...
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Old 25th Jun 2011, 4:03 pm   #576
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Default Re: The "Sussex" Homebrew Valve Tester.

Well I guess it really depends what valve your testing and for how long it is left on test for. As a worse case scenario with Anode and Cathode short circuit the dissipation in TR2 would be approximately 300V X 0.11 A = 33 Watts. Heat sinks usually are rated with degrees rise in temperature per Watt.

I went for a fairly chunky Heat sink as I am very capable of somehow inadvertently creating a Anode Cathode short.

Frank
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Old 29th Jun 2011, 11:24 pm   #577
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello All,

If anybody out there is contemplating implementing the CT160 tester voltages (i.e. 20 of them) and is looking for two (cheap) 20 way switchs...

I haven't found a cheap 20 way switch, but I've found some single pole 23 way ones on Ebay.

From the sellers blurb:

The auction is for a set of 4 pcs. 1 pole 23 positions rotary switches. Made in Ukraine in 1980's. Switches are in mint condition, never used. The body is made of hard composite carbolite material. Silver plated contact terminals. Shaft diameter is 6 mm. These switches are Make-Before-Break (shortening) type.

I've bought 4 from the Ukraine for $9 + $16 international p&p.
If anyone is interested, I'll post a follow up when they arrive.

Regards,

Bodge99.
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Old 30th Jun 2011, 8:22 am   #578
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Default Re: The "Sussex" Homebrew Valve Tester.

Bodge99, please post a follow up I have been interrested in these switches too but I have ended up buying Russian ceramic rotary switches from a few different sellers on eBay. I have been very satisfisfied with all of the different types of switches that I have bought from these Russian sellers on eBay, the price/quality ratio is better than anything I can find anywhere - and finding ceramic switches from most distributors these days is almost impossible.
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Old 9th Jul 2011, 1:54 pm   #579
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Default Re: The "Sussex" Homebrew Valve Tester.

Hello All.

As promised, a follow up on the switches purchased from the Ukraine.

They arrived yesterday, very well packaged in a stout cardboard box with polystyrene inside.

The photos show the overall size, with picture 3 indicating the switch contacts. These are 3 spring steel wipers.

It appears to be trivial to drill a small hole and add an extra stop at position 21 to convert these switches to 20 way.

I'm very pleased with the quality of these switches and intend buying some more for stock.

Regards,

Bodge99
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Old 28th Jul 2011, 12:12 pm   #580
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Default Re: The "Sussex" Homebrew Valve Tester.

WOW, over 66,000 views for what a project that I thought may be of interest to a few members of the forum. I'm gobsmacked to say the least.
How many are actually up and running, I would be interested to know.
Many thanks to those who have taken the time to view my idea, and to Martin and Ed who have helped with the PCBs and transformer.

Regards

Mike
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