DIY valve tester. [Archive] - The Art of Sound Forum

awkwardbydesign

09-12-2015, 12:54

I have a load of old valves, mainly ECC82, 83, 88s, and EL34s and EL84s. Some are quality (Mullard 8137 and 8136), some are not, but I have no idea of their condition.
So I googled "DIY valve tester" and eventually came up with this - http://www.valveheaven.com/2015/03/an-inexpensive-easy-to-build-diy-valvetube-tester/
It looks simple enough even for me, and I have transformers, HT caps, resistors, valve sockets and casework, so it won't cost much to build. I have ordered the switches and meters, so when they arrive (from China; could be January!) I can give it a go.
But before I start, does anyone have any views or advice on the circuit, or implementation? At the moment I plan to follow his plans, allowing for the need to use 2 transformers and older combined caps (470uF/400v + 800uF/250v common neg in a single can).
So any thoughts from anyone who actually knows what they are doing would be welcome. :D

Firebottle

09-12-2015, 17:46

Looks good to me Richard, build it as shown.

:)

awkwardbydesign

09-12-2015, 19:12

Thanks Alan, it looks simple enough even for me. As long as I connect everything this time.:doh:
I put a couple of unmatched Mullards in the Velleman, and although they worked, I have no idea if they match. So at least I could test that, even if the tester has no ultimate accuracy.

oceanobsession

10-12-2015, 22:46

I was looking at building this one , but then managed to drop on these testers for the right money they all work but each has a few probs me phil.

http://golbornevintageradio.co.uk/forum/attachment.php?aid=13311

awkwardbydesign

10-12-2015, 22:52

I was looking at building this one , but then managed to drop on these testers for the right money they all work but each has a few probs me phil.

Cool. But the thumbnail won't enlarge.

oceanobsession

10-12-2015, 23:13

Sorry dick , have put a link now , if your only interested in testing the common valves this diy tester seems great and gives you some idea of a valves quality , I was very interested in this , the dc voltages are very dangerous but I'm sure you know that , the avo testers are 2 mk2 and a mk1 , they are great things but require work , I shall keep them for a retirement challenge , they all seem to test valves ok but there are problems with rectifier valves which put a specified current to the valve i.e 6x5 valve is 30 ma
the current is dropped via resisters , the old bobbin type , but ive managed to test el84 ecc 83 82 81 ecc88 5687 with no problems . I love these old things they were
made to last . me phil.

Firebottle

11-12-2015, 08:26

Coo those look rather wonderful Phil.

Would you like some assistance with the repairs?

:)

awkwardbydesign

11-12-2015, 09:26

Never mind the valve testers, I want the lathe!

oceanobsession

11-12-2015, 15:40

Thanks for the offer of assistance but I think ive got my head around how these things work ,

awkwardbydesign

11-12-2015, 17:00

Oi! Get your own thread! :lol:

oceanobsession

11-12-2015, 18:13

sorry dick

awkwardbydesign

11-12-2015, 19:36

:lol::lol:

User211

11-12-2015, 21:43

I had a cool pic of a valve power amp made on a baking tin very much like that one. Can't find the pic...

Here's another, less pretty one. Baking tins. They're the future.

https://www.youtube.com/watch?v=h4gl1pTB96c

awkwardbydesign

11-12-2015, 23:01

I'm awfully tempted to do it that way. Here's a suitable one. http://www.iconiccollectables.com/sites/default/files/styles/product_thumbnail/public/product-images/117de4b206005056b707ed.jpg?itok=q9pSD-iY

User211

12-12-2015, 01:03

Kind of "My first valve tester" you mean? See if it's shitty on the kitty, kitty?

awkwardbydesign

12-12-2015, 09:45

Posted at 1am? Time for bed, methinks! :D

User211

12-12-2015, 09:58

I crashed on the sofa at about 11 then woke up. Off work til the NY though. Cool:)

awkwardbydesign

12-12-2015, 11:46

Off work until forever! Can get boring, so I come here to cause trouble. Must get the bike MOTed; who wants to live forever? http://www.focusedevents.com/monza-30-july-2016-european-trackday

struth

12-12-2015, 11:52

A few more years would be nice though;)

awkwardbydesign

12-12-2015, 13:24

Only if they're nice years!
Oh, one test meter arrived this morning (V and mA metering). Before I complained I checked my order; I only ordered one! :doh: Now ordered the other one. I think! :rolleyes:

Audio Advent

12-12-2015, 19:51

How about this one from Lampizator?

http://lampizator.eu/UPGRADE/tubetester/tester-8-2.jpg

Oh I forgot to draw the pot. It connects between the AAA cell stack - negative and the ground. The viper goes to tube grid. We also need interrupting switch because the pot (100K or 50K) will discharge the cells.

Of course instead of cells we can build own electronic supply of variable voltage from minus 5V DC to 0V.

Err, stick a plastic box over it when in use for safety! http://lampizator.eu/UPGRADE/tubetester/tester-1.jpg

http://lampizator.eu/UPGRADE/tubetester/tube%20tester.html

awkwardbydesign

12-12-2015, 20:05

How about this one from Lampizator?

http://lampizator.eu/UPGRADE/tubetester/tester-8-2.jpg

Err, stick a plastic box over it when in use for safety! http://lampizator.eu/UPGRADE/tubetester/tester-1.jpg

http://lampizator.eu/UPGRADE/tubetester/tube%20tester.html

Er, yes, I've seen that, but it didn't get my juices flowing. And I would like something I could actually move safely! I may one day Lampizate my Squeezebox Duet, that wouldn't move. :)

Arkless Electronics

12-12-2015, 20:35

They are both rather simple and limited... especially the second one!

awkwardbydesign

12-12-2015, 20:42

Ah, well so am I, so the one I'm making should be ideal. I just need to test the old valves I have, and I have lots of the bits already.

oceanobsession

12-12-2015, 21:41

Audio Advent

12-12-2015, 21:44

Er, yes, I've seen that, but it didn't get my juices flowing. And I would like something I could actually move safely! I may one day Lampizate my Squeezebox Duet, that wouldn't move. :)

Doesn't mean you have to make it exactly like that on a piece of board! If I'd only shown the circuit diagram then the thought of safety wouldn't have entered your mind.

What if the one you're thinking about had been mounted on a piece of wood would you reject that? :lol:

The Lampizator has the advantage of being simpler and not needing a second power supply for the .... err whatever the batteries are for. AND what I like about Lampizator is that he does things in his very "it's so simple! Just do it like this on a piece of board and stop fussing and putting up barriers about having a case and everything being OCD perfect.. Just do it!" attitude. That appeals to me.

Audio Advent

12-12-2015, 21:45

They are both rather simple and limited... especially the second one!

Depends what you want it for I guess. Simple checking if the valves are ok and halves matched is probably all most are looking for for tube rolling.

Arkless Electronics

12-12-2015, 22:03

Depends what you want it for I guess. Simple checking if the valves are ok and halves matched is probably all most are looking for for tube rolling.

Better than nowt but I'd want it to go up to 800V+ for power valves. Not much point testing a KT88 at 250V max.

awkwardbydesign

13-12-2015, 11:00

nice cheap English new colvern 10k pot for the bias voltage adjustment

(http://www.ebay.co.uk/itm/Poti-Widerstand-Potentiometer-Drahtpoti-Colvern-10-K-Ohm-/231576089161?hash=item35eb02b249:g:2IIAAOSwaNBUcGk p

There seems to be two versions of this tester , but the b9a socket will test everything I have , will you be buying the transformer he has listed , me phil.
I'm getting a cheap carbon pot from RS. Is that Colvern wirewound? I have a couple of transformers, one 6v and one 15v x 2. The trafo he lists appears to be available only in Australia. Cheap enough to buy, but expensive to post! It would have been cheaper to buy this pair on ebay. http://www.ebay.co.uk/itm/381109938701?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT and http://www.ebay.co.uk/itm/15VA-2-x-6-3V-heater-transformer-for-valve-amps-/171501575503?hash=item27ee4a5d4f:g:X2YAAOSwr81UPXJ a

awkwardbydesign

13-12-2015, 11:10

Doesn't mean you have to make it exactly like that on a piece of board! If I'd only shown the circuit diagram then the thought of safety wouldn't have entered your mind.

What if the one you're thinking about had been mounted on a piece of wood would you reject that? :lol:

The Lampizator has the advantage of being simpler and not needing a second power supply for the .... err whatever the batteries are for. AND what I like about Lampizator is that he does things in his very "it's so simple! Just do it like this on a piece of board and stop fussing and putting up barriers about having a case and everything being OCD perfect.. Just do it!" attitude. That appeals to me.
Negative bias on the grid?

Depends what you want it for I guess. Simple checking if the valves are ok and halves matched is probably all most are looking for for tube rolling.

Better than nowt but I'd want it to go up to 800V+ for power valves. Not much point testing a KT88 at 250V max.

Lukas' circuit is too basic for me. I think he threw it together in about an hour from bits he had in his pocket!
And testing what I have is the main reason for building the tester, plus the design AND layout have been tested, it seems. Also I have most of the "expensive" bits. Just not a suitable baking tray. :)
If I start getting fussy, I would want to test 845 DHTs too, as I have a couple left over.

Arkless Electronics

13-12-2015, 11:17

Remember, the baking try is critical! :D

awkwardbydesign

13-12-2015, 14:56

Damn!

awkwardbydesign

13-01-2016, 15:11

Well, it seems to work! I had to buy 2 cheap multi-meters, 2 x 470uF/100v caps, 4mm sockets, 4 switches, 1 x 15v+15v trafo, opto couplers, diodes, resistors, neon, and some fuses. Total cost, £30-£40. I had the rest of the stuff, including some big old caps which needed reforming, but I have a variac, so I just wound the voltage up slowly; seems to have worked.
The transformer http://www.ebay.co.uk/itm/400911751770?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT is really a 220v primary job, so I was getting 295v on the anode instead of 250v. And the 2 secondaries are poorly matched! I disconnected the last cap in the voltage multiplier, and now get 250v. But instead of the 250/180/125/90v in the original design, I now get 250/200/125/100v, which should do. I can always add a switch to get the 295v back if I want, plus a switch to flick between the 2 halves of twin triodes; at the moment I have to unplug and replug the 4mm leads.
I have only tried it with several Chinese 12AX7s, and initially couldn't get one side to measure properly. Then I realised I hadn't swapped the grid leads! :doh: Seems OK now, so next I will have to try the Mullard ECC83s and all the EL34s. And work out what the readings actually mean!
At least I can now see if any of the valves are faulty, and match them.
Onwards and upwards!
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160113_144006_zpso8hggfhq.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160113_144111_zpsrowcpps6.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160113_144240_zpspxi7zsos.jpg

Firebottle

13-01-2016, 19:33

Excellent - I might just make one myself.

:)

awkwardbydesign

13-01-2016, 20:42

I'll probably be asking you how on earth to use it!
The next stage will be to put some insulated sockets at the back for the unused plugs. At the moment I have to slide sleeves over them. And then double up the live anode, grid and cathode sockets on top so I can leave both sides of double triodes plugged in, and connect a switch to toggle between anode current readings.

awkwardbydesign

16-01-2016, 12:22

Anode voltage switch added, so I can use the last cap in the voltage multiplier, which gives me a choice of 250/295v. I bought 20 x 4mm sockets, so I doubled up the anode, grid, screen and earth sockets, and used the rest of them in an insulated row at the back, for storing the unused plugs. Decided not to add the switch to toggle between triode halves; it's just as easy to pull the plug.
Oh, and some photos of the insides, just to impress you with my neat wiring! This should really be finished now. I hope!
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Valve%20tester/20160116_115254_zpsjociokzv.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Valve%20tester/20160116_115401_zpsyms27k3b.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Valve%20tester/20160116_113927_zps9tpygwao.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Valve%20tester/20160116_113959_zpsmkwmrwon.jpg

tiguan

17-01-2016, 06:46

Congrats. Very good build indeed. If you are using all valve setup to check in time, it is very usefull. On the other side I was always in doubt when I buy a valve, if the figures the seller wrote are correct or not especially for far east countries.

Audio Al

17-01-2016, 06:51

You clever you are :)

awkwardbydesign

17-01-2016, 10:55

You clever you are :)

True. But not clever enough to avoid getting 250volts DC through my finger. :doh:

Firebottle

17-01-2016, 11:46

Ouch :eek:

DC stings doesn't it :mental: Fortunately I haven't had a DC shock for some decades, RF burn yes and that's different again.

:)

Arkless Electronics

17-01-2016, 12:43

Well done Richard!

Arkless Electronics

17-01-2016, 12:44

Ouch :eek:

DC stings doesn't it :mental: Fortunately I haven't had a DC shock for some decades, RF burn yes and that's different again.

:)

You a radio ham then Alan?

Firebottle

17-01-2016, 13:45

I am Jez, used to do fast scan amateur television (UHF and microwave) as well as radio but that has died a death.

:)

awkwardbydesign

17-01-2016, 15:12

Ouch :eek:

DC stings doesn't it :mental: Fortunately I haven't had a DC shock for some decades, RF burn yes and that's different again.

:)
At least I didn't burn 2 holes in my finger this, as I did with an undischarged 450v cap years ago!

Well done Richard!
Ah, now then, is that well done for making the thing, or well done for electrocuting myself? Is this one of those smiley moments? After the debacle of the smiley question, I am using as few as possible. http://theartofsound.net/forum/showthread.php?42390-Are-smilies-necessary
PS, don't take this seriously.

awkwardbydesign

09-02-2016, 18:27

Got another question. As the voltage is too high, I have taken the HT from the last diode, but removed the last cap, which gives me 245v. Can I insert (4 x 1N5404?) diodes to ground to lift the voltage by 5 volts? Taking anode current at 245v gives a false reading, as far as I can see.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Capture_zpsgf31f7qt.jpg

Firebottle

09-02-2016, 20:06

If you look at the valve curves the drop from 250V to 245V is going to make only a very small difference.

However removing the last cap in the voltage ladder will mean you have some AC on the supply voltage.
To reduce the voltage a little try a small value resistor in the connection from the HI LO voltage switch, that feeds C4, 6 and 8.

:)

awkwardbydesign

09-02-2016, 20:29

Ah, thanks. I'll try that. On a different note, I had this round on Sunday. http://www.bartola.co.uk/valves/2013/02/20/26-dht-preamp-gen2-by-rui-lourenco/ It made everything I've ever had here look silly. I was considering trying to make one, but then I woke up! :lol: It's a bit above my brain power, I fear.

awkwardbydesign

10-02-2016, 19:35

A 150 ohm resistor (measured at 154 ohms) in the feed to the caps worked for ECC83s. But of course the current limiting meant that EL34s only receive 240 volts! I guess a bigger transformer is called for, but that isn't going to happen. So for the moment I have a switch to bypass the resistor for the bigger valves, but I think I will order a 25w wirewound pot (preferably 200 ohms) and use that instead. I already have a little 300v digital panel meter on order, so I will be able to set the anode voltage precisely.
If I actually knew what I was doing, maybe I could attempt that DHT pre!

Firebottle

30-12-2017, 08:20

I thought this was a good project and have finally got around to knocking one up.

Because I have a multi tapped high voltage power supply and existing multimeters I have made it so these are external to the valve tester chassis;

http://i64.tinypic.com/wury1y.jpg

The impetus for getting this built was having failing ECC83's, out of 4 in the draw only one is a good one :doh: