Be aware that the toroidal bolt in my build is insulated at the other end so that there is no risk of earthing both ends. If the bolt is earthed at both ends, then it will behave a s single turn winding. Although the volts will be low, the current will be high in the short circuit. This can damage the transformer.
Thank you for this. I have been mulling over starting a YT channel of my own working with tube circuits and antique radio, but I have limited experience with both. Once I get a lab bench set up this will become my retirement project. Thanks for the clear explanation for how gm is measured. Didn't realize it was so simple.
Thank you for the comment. I have limited experience too, but I'm sharing my journey. I've learnt lots from the comments and it's good fun. Definitely go for it.
I also built Grant's tester and included my own changes. I removed the opto couplers for the meters and simply left the batteries in the two meters. I broke into this battery circuit and brought the wires out to a switch. When I use the tester I simply switch on the "meters" switch. There is no sign of the batteries dying. When they do it is a simple matter to open the case and change them. I also used a separate transformer for the heaters but included a rheostat to adjust the heater voltage to 6.3V. I haven't used the separate banana sockets but I am able to monitor various voltages via the sockets that are not in use. I have tested plenty of valves including 12A*7, 6L6, EL84, EL34,6V6, KT88 etc and have found a few with internal shorts and a few with low gm.
You may be surprised how much demand there is for Valves/Tubes these days, especially old stock from the Tube era. Valve/Tube amps have come back into fashion again, and there are quite a number of people restoring/rebuilding old valve/tube TV's. A tester is an absolute necessity in my mind when working with this era of equipment.
I have sensed the increased demand. I do sell a few valves and rectifier valves are in demand along with quality audio valves. There are more people now like me who want to experiment with the cheaper TV valves.
@@FelixGarcia-x3i Yes they can be a rats nest of cables. Best to get some electronics experience first. It tends just to be capacitors that need changing, but the sockets on old tester can be worn too.
Great video, I built this same tester a while ago and had a joiner friend knock up the cabinet for me. I used separate transformers for the heaters and meters. In the end a valve tester is really just a load of power supplies. All worked nicely but I wanted more flexibility with the plate and screen voltages.. I recently looked at the Sussex tester but a little over the top for what I wanted. Another UA-cam design from M Caldeira had some great ideas too. I then pinched ideas from all three testers and “upgraded” to my own design which works well, I can measure screen current now. Good luck with the build.
I totally agree about the restricted voltage range. I have valves that need 100V on the screen and 250V on the anode. Since I am using banana plugs, I can patch in an external screen PSU. I have one planned with that offers 8V to 300V. I may put in a current meter too to measure screen current. I use this tester most days. Its a fantastic tool and I love using it.
The meter battery circuit is interesting. But I would take a second transformer with two secondary 9V windings (and FBR and Caps). Of course your solution is clever and simple but I don't like batteries in mains powered gear 🙂
The batteries are in the reference design by Grant Willis, not mine. I took them out and used separate mains supplies for the meters. I too don't like mixing mains and batteries.
I’ve built models similar to that, yours looks very nice. Just think if you put that 1000 pounds into a valve stock? Tube testers were the means to sell tubes and install confidence. If I were running a service business a good stock would be of the greater value. Everyone loves a good tube tester in their shop. I can see a real purpose if you are selling tubes and you want to match them. Good job!
Thank you very much for the feedback. I know some testers are £1000, but mine was much less and a lot of fun to build. I tend to buy valves and collections and sell the ones I don't need. The tester is useful for that and will pay for itself in the long run.
Is there a particular reason for the grid (g1) being shunted to ground by the Cap 100n? In addition to increasing internal capacity obviously. Thank you.
I am just about to build a tester myself made with the same reference circuit as yours. Since I work purely in audio amplification, I only need to test about 4 different valve types (6L6, El34, EL84, 12ax7). Getting a suitable transformer is not easy especially as I left the UK for Brazil. I was thinking of getting a used valve transformer from a Marshall that utilises EL34s (higher current than 6L6 I believe). I could not find a good and cheap source for panel meters, so I'm intending to use external multimeters via banana plugs.
Glad that you are interested in building a tester. It’s really worthwhile. You want big voltages there and so may struggle to get the current capabilities from a voltage doubler. You will need a meaty transformer at the front end. Another source of transformer may be an old analogue oscilloscope. These tend to have an HT output into voltage doubler cascade to get the 2500V needed on the tube and they are big units. The use of banana plugs has saved this tester for me as I can plug any heater voltages in directly to the tube and also, I have trouble setting screen a voltage different from the plate voltage. Again, using an external power source via the banana plugs has saved me. I will be building a lot of modular add-ons to this tester to overcome these limitations and they will use a multimeter in place if dedicated meters.
@@VintageandReclaimedElect I am a novice at valves, like you my background is digital (I was senior engineer at Roland UK). I am repairing a lot of Fender, Marshall, Mesa Boogie, Laney etc guitar valve amplifiers at the moment, and because valves are so expensive, am going more for NOS valves like Panasonic, RCA etc. It would make sense to buy a used Fender or Marshall mains transformer which can supply voltages to 6L6, EL34, EL84 12AX7 etc. Even broken valve amps are expensive here in Brazil but it would be good to include a simple class A output stage so I can hear the valves! Do you think I am on the right track? I was tempted recently to buy a used Hickok TV3 tester, but it was about 600 quid and a bit overkill, plus didn't seem to test EL34 or 12AX7.
@@delatronics3257 Yes, home build will get get you exactly what you want. I built this as the decent testers were about £600 - £1100. Final build costs for this was about £280. I do need to build some extras though. If you see the right transformer, grab it. The idea of a class A output stage sounds good.
No reason as such, but you really need to accurately measure the 1V differential to calculate GM. I know some constructors have used analogue meters so really your choice. Thanks for the feedback
The highest voltage available seems a bit low for some tubes. I was lucky enough to pick up a basic emission tester for less than $50 that just needed a couple of high voltage caps but it's mostly good/bad but can give you some relative strength measurements. I'm curious why they started with such a low voltage transformer. Safety-wise, the tester I have is a steel box with no ground and neutral on the chassis so that adds some excitement!
Yes, it is too low of voltage for some valves, but perfectly fine for my valves. I did debate this in video 1 as I had a transformer that pumped up the voltage to 300V. Ideal for some audio vales, but I wanted to get more usable voltages for my collection. I needed 250V tops, 170V ad 90V. It takes about 10 mins to change the transformer if I need to. Great that you found a tester for $50. I’d be wearing rubber gloves if I used it - too scary!
If you need more voltage, you can add more multiplier stages and use the same transformer as well. Valves/tubes don't need a lot of current usually (other than the heaters). Obviously if you are testing high power valves/tubes then a beefier transformer would be required. This circuit is a good reference, but you'd just modify it to suit the valves/tubes you have in your collection, or in the equipment you primarily like to work on.
I'm not sure what direction to take that channel or whether I should keep it going. I unlisted the Android development material as they deprecate stuff so fast and I want it to be relevant. I switched to Arduino and other microcontroller controller material and had very few views. So not sure where to go with it.
You should be able to download the schematic of my version of this tester here. github.com/ghallberg-nbtt/vintage_stuff/blob/main/my_version_schematic_tube_tester.jpg. Unless stated, the diodes are 1N4007. The fuse needs to be 500mA rather than 250mA. Be sure to check out Grant Willis' reference design. valveheaven.com/2015/03/an-inexpensive-easy-to-build-diy-valvetube-tester/
Be aware that the toroidal bolt in my build is insulated at the other end so that there is no risk of earthing both ends. If the bolt is earthed at both ends, then it will behave a s single turn winding. Although the volts will be low, the current will be high in the short circuit. This can damage the transformer.
Thank you for this. I have been mulling over starting a YT channel of my own working with tube circuits and antique radio, but I have limited experience with both. Once I get a lab bench set up this will become my retirement project. Thanks for the clear explanation for how gm is measured. Didn't realize it was so simple.
Thank you for the comment. I have limited experience too, but I'm sharing my journey. I've learnt lots from the comments and it's good fun. Definitely go for it.
I also built Grant's tester and included my own changes. I removed the opto couplers for the meters and simply left the batteries in the two meters. I broke into this battery circuit and brought the wires out to a switch. When I use the tester I simply switch on the "meters" switch. There is no sign of the batteries dying. When they do it is a simple matter to open the case and change them. I also used a separate transformer for the heaters but included a rheostat to adjust the heater voltage to 6.3V. I haven't used the separate banana sockets but I am able to monitor various voltages via the sockets that are not in use.
I have tested plenty of valves including 12A*7, 6L6, EL84, EL34,6V6, KT88 etc and have found a few with internal shorts and a few with low gm.
Thank you for the comment. I'm glad you are using Grant's design. I have some modular improvements planned for mine.
You may be surprised how much demand there is for Valves/Tubes these days, especially old stock from the Tube era.
Valve/Tube amps have come back into fashion again, and there are quite a number of people restoring/rebuilding old valve/tube TV's.
A tester is an absolute necessity in my mind when working with this era of equipment.
I have sensed the increased demand. I do sell a few valves and rectifier valves are in demand along with quality audio valves. There are more people now like me who want to experiment with the cheaper TV valves.
I'm currently looking for one. Have seen some at auction sites but since I'm new to this kind of overwhelming to try and restore one
@@FelixGarcia-x3i Yes they can be a rats nest of cables. Best to get some electronics experience first. It tends just to be capacitors that need changing, but the sockets on old tester can be worn too.
Many such cases
Great project and something I need for my own repair work. Can't wait to see it through.
Thank you for that feedback. I am working on some add ons to improve it. Look out for those.
Great video, I built this same tester a while ago and had a joiner friend knock up the cabinet for me. I used separate transformers for the heaters and meters. In the end a valve tester is really just a load of power supplies. All worked nicely but I wanted more flexibility with the plate and screen voltages.. I recently looked at the Sussex tester but a little over the top for what I wanted. Another UA-cam design from M Caldeira had some great ideas too. I then pinched ideas from all three testers and “upgraded” to my own design which works well, I can measure screen current now. Good luck with the build.
I totally agree about the restricted voltage range. I have valves that need 100V on the screen and 250V on the anode. Since I am using banana plugs, I can patch in an external screen PSU. I have one planned with that offers 8V to 300V. I may put in a current meter too to measure screen current. I use this tester most days. Its a fantastic tool and I love using it.
Thank you sir for the very useful video.
Thank you for the feedback.
Back in the 70s I was a TV repair guy
I had a tube caddy and a portable tube tester
I would love to have one of those testers, but people ant silly money for the good ones. I hope this video triggered some memories.
The meter battery circuit is interesting. But I would take a second transformer with two secondary 9V windings (and FBR and Caps). Of course your solution is clever and simple but I don't like batteries in mains powered gear 🙂
The batteries are in the reference design by Grant Willis, not mine. I took them out and used separate mains supplies for the meters. I too don't like mixing mains and batteries.
I’ve built models similar to that, yours looks very nice. Just think if you put that 1000 pounds into a valve stock? Tube testers were the means to sell tubes and install confidence. If I were running a service business a good stock would be of the greater value. Everyone loves a good tube tester in their shop. I can see a real purpose if
you are selling tubes and you want to match them. Good job!
Thank you very much for the feedback. I know some testers are £1000, but mine was much less and a lot of fun to build. I tend to buy valves and collections and sell the ones I don't need. The tester is useful for that and will pay for itself in the long run.
a used orange vt 1000 digital tube tester is 300$, ive been using one in the last ten years it's great.
Good to hear and glad you are working with valves.
Is there a particular reason for the grid (g1) being shunted to ground by the Cap 100n? In addition to increasing internal capacity obviously.
Thank you.
I left it in from the reference design. It will be doing some filtering, but I would expect you can do without it.
I am just about to build a tester myself made with the same reference circuit as yours. Since I work purely in audio amplification, I only need to test about 4 different valve types (6L6, El34, EL84, 12ax7). Getting a suitable transformer is not easy especially as I left the UK for Brazil. I was thinking of getting a used valve transformer from a Marshall that utilises EL34s (higher current than 6L6 I believe). I could not find a good and cheap source for panel meters, so I'm intending to use external multimeters via banana plugs.
Glad that you are interested in building a tester. It’s really worthwhile. You want big voltages there and so may struggle to get the current capabilities from a voltage doubler. You will need a meaty transformer at the front end. Another source of transformer may be an old analogue oscilloscope. These tend to have an HT output into voltage doubler cascade to get the 2500V needed on the tube and they are big units. The use of banana plugs has saved this tester for me as I can plug any heater voltages in directly to the tube and also, I have trouble setting screen a voltage different from the plate voltage. Again, using an external power source via the banana plugs has saved me. I will be building a lot of modular add-ons to this tester to overcome these limitations and they will use a multimeter in place if dedicated meters.
@@VintageandReclaimedElect I am a novice at valves, like you my background is digital (I was senior engineer at Roland UK). I am repairing a lot of Fender, Marshall, Mesa Boogie, Laney etc guitar valve amplifiers at the moment, and because valves are so expensive, am going more for NOS valves like Panasonic, RCA etc. It would make sense to buy a used Fender or Marshall mains transformer which can supply voltages to 6L6, EL34, EL84 12AX7 etc. Even broken valve amps are expensive here in Brazil but it would be good to include a simple class A output stage so I can hear the valves! Do you think I am on the right track? I was tempted recently to buy a used Hickok TV3 tester, but it was about 600 quid and a bit overkill, plus didn't seem to test EL34 or 12AX7.
@@delatronics3257 Yes, home build will get get you exactly what you want. I built this as the decent testers were about £600 - £1100. Final build costs for this was about £280. I do need to build some extras though. If you see the right transformer, grab it. The idea of a class A output stage sounds good.
I found this extremely helpful. is there any reason why I couldn't use analogue meters?
No reason as such, but you really need to accurately measure the 1V differential to calculate GM. I know some constructors have used analogue meters so really your choice. Thanks for the feedback
The highest voltage available seems a bit low for some tubes. I was lucky enough to pick up a basic emission tester for less than $50 that just needed a couple of high voltage caps but it's mostly good/bad but can give you some relative strength measurements. I'm curious why they started with such a low voltage transformer. Safety-wise, the tester I have is a steel box with no ground and neutral on the chassis so that adds some excitement!
Yes, it is too low of voltage for some valves, but perfectly fine for my valves. I did debate this in video 1 as I had a transformer that pumped up the voltage to 300V. Ideal for some audio vales, but I wanted to get more usable voltages for my collection. I needed 250V tops, 170V ad 90V. It takes about 10 mins to change the transformer if I need to.
Great that you found a tester for $50. I’d be wearing rubber gloves if I used it - too scary!
If you need more voltage, you can add more multiplier stages and use the same transformer as well. Valves/tubes don't need a lot of current usually (other than the heaters). Obviously if you are testing high power valves/tubes then a beefier transformer would be required.
This circuit is a good reference, but you'd just modify it to suit the valves/tubes you have in your collection, or in the equipment you primarily like to work on.
VERY interesting, but what is your camera doing all the time in and out ..
Motion tracking. I will turn it off!
A link to your other channel would be nice... I love to mix current and obsolete tech.
I'm not sure what direction to take that channel or whether I should keep it going. I unlisted the Android development material as they deprecate stuff so fast and I want it to be relevant. I switched to Arduino and other microcontroller controller material and had very few views. So not sure where to go with it.
Thanks for this vedio u Can share the schematic diagram
You should be able to download the schematic of my version of this tester here. github.com/ghallberg-nbtt/vintage_stuff/blob/main/my_version_schematic_tube_tester.jpg. Unless stated, the diodes are 1N4007. The fuse needs to be 500mA rather than 250mA.
Be sure to check out Grant Willis' reference design.
valveheaven.com/2015/03/an-inexpensive-easy-to-build-diy-valvetube-tester/