I wonder if something like this could be built using something like a PI or Arduino to set all the controls and send the result data out the serial port to an application on a computer that could print a report or graph showing the characteristics of a tube. On your computer just select the tube from a database and that info would be sent to the tester to setup the socket for the tube and results send back.
Those sort of valve testers have been developed and made by DIYers - a Google search will find them and I believe there are kits available that you can make.
Hi Richard, I was wondering how you made the filament supply? Is it just a transformer with secundairy windings from 0.75v - 110v? or did you did something else?
The tube manual is just the Avo VCM manual that is available for free download from places like BAMA manuals or Franks Tube data pages - it is easy enough to arrange the switches to operate the same as the Avo VCM's - to switch from side 1 to side 2 of dual valves just need to switch the grid from side 1 to side 2.
Hi! Nice build 👍🏻 Do you have a schematic or something about the improvements on the rat tube tester? I looked at the schematic, but there’s no gas test, and that h-k light, is that for the gas leakage test… the heater supply is improved also.. nice job
Gas test is just series resistor - around 0.5meg - on the grid lead, and a push switch to short the resistor, a gassy tube draws grid current, which will cause a voltage drop across the resistor, short the resistor and grid voltage will increase causing a change ( noticeable) in anode current. The original RAT circuit switches both the anode and grid when using the side 1/2 switch to test double triodes - this is fine if you only have a set of prewired sockets but if you want to add extra sockets and switches to accommodate them, the circuit needs to change slightly - the grid is connected to both sides of a double tube and only the anode is switched from side 1 to side 2, it is then possible wire the extra sockets and switches so the Avo data book can be used for switch settings, no need to work out your own. The bias voltage is measured between cathode and grid. The HK led on the rat tester is not that great not very sensitive, I was going to improve it but so far have not and I use my MKII Avo for shorts and HK leakage tests, the filament continuity circuit uses a current transformer to detect ac current through the filament wires, works from 50mA up uses a simple 741 op-amp to light the led
Hi Richard! Thnx for the message! I have a uTracer (based on tektronix 576) which is great matching tubes etc. My goal is to expand my tester to weed out bad tubes which can destroy my interface alsoThe uTracer is great for the last stage in testing tubes. So the rat tube concept is really cool! I want to strip all the pre-wired sockets, because i use switch matrix. I found a simple a simple leakage test (have no tried it yet) by placing a 82k resistor on the base of a mpsa42 and a 820k resistor to the emitter to turn on a led or neon when a with threshold of 5uA when grounding the grid, anode or cathode. I found a thread also about the sussex tube tester.. looks a-lot at the rat tube and have some cool options also.. Gotta work now, but i’ll be back haha
@@richardhughes8408 btw how did you made the filament supply? Is it ac or dc? Is it a multi tapped 120v transformer or did you used resistors or zeners? Or some kinda voltage regulator. Thnx
Hello Richard, very nice implementation of the RAT tube tester. Great job. I have a few questions regarding your version. The original project didn't show a BIAS voltmeter nor an Anode current meter. Did you connect the voltmeter between cathode and COM ground, and the anode current meter in series to anode tube terminal, or else? What is the RECTifier function? You did change the GM scale to 3/15 mA/V, because of your meter? And finally, on the Triodeeelectronics web site, there is a remark of a grid conduction warning LED. I could not find it on the schematic. Was this deleted or not implemented? Thanks.
I placed the bias meter between the grid and cathode, anode current meter in series with the the anode supply. Gm meter - the original RAT document called for a DMM to be plugged in - I first tried an Ebay digital 200mV AC meter but they start to get non linear below around 15mV and could be 10% out below 10mV so I made an AC millivoltmeter using a moving coil movement I had, that way I could make a paper scale, mark it off against a known accurate DMM to allow any for non linearity. Recifier function - I had ideas to also include rectifier testing but has not yet been implemented - maybe one day. Grid conduction LED - I searched but could not locate that document so you know as much about it as I do.
@@richardhughes8408 Thanks . For now, I'm going to install anode and screen voltmeters, digital 0-500V, BIAS voltmeter 30/60V digital and use an external FLUKE DMM for Gm/Mu measures.
@@c.k.b6840 This is actually the second RAT tube tester I built, the first was largely experimental as the RAT tester was to me a bit of an unknown, for the Gm meter in that build I used a diy AC millivoltmeter made up of a 200mV DC digital panel meter driven by an op-amp 1Khz band pass filter ( to filter out any unwanted mains hum) and an op-amp precision rectifier, there are plenty of precision rectifier circuits around on the internet - linearity was not too bad if you can find low fwd drop germanium diodes for the rectifier circuit, I had some OA79's which have around 250mV fwd voltage drop and linearity was good down to around 8-9mV. The original RAT tester used multi position switches for anode and screen controls - this is not a bad idea, it is good though to keep the anode and screen meters - they are a good indicators of an internal short in a valve - if you are turning up the anode volts but the meter reading is not going up then something is wrong - usually an internal short, moving coil meters are good here as they have a much quicker response than digital panel meters - also they don't need a separate power supply. The side 1/2 switch on the RAT tester switches the grid and the anode from side 1 to side 2 - I found you only need to switch the grid from side 1 to side 2 that way if you decide to expand things and include extra sockets with switched connections you can wire them so that the AVO data book can be used - saves a lot of looking up of individual valves data setting - it's all in the Avo data book already. Good luck with your project
@@richardhughes8408 This will be my 4th tube tester. I have a Triplett 3414 emission tester, a French PC tester (similar to uTracer) and uTracer. I don't have that many tubes, about 90-100, but I like test instruments. Currently I am searching for a proper enclosure and front panel for the RAT tester. Interestingly, Steve Bench in his application notes uses the cathode current, not Ia, for tube evaluations. Have you seen them? BTW, I have seen AC millivoltmeter circuits using Si diodes and Schottky diodes.
@@c.k.b6840 Over the years I've had many tube testers Eico, Triplett, Supreme, Avo, Taylor, Precision, currently I have only 6 left that will eventually make their way to Ebay, I'll keep the RAT tester, and old Confidence tester that is probably nudging 100yrs old - I like it's cast aluminium front panel that has a stove enamel finish and probably one of the Avo's - like you I like test instruments, but since downsizing and retiring I no longer have the room to keep them all. Yes, Steve Bench used cathode current which is ok for triodes but with pentodes the screen/G2 current would throw out the current reading slightly.
I used a diy PCB but strip board can be used, you may also to look at the diy valve tester over at the British Vintage Wireless forum, they call it the Sussex - it operates in a slightly different way, while I have tried it and it works well I prefer the way the RAT tester works - it is purely a personal preference - the Sussex tester is very popular and well documented on the forum - has been built by many forum members who are always very willing to help if you have issues.
I'm not 100% certain what you mean regarding the Gm meter, the moving coil meter on the right is an AC millivolt meter made up from a standard 1ma movement (salvage store buy) with a redrawn paper scale driven by an op amp precision rectifier - switchable gain provides 2 scales - a precision rectifier has a bridge rectifier in the feedback circuit, the actual schematic is not hard to find if you google precision rectifier, the front end of the rectifier has a band pass filter to filter out any 50Hz or 100Hz mains interference that inevitably finds its way in.
@@richardhughes8408 Thanks for your clarification. I didn't realize the paper scale was custom. I assumed (and hoped) the movement was available as shown, and I was going to ask for a part number. I'm in the process of designing my own flavour of the RAT tester. I like your idea to provide options for 50 mA and 100 mA of plate current. How does your design implement the gas test? My current plan is to have a 1Meg resistor in series with the grid, shorted out by a NC momentary switch, where pressing the switch puts the resistor in circuit, and the operator watches the transconductance measurement for changes. I'm not at the prototyping phase yet, but I'm undecided on whether to put this resistor before or after the inverter IC which provides the AC millivolt signal.
@@stevencraig It isn't hard to make a custom scale for a meter movement, I use Inkscape - free vector drawing software, once the rectifier/filter circuit is made up and working, hook it up to a sig gen and a known accurate millivoltmeter, remove the meter front glass/bezel remove scale (slide it off under the needle) and put it back on reversed then just mark the divisions on the scale with a pencil/marker while adjusting the output of the sig gen, remove the scale again and either scan or take a photo - import the photo in Inkscape and lock that layer - start a new layer and draw/design/trace over the top you can go a bit nuts here and include a custom name/logo. When you are satisfied, print, cut out and glue the new paper scale on. The other easier options are:- just get a 200mV digital panel meter from Ebay and drive it with a precision rectifier circuit OR get an AC 200mV digital panel meter, I was going to go down that route but found that they are non linear once the measured ac voltage gets much below 20mV this presents a small problem for ECC83's and similar tubes that have low Gm's, the measured voltage is 16mV but the non linearity of the meter displays this as about 12 or 13 mV, I already had the meter movement and I thought why not give it a retro/vintage look. I also used a resistor in the grid circuit and placed it after the IC.
Thanks for all the information. I don't have a sig gen yet, nor an accurate millivolt meter. I have plans to build both in the near future (I'm not sure I'll ever need anything with professional grade accuracy) so I'll save the custom meter scale for a project upgrade. I'm looking forward to it. I also really appreciate the tip about the AC meter nonlinearity. I'll definitely stick with DC and the precision rectifier.
@@stevencraig A decent digital multimeter is ok for millivolts and at a pinch you can get sig gen apps for mobile phones - good luck with your project.
75% of it is made up of recycled parts, sockets, switches, transformers etc, case is a recycled piece of medical gear so it is hard to say how much - certainly less than $100, if you have built gear yourself you will know that electronic components are cheap it is the hardware that costs
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I wonder if something like this could be built using something like a PI or Arduino to set all the controls and send the result data out the serial port to an application on a computer that could print a report or graph showing the characteristics of a tube.
On your computer just select the tube from a database and that info would be sent to the tester to setup the socket for the tube and results send back.
Those sort of valve testers have been developed and made by DIYers - a Google search will find them and I believe there are kits available that you can make.
Hi Richard,
I was wondering how you made the filament supply?
Is it just a transformer with secundairy windings from 0.75v - 110v?
or did you did something else?
You've done a grand job there and it has some very useful features, nice one....DA
Where did you find the tube manual you downloaded?
The tube manual is just the Avo VCM manual that is available for free download from places like BAMA manuals or Franks Tube data pages - it is easy enough to arrange the switches to operate the same as the Avo VCM's - to switch from side 1 to side 2 of dual valves just need to switch the grid from side 1 to side 2.
Hi! Nice build 👍🏻 Do you have a schematic or something about the improvements on the rat tube tester? I looked at the schematic, but there’s no gas test, and that h-k light, is that for the gas leakage test… the heater supply is improved also.. nice job
Gas test is just series resistor - around 0.5meg - on the grid lead, and a push switch to short the resistor, a gassy tube draws grid current, which will cause a voltage drop across the resistor, short the resistor and grid voltage will increase causing a change ( noticeable) in anode current. The original RAT circuit switches both the anode and grid when using the side 1/2 switch to test double triodes - this is fine if you only have a set of prewired sockets but if you want to add extra sockets and switches to accommodate them, the circuit needs to change slightly - the grid is connected to both sides of a double tube and only the anode is switched from side 1 to side 2, it is then possible wire the extra sockets and switches so the Avo data book can be used for switch settings, no need to work out your own. The bias voltage is measured between cathode and grid.
The HK led on the rat tester is not that great not very sensitive, I was going to improve it but so far have not and I use my MKII Avo for shorts and HK leakage tests, the filament continuity circuit uses a current transformer to detect ac current through the filament wires, works from 50mA up uses a simple 741 op-amp to light the led
Hi Richard! Thnx for the message!
I have a uTracer (based on tektronix 576) which is great matching tubes etc.
My goal is to expand my tester to weed out bad tubes which can destroy my interface alsoThe uTracer is great for the last stage in testing tubes.
So the rat tube concept is really cool! I want to strip all the pre-wired sockets, because i use switch matrix. I found a simple a simple leakage test (have no tried it yet) by placing a 82k resistor on the base of a mpsa42 and a 820k resistor to the emitter to turn on a led or neon when a with threshold of 5uA when grounding the grid, anode or cathode.
I found a thread also about the sussex tube tester.. looks a-lot at the rat tube and have some cool options also..
Gotta work now, but i’ll be back haha
@@richardhughes8408 btw how did you made the filament supply? Is it ac or dc? Is it a multi tapped 120v transformer or did you used resistors or zeners? Or some kinda voltage regulator. Thnx
Hello Richard,
very nice implementation of the RAT tube tester. Great job. I have a few questions regarding your version. The original project didn't show a BIAS voltmeter nor an Anode current meter. Did you connect the voltmeter between cathode and COM ground, and the anode current meter in series to anode tube terminal, or else? What is the RECTifier function? You did change the GM scale to 3/15 mA/V, because of your meter? And finally, on the Triodeeelectronics web site, there is a remark of a grid conduction warning LED. I could not find it on the schematic. Was this deleted or not implemented? Thanks.
I placed the bias meter between the grid and cathode, anode current meter in series with the the anode supply. Gm meter - the original RAT document called for a DMM to be plugged in - I first tried an Ebay digital 200mV AC meter but they start to get non linear below around 15mV and could be 10% out below 10mV so I made an AC millivoltmeter using a moving coil movement I had, that way I could make a paper scale, mark it off against a known accurate DMM to allow any for non linearity. Recifier function - I had ideas to also include rectifier testing but has not yet been implemented - maybe one day. Grid conduction LED - I searched but could not locate that document so you know as much about it as I do.
@@richardhughes8408 Thanks . For now, I'm going to install anode and screen voltmeters, digital 0-500V, BIAS voltmeter 30/60V digital and use an external FLUKE DMM for Gm/Mu measures.
@@c.k.b6840 This is actually the second RAT tube tester I built, the first was largely experimental as the RAT tester was to me a bit of an unknown, for the Gm meter in that build I used a diy AC millivoltmeter made up of a 200mV DC digital panel meter driven by an op-amp 1Khz band pass filter ( to filter out any unwanted mains hum) and an op-amp precision rectifier, there are plenty of precision rectifier circuits around on the internet - linearity was not too bad if you can find low fwd drop germanium diodes for the rectifier circuit, I had some OA79's which have around 250mV fwd voltage drop and linearity was good down to around 8-9mV. The original RAT tester used multi position switches for anode and screen controls - this is not a bad idea, it is good though to keep the anode and screen meters - they are a good indicators of an internal short in a valve - if you are turning up the anode volts but the meter reading is not going up then something is wrong - usually an internal short, moving coil meters are good here as they have a much quicker response than digital panel meters - also they don't need a separate power supply. The side 1/2 switch on the RAT tester switches the grid and the anode from side 1 to side 2 - I found you only need to switch the grid from side 1 to side 2 that way if you decide to expand things and include extra sockets with switched connections you can wire them so that the AVO data book can be used - saves a lot of looking up of individual valves data setting - it's all in the Avo data book already. Good luck with your project
@@richardhughes8408 This will be my 4th tube tester. I have a Triplett 3414 emission tester, a French PC tester (similar to uTracer) and uTracer.
I don't have that many tubes, about 90-100, but I like test instruments. Currently I am searching for a proper enclosure and front panel for the RAT tester. Interestingly, Steve Bench in his application notes uses the cathode current, not Ia, for tube evaluations. Have you seen them? BTW, I have seen AC millivoltmeter circuits using Si diodes and Schottky diodes.
@@c.k.b6840 Over the years I've had many tube testers Eico, Triplett, Supreme, Avo, Taylor, Precision, currently I have only 6 left that will eventually make their way to Ebay, I'll keep the RAT tester, and old Confidence tester that is probably nudging 100yrs old - I like it's cast aluminium front panel that has a stove enamel finish and probably one of the Avo's - like you I like test instruments, but since downsizing and retiring I no longer have the room to keep them all. Yes, Steve Bench used cathode current which is ok for triodes but with pentodes the screen/G2 current would throw out the current reading slightly.
Thanks for posting this! I'm going to make one of these for sure. Did you build it up on stripboard? I love the analog and digital panel meters!
I used a diy PCB but strip board can be used, you may also to look at the diy valve tester over at the British Vintage Wireless forum, they call it the Sussex - it operates in a slightly different way, while I have tried it and it works well I prefer the way the RAT tester works - it is purely a personal preference - the Sussex tester is very popular and well documented on the forum - has been built by many forum members who are always very willing to help if you have issues.
Ottimo lavoro,complimenti.
Well done. Which Gm meter are you using and where did you get it from? Thanks
I'm not 100% certain what you mean regarding the Gm meter, the moving coil meter on the right is an AC millivolt meter made up from a standard 1ma movement (salvage store buy) with a redrawn paper scale driven by an op amp precision rectifier - switchable gain provides 2 scales - a precision rectifier has a bridge rectifier in the feedback circuit, the actual schematic is not hard to find if you google precision rectifier, the front end of the rectifier has a band pass filter to filter out any 50Hz or 100Hz mains interference that inevitably finds its way in.
@@richardhughes8408 Thanks for your clarification. I didn't realize the paper scale was custom. I assumed (and hoped) the movement was available as shown, and I was going to ask for a part number. I'm in the process of designing my own flavour of the RAT tester.
I like your idea to provide options for 50 mA and 100 mA of plate current.
How does your design implement the gas test? My current plan is to have a 1Meg resistor in series with the grid, shorted out by a NC momentary switch, where pressing the switch puts the resistor in circuit, and the operator watches the transconductance measurement for changes. I'm not at the prototyping phase yet, but I'm undecided on whether to put this resistor before or after the inverter IC which provides the AC millivolt signal.
@@stevencraig It isn't hard to make a custom scale for a meter movement, I use Inkscape - free vector drawing software, once the rectifier/filter circuit is made up and working, hook it up to a sig gen and a known accurate millivoltmeter, remove the meter front glass/bezel remove scale (slide it off under the needle) and put it back on reversed then just mark the divisions on the scale with a pencil/marker while adjusting the output of the sig gen, remove the scale again and either scan or take a photo - import the photo in Inkscape and lock that layer - start a new layer and draw/design/trace over the top you can go a bit nuts here and include a custom name/logo. When you are satisfied, print, cut out and glue the new paper scale on.
The other easier options are:- just get a 200mV digital panel meter from Ebay and drive it with a precision rectifier circuit OR get an AC 200mV digital panel meter, I was going to go down that route but found that they are non linear once the measured ac voltage gets much below 20mV this presents a small problem for ECC83's and similar tubes that have low Gm's, the measured voltage is 16mV but the non linearity of the meter displays this as about 12 or 13 mV, I already had the meter movement and I thought why not give it a retro/vintage look. I also used a resistor in the grid circuit and placed it after the IC.
Thanks for all the information. I don't have a sig gen yet, nor an accurate millivolt meter. I have plans to build both in the near future (I'm not sure I'll ever need anything with professional grade accuracy) so I'll save the custom meter scale for a project upgrade. I'm looking forward to it.
I also really appreciate the tip about the AC meter nonlinearity. I'll definitely stick with DC and the precision rectifier.
@@stevencraig A decent digital multimeter is ok for millivolts and at a pinch you can get sig gen apps for mobile phones - good luck with your project.
Very nice home built tester how much did cost you to build?
75% of it is made up of recycled parts, sockets, switches, transformers etc, case is a recycled piece of medical gear so it is hard to say how much - certainly less than $100, if you have built gear yourself you will know that electronic components are cheap it is the hardware that costs
Could you build me one?
@@richardhughes8408 I will buy 20 sets if you can supply them. Please let me know. Thank you
@@MrMymodesty It's a one off - so sorry no can do.