0:01 sometimes life is well unpredictable and 0:09 sometimes things just seem to be the way they work supposed to be what you see on 0:18 the screen is a trace of a pentode 0:24 vacuum tube it is being displayed on a 0:30 Tektronix model 570 characteristic curve 0:36 tracer so what do those two have how do I know what time that was two together 0:43 well I wanted to return to I wanted to 0:53 wait one more video and I wanted to 0:58 return to electronics if I could as many of you know I've been off doing some 1:05 kind of wrapping up a review of my astronomy hobby and things like that but 1:13 my second love chronologically that is 1:19 was electronics I started out with astronomy and chemistry but because I 1:26 got a telescope and a chemistry set when I was 9 but by the time I was in middle 1:33 school they called it junior high back then electronics was the thing that I 1:38 loved the most and of course being in the 1950s that meant vacuum cubes well 1:47 Oh a couple of weeks ago my UPS delivery 1:53 man stopped me I was out in the front 2:00 yard as he was delivering something and said you're interested in vintage 2:06 electronics tubes and things like that aren't you and I said yes I wondered why 2:12 he how he knew that turns out he has delivered so much thanks to me that he 2:19 knew it and he also had a background in electronics he had worked for Raytheon 2:25 back in I think in the in the eighties 2:31 doing some electronics work and so he said you wouldn't be interested in an 2:37 old Tektronix curve tracer would you I mean my eyes lit up it was like you know 2:46 it would be like asking the Albert Einstein I'm no Einstein but like asking 2:52 Albert Einstein would you be interested in relativity yeah so he sold me this 3:00 curve tracer and I've been playing with it for the last week or so and so it is 3:06 I think fitting has a return a video 3:13 return to electronics and so you know if 3:19 I had to if I had to close out in on anything this would be it at any rate 3:25 enough about me in the history in my UPS man what this device does is it displays 3:35 various current and voltage characteristics graphically along the 3:42 the vertical axis it displays the current through the tube and along the 3:49 horizontal axis it displays the voltage in this case it's the play current verses play voltage and the 3:58 stamps are varying grid vote values so let me show you the block diagram of 4:06 this device and then come back and show you how it works a little bit and and 4:11 then we'll do we'll run a couple of tubes on it and see how it how it works 4:18 now it has a neat feature that it allows you to switch quickly between one tube 4:25 and another tube I'll save for later who of what those tubes are but these are 4:31 two pen toads that are being displayed and you see there's a difference in that 4:37 one and in that one though there's not a lot of difference notice that the top is 4:46 very close to the the top trace of this one so let's take a look at a block 4:53 diagram so here is the block diagram of the Tektronix 570 by the way this device 5:01 was built in 1955 I was 10 years old on 5:08 the left is a is the shaper for the 5:14 stepping voltage you remember you you saw that it would step the grid voltage it starts with this stepping voltage 5:23 shaper that feeds a step generator then 5:28 that is amplified by the step amplifier and can be applied to the grid of the 5:34 tube this is the device under test and there's space for two of these so that 5:39 you can switch between them well look at that a little bit later the so for the 5:48 display we just saw the step is applied to the grid the cathode is grounded the 5:57 plate is connected to the horizontal amplifier and also to the plate sweep 6:04 generator now the what the plate suite generator does it generates a a sweet voltage that can 6:12 go up to I think 500 volts on the 570 so 6:18 so it can be anything as little as 1 volt let's see it's the no 5 volts it's 6:27 the traditional Tektronix to 510 so it's 5 10 20 50 a hundred two hundred five 6:36 two hundred three hundred five hundred volts so it applies that to the plate 6:43 and then you can read out the plate through the horizontal amplifier while 6:49 the the current through the tube is 6:56 measured by the let's see vertical amplifier and the way it does that is 7:04 the current through the plate sweep generator is flows through this resistor 7:10 and so it taps the voltage off of that so this allows you to measure plate 7:15 current on the vertical while measuring plate voltage on the horizontal and 7:21 that's the display we just saw a minute ago so this is the basic diagram of the 7:28 five seventy so this is a printout from 7:34 the five seventy manual showing the 7:40 plate current versus plate voltage and 7:46 in this case this is for a six u 8 now a six u 8 is a two section tube it looks 7:58 like this 8:06 notice that one section is a triode and one section is a pentode let me let me 8:18 just pick that up and take it a little closer to the camera so that you can see 8:23 a little better what that looks like so you see that it's a yeah it's a triode 8:31 on the right and a pentode on the left these tubes were used in early 8:40 television sets to generate the vertical 8:45 sweep the triode section was used for the oscillator and the pentode section 8:52 was used to drive the yoke I'm not going to get into television Theory here but 8:57 basically that is the way that the the signal would be swept across the screen 9:02 from top to bottom there was also a horizontal sweep system that would sweep 9:08 it from left to right so what you see here are a series of stamps and on the 9:16 left are the setups for this so in the 9:21 manual one of the things that they part of the training of someone on using the 9:26 570 was to set up a 6u 8 and by the way it even I think originally came with a 9:33 68 tube fortunately I have some new old stock tubes and was able to dig up a 9:41 couple of 6u eighths but the basic idea 9:48 of this is it allows particularly a design engineer to measure the 9:57 characteristics on a particular type of tube it also allows someone to compare 10:03 the characteristics of two tubes for example suppose that you have a dual 10:11 triode like a 6s n7 where there are two triodes in the same package well you can 10:18 switch between those two using the switch that I used earlier and 10:23 compare to see how well matched they are so there were basically two applications 10:30 for this device one was for design engineers who were designing tube circuits to be able to find out the 10:40 characteristics of the tubes they were using so that they could design the 10:45 circuit around those characteristics and the second which has come into even much 10:51 more use these days is the matching of 10:56 tubes the because of the resurgence of 11:02 vacuum tube amplifiers both for guitars and for high fidelity the need to match 11:09 tubes particularly since you're dealing in many cases with new old stock tubes 11:15 that have been around for 50 60 70 years is finding a pair of tubes for example 11:22 that have similar characteristics so that they they don't require a lot of 11:30 imbalance in the amplifier to work correctly so for example in a push-pull 11:36 stage output stage and if you want to know more about that there are some 11:41 videos I did on how tubes work and and vacuum tube circuits that you might want 11:48 to look at at some point but at any rate these days these are used by places that 11:59 specialize particularly in tube electronics generally amplifiers to 12:05 match tubes and do other things for me I was just it's just a toy and I'm glad I 12:13 was able to acquire one of these it's almost like it was it was ordained here 12:22 you see the characteristics of a triode what we looked at just a minute ago was 12:29 the pentode section this a triode of a six gh8 - if you look on 12:40 the left at the pinout you see it is and I don't expect you to remember the six 12:46 u8 but take my word for it it is exactly the same pinout as the six you ate the 12:51 six gh8 was the replacement for the six you ate it had a little more 12:59 transconductance and could handle higher voltages so the six GH 8 and the six you 13:08 ate that we saw a minute ago are both medium mu triose mew just means the 13:16 amplification factor and a sharp cutoff pentode so these are what you would 13:27 display for the triode section of that same cube so let me show you a little 13:34 bit about how the 570 is set up and then we'll talk a little bit about how you 13:41 might use something like this though I will admit this is really just a boat 13:47 anchor okay there there is an application for it in in tube matching 13:54 for amplifiers but frankly there are solid-state versions of these kinds of 14:01 things that can be done and they work better because they work on a computer 14:06 so you can log the data and analyze it better and so on but for for a dinosaur like me to come 14:14 across one of these things is sort of the find of a lifetime they are very 14:20 expensive on YouTube I saw one a bay I saw one that I looked for and by the way 14:28 the the UPS delivery man and I had quite a long discussion several times I said 14:35 do you realize how much these might be worth and he said yeah but I just don't want to pack the thing up so if I could 14:43 just deliver it that's what I would like to do and sure enough he showed up with it and and my 14:50 one of my dreams of a lifetime came true so I said I'd get away from me let's get 14:57 back to the five seventy and a little bit about how you set this up here is 15:03 the rat's nest patch patch cords 15:08 whatever you want to call it that you set up a tube with along the top you see 15:14 are a series of binding posts on the left are two for heater same on the 15:21 right let me move this turn this to get a little better light on that there we 15:28 are then there are crowns for the cathodes and notice these are symmetric 15:34 then there is grid a and grid B there is 15:40 a minus voltage that you can apply to the Tobias that you there is a plus 15:46 voltage and this is the one place where they are so it begins to be asymmetric 15:51 there is a plate connection and there is a minus DC connection so what are all of 16:01 these for well the grids are the step voltage that we talked about earlier the 16:08 the plate is where you read the plate voltage and the plate current the DC 16:14 plus is to allow you to bias the screen grid for example of a pinto tube and the 16:22 DC minus is in case you need to bias a APN on a tube to a particular level as 16:31 well as the - 150 27 K which has a kind 16:38 of special function that I'm not sure if I'll get into all of that 16:43 but on the face of the 570 16:57 on the right you get a little more light 17:05 on this well something like that you see 17:16 on the right here is a voltmeter that you can select and down below is what it 17:25 shows and it allows you to adjust the heater voltage the positive and negative DC voltage as well as the range of the 17:32 meter then below that let me readjust 17:38 this tripod beneath the meter is the 17:45 step generator and you notice that it allows you to either do 120 or 240 steps 17:53 per second and you can adjust with the red knob the number of steps per family 18:00 I'll show you that in a second on the right is the volts per step and the 18:07 start adjust in other words where that step voltage starts normally you want it to start at zero and you notice that 18:14 there is a little zero marking right here where where this is set right now 18:20 beneath that is the CRT display it 18:28 adjusts the vertical and horizontal sensitivity as well as the vertical and 18:34 horizontal position down here moving to 18:41 the left pardon the moving the tripod here you 18:48 see at the very bottom is the adjustment for the minus DC voltage above that or 18:54 the operating voltages you can set the heater voltage for anywhere from about 18:59 1.2 volts up - I think it's 117 volts so 19:04 pretty wide range of heaters and it adjustable so for example you can run a tube at below or above its normal heater 19:12 voltage to see what that does to the characteristics the this is the control 19:21 for setting the positive DC voltage like for example the screen grid it has both 19:27 a step and an adjustable and by the way this is sort of the traditional Tektronix layout they used for decades 19:35 there while this is a specialized oscilloscope the the main the bread and 19:42 butter of Tektronix were their general-purpose oscilloscopes and they 19:48 used this same basic control setup so once you learn how to use one Tek you 19:53 could use another above that is the 19:58 plate sweep generator that you notice allows you to set the peak volts up to 20:04 500 volts and to adjust the size of the series load resistor finally over here 20:12 is the mains odd to now turn on and you 20:18 notice a little bit of a sound from the fan then you can turn on the test 20:25 voltage and and the reason for this switch is so that there is no voltage on 20:32 this test panel until you're ready for it so in other words you don't have to 20:39 move these wires around while there's voltage on the on the test panel so now 20:45 we're going to turn the test on and you may notice up here 20:52 on the meter it now shows a hundred volts is the plus DC voltage I have it 20:57 set to the plus DC position so now let's 21:05 move this tripod up a little bit turn off some of this light 21:18 and turn up the intensity and turn on 21:25 the grid grid a then and what I'm doing 21:32 is I'm flipping this switch down here from the grid a position to the grid B 21:37 position I know you can't see that because of the glare from these pilot lights but here is grid a that's one 21:45 cube here is grid B and you notice there's a setting in between for 0 what 21:52 that is doing is switching between the grid of this tube and the grid of this 22:00 tube or in the case if you wish you can have two grids of the same tube like a 22:06 dual do dual triode where there are two triodes in the same section and it all 22:12 depends on how you have these wires set up so that is basically how the 570 22:20 works and how you operate it I'm I'm not 22:28 going to go through an extensive you know showing a bunch of different tubes and all of that I'm not sure what 22:33 purpose that would serve though I do realize a few people might be interested in seeing their favorite tube on a 105 22:40 70 but instead what I'm going to do is talk a little bit about some small 22:47 changes that I made to this to this 570 22:53 that improved its performance a little bit 23:00 and one thing the of course they needed 23:05 a cleaning and I cleaned out the interior pretty well vacuumed out as 23:12 much of the dust as I could get cleaned the tubes off and did a pretty good cleaning on the switches and other 23:18 things basically the same thing you do anytime you're restoring a vintage piece of equipment other than that it the the 23:27 unit worked right off the bat so but it had a few quirks and fortunately I was 23:36 able to find and remember a few of the little changes and so things that people 23:43 have done over the years and one of them I'll show you on the schematic take 23:52 Tektronix normally did a wonderful job in fact their equipment was over 23:58 engineered but on this 570 they did make one little design error and and so let 24:08 me show you how I fixed that and since then this unit has performed beautifully 24:14 this is the schematic of the step amplifier in other words the the 24:22 amplifier that takes the the step voltage and buffers it amplifies it and 24:32 provides it to the grid a grid B switch that you see here so let me zero in on 24:38 this part of the schematic so this is 24:45 the final power stage of the step amplifier it consists of a 6c l6 pentode 24:55 and you may notice that the plate is driven directly off the minus 400 volt 25:02 unregulated supply and the cathode is driven through this 120 K resistance 300 25:13 volt unweighted so plus 400 on the plate - 300 on the grid on the cathode 25:20 resistor and then this is a cathode follower the so the signal comes out of 25:27 there and is switched by this grid a grid B switch to the grids of the tubes 25:34 well one of the problems that this stage has is the unregulated supply is located 25:44 a long way away from this 60 l6 and because it does draw a very fairly 25:51 high currents it can it can oscillate 25:57 now early on I think the tech engineers thought that the oscillation was due to 26:04 parasitics in the pen in the test panel of the patch panel and so they released 26:10 some resistor jumper wires to try to 26:15 suppress that and that still does sometimes happen with certain particularly high gain high frequency 26:25 tubes tubes fused for example at UHF frequencies back in the day but the real 26:32 problem with this wasn't it was the decoupling of the minus and plus 26:37 unregulated supplies so all that I needed to do was to add a capacitor very 26:46 close to this tube from the minus regulated and I used to point to 2 micro 26:52 farad you could use a bigger or smaller one just be sure that the voltage rating is sufficient between the minus supply 27:01 and ground and the plus supply and ground and that cleans up the the what 27:09 appears to be oscillation on the grid signal which of course also appears on 27:15 the plate once you have changed the circuit to do that this particular unit worked perfectly 27:22 now there were a few other little issues with the 571 I've already mentioned the 27:30 fact that some tubes would oscillate and and that you could help that by 27:37 suppressing the grid let's go back to this picture here the connection between 27:46 this point and the grid could be replaced by a small resistor patch cord 27:54 that would it's basically called grid suppression and the resistor is often 27:59 called with suppression resistor it was a common way of getting rid of parasitic 28:05 oscillation in tube circuits it's still used in transistor circuits today there 28:10 there are times particularly with MOSFETs where you have to insert a small resistor in the gate lead to keep the 28:19 stage from oscillating but except for 28:24 those a couple of small things and a little bit of maintenance and a little bit of recalibration I was able to get 28:32 this 572 work and it was pretty much working when I got it it just needed a 28:38 little perking up don't we always at our age so oh I think what I'm going to do 28:46 oh I did want to mention something that before I before I finish and that is 28:56 that the plugins that it comes with it 29:04 comes with the pair of octal plugins I'm using the nine pin up plugins right now 29:11 for the the tubes that are in there it comes with a pair of seven pins logins 29:16 it of course comes with a series of patch cords and things of that sort but 29:21 one thing it doesn't come with is a way to do the characteristics of octal tubes 29:28 now back in the day the most prominent tubes were octal 29:35 seven pen and nine pen but Philco partly 29:47 just to get around patent restrictions came up up with a tube type that they 29:53 called a lock ttle let me show you one of those here it looks like this notice 30:05 that there's a small indentation there 30:11 in the in the locating pin other than that it basically is an octal tube these 30:17 pins are smaller physically but they're the same eight pm configuration that oh 30:24 but there's no way to test these or to display these characteristics on the 570 30:29 but there is an easy solution to that and that is if you take a I'm gonna get 30:36 one of these over here if you take an octal tube base that you can buy these 30:42 are very readily available today and you 30:47 pair it with a lottle socket now all that is all that's inside this is just a 30:54 wire from that pin to that pin all the way through in other words eight wires 30:59 just going straight through from side to side and then pull through on the other 31:04 side and soldered but what that allows you to do is to test our lock dual tubes 31:10 which sort of completes the collection 31:16 from the day now if you want to test newer tubes you can do so the problem is 31:24 that the most pins that any of these sockets have is 9 p.m. so if you try to 31:31 display a compact Ron for example you're going to run out of pins if you try to 31:37 connect all of the pins of a John because that has 12 or an O var 31:42 that has 12 pins and there's only a total of nine pins available on the 570 31:51 but you can still do it using the same 31:58 technique you just need to be clever about the or Frugal maybe in the way you 32:03 use your connections so that is my 32:15 experience with the Tektronix type 570 32:22 characteristic curve tracer I hope you've enjoyed this and I hope you've 32:30 enjoyed my other videos at any rate I do 32:36 hope that things will go well for you in the future and look forward to getting 32:42 through this Corona thing civilization will endure and and so I know that 32:49 there's they're happy futures ahead at any rate for now I want to say thanks 32:57 for watching
