1000V insulation tester (Ganz XS)

so today let's explore this ulation tester it was donated by a viewer so big thanks for the donation it comes in a nice leather case and let's remove it from it if I can because it's sort of falling apart this is old probably from the 80s or maybe even 7s and the point of it is to test insulations to measure their resistance and it seems that the one can use for the test from 100 Vol all the way to 1,000 Vols selected using this switch and it has three ranges one is in kilohms and the other two are in megaohms there is an analog meter with three scales kiloohms Mega ohms and another Mega ohm scale and here is the on button which doesn't stay in but I guess it's not a failure it's meant to be like this to prevent you from forgetting it on and discharging the batteries and also to prevent you from getting a shock from the terminals and if you get a shock you jump off the button and it turns off here is some calibration zeroing potentiometer and it has three terminals here one seems to be common for the ranges and I guess this one is for the kiloohms and this one for the Mega ohms depending on which range you select here and this thing doesn't seem to be in the best condition but of course I'm not complaining about something donated but it seems to be dropped and this is not from the shipping and there was no big chunk of plastic in the box so this was already broken before the shipping and of course maybe the shipping made it even worse it was actually held together using a lot of screws but all of them are actually broken now but the worst thing is I guess this analog meter seems to be stuck when I turn it around its excess the needle should be moving but it's not moving it's stuck here and this also doesn't seem to be from the shipping because he sent me a picture of it and it was already about in this position in the picture of course normally the needle of the analog meter with no current in its coil should be here even though maybe the meter is backward and the zero should be here because basically the less resistance the more current it passes so maybe the needle actually goes to the left with more current it would also make sense because typically a potential meter calibrates the meter at the maximum point and this physical knob calibrates it to the zero current point I don't even have to remove any screws to see what's inside of it there are various switches in it for all the renes and they interlocking using this metal bar and this one is cut out here so it's actually intentional that this one does not stay in and here's the potentiometer for the calibration seems like a double potential meter with some resistor on it and of course here are the batteries and it doesn't seem to have any type number other than XS good luck trying to Google the schematic of it well if you try to Google XS it will probably show some cloths in a size that's probably illegal now because it would cause Burger eaters some psychological damage so instead of Googling it we have to figure it out somehow I don't see any point trying to turn it on before disassembling it because of this broken meter the needle is stuck and if I turn this it actually moves but it doesn't move like this it should so let's check the batteries and then open it here's the battery SP let's unscrew the screws from it and see the batteries hopefully not completely rotten and leaking everywhere which is quite typical for old devices and it says battery R20 7 time 1.5 volts 1.5 amps maximum current it seems to be a little bit rotten here and it seems like diesels in it 1.5 volts made in Hungary some makeer probably something in Hungarian I also don't understand this 6.30 ft plus and it seems to be dated 1981 the fifth day of some month which I don't understand in Hungarian of course and is it the production or the expiration but in either case it's bloody old it's not even leaking much surprisingly very old school batter is I would expect the batteries over 40 years old to be more rotten than this actually this is nice surprise some small spots on it all of them seems to have the same date on them it's dirty here but it doesn't seem to be a liquid it's good of course this foam is completely rot and falling apart surprisingly the contacts seem to be quite clean not rusted or corroded nice no contact corrosion from leakage in more than 40 years compared to something like durel I guess there are some screws going from this side but I don't really see any pint on screwing them is something under this it's not a screw under it it's just a hole I'm trying to turn this screw which has nowhere to go a poor homeless screw well let just open it like this you can see the switches at the bottom here and there is a Transformer I guess there is some inverter two power transistors with this Transformer probably make some inverter and it's an iron core not ferite so I guess the inverter runs at quite a low frequency maybe just a couple hundred Herz definitely not many Kilz some 1 kilov volt 150 Nano capacitors probably smoothing the voltage from the inverter which goes up to 1,000 volts I guess there is not really that much to it it's an inverter with two transistors producing from 100 to 1,000 volts and a couple transistors and then it's mostly just some resistors and calibration potentiometers and the principle isn't really that complex but it looks more complex because it has more ranges four voltage ranges and three resistance ranges but at time it's probably using just some of these potentiometers and resistors definitely not all I gu three potential meters here calibrating the three resistance ranges and four potential meters here adjusting the four voltage range is here can I completely open it somehow and of course this analog meter is completely disintegrated of course the broken plastic bits could be glued back or you could stick some piece of new plastic Over the Hole or you have a lot of sticky tape if you're desperate but not sure it's going to be repairable with this smashed meter this thing probably completely comes off and here's the magnet which is also loosen it there is some coil with a wire going to it not sure where's the other and the blue one is probably going to the other side of it am I supposed to completely open it am I supposed to unscrew the switches from the front panel here because the wires are quite short and going from here to somewhere here you have to get the meter out to see if it's repairable because if the meter is not then the entire machine is not worth any repair course of course this is also held in place using some wedges or whatever that is it pops out of course this is very easy to break if it's not broken already it's not two wires and it's rubbing let's document where the wires go and let's cut it out before I damage it and let's explore the rest of it and then let's try to fix the meter there are these stands I guess when it was assembled this board was actually part of this side and then the back on this but because it was broken I opened it in the wrong order here are the connections between the batteries it seems like three connections so the battery had some top on it it seems like the red one is the positive of all batteries the blue one is the negative and the black one is like one battery below the main positive One battery voltage lower than this one for some perpose and the total voltage of the batteries was 10.5 Vols but split into nine and 1.5 on top of it and the board has just connections here no components and here there is a lot of components here's I guess the inverter some diode for rectification high voltage resistor power transistors but no heat syn it's probably not a very powerful inverter just for the sake of measuring something some small transistors three small ones I guess if you're measuring like 5,000 Mega the current is so low through this resistance that you have to amplify the current before it goes into the meter there's a special double potential meter which says 5.6 KMS plus 10 kilms so it's two potentiometers and each of them is different and it's dated 1978 and both of them are 1 watt plusus 20% Nice and here are the switches which I probably didn't have to remove but anyway and here's the meter and the last division on the highest scale is 5,000 Mega quite a high resistance it actually changes based on what range you select for 500 volts I guess you reading it directly but for other voltages you're reading it with some multiplication Factor so when you for example Select 1 kilov volt you're multiplying it by two so if it says 5,000 Mega it's actually 10,000 Mega can we somehow fix it it's a big magnet with a rotating coil in it I gu some dampening mechanism so it doesn't oscillate too much here's the calibration which basically moves the entire thing it actually moves when I move the calibration lever but it doesn't move freely on its own it's rubbing it seems to be a different mechanism than I expected there is no hairspring and no needle bearing it seems like there is a string going through the center and this string not a spring actually works as a connection but also as the return spring the string goes from this springy piece of metal which is also the electrode the negative it goes into the coil and also gives it basically a support it's probably it's bearing and on the other side it looks like it's bearing ly visible it's very thin and this string is actually broken the string coming from this springy metal which was the positive terminal and I guess it was going into the center of this hole supporting the shaft and this doesn't really seem to be very repairable unfortunately it was probably stretched and holding it centered in the magnet but now it's of course off center and ring and also have no electrical connection and also no return Force this is not going to work measuring the resistance between the wires and it shows open circuit you going to see the string still intact on this side but here it's broken I don't think I can fix this you can try to disassemble it and see I'm trying to take this one off and some piece of plastic is falling over here this is whole plus there was this thing on it and this springy washer on it and this plastic is disintegrating now this is the string holder and the contact basically and through it the string went into the hole in the center of the moving coil mechanism and because the meter is broken I was looking some other meters I have maybe I can stick some other into it even though of course the scale is not going to match but at least let's try to see if it moves or something and of course each of them has a different sensitivity this one is I guess 1 milliamp very insensitive the best ones are I guess about 50 microamps these are 200 microamps and this one even has a warranty 970 nice but unfortunately I was measuring these three and they're all open circuit for some reason so let's try this meter this one is 400 microamps not the most sensitive but it's big and we can just see if it does something I'm wiring it in I'm putting two anti parallel diodes on it to prevent it from being damaged if something goes wrong but in a normal operation the voltage drop never reaches the voltage drop of the diodes and of course it requires a top the battery and I don't have seven diesels so I'm wiring a double bench power supply into it it's six Batteries Plus One and the bench power supply also has the advantage of measuring the current of the two rails and having a current limit if something goes wrong and here's my double bench power supply one output is set to 1.5 volts and the other one to 9 Vols my bench multimeters monitoring the voltages and these meters are going to show the current draw I'm going to press D on a button almost nothing is happening I guess in the kilo range it draws almost no current let's switch it to one of the mega oh ranges now it draws more current about 150 or 200 milliamps and I can here the inverter pressing the on button in one of the mega ohm ranges does not move the needle here take gu when no resistance is connected it actually is meant to show nothing the needle is not meant to move so let's try to short it with a wire and let's see now what happens when I press it and it also draws more current when it's shorter and these meters are 1 o full scale so it's now drawing about 400 milliamps and the meter is not moving of course I had it at 250 volts and the current draw depends on the setting of the voltage the higher the voltage the more the inverter draws 100 volt 250 volts 500 volt 1,000 volts a bit over one arm up now switch The Meters from one to 2 AR range it's about 1.1 amp I guess and also the consumption changes based on the calibration potentiometer position I guess the calibration potentiometer actually changes the voltage of the inverter now it's in the 250 volt position and the potential meter actually changes it from 218 to 368 and the 100 volt position and the potenti meter can actually regulate it from 89 to 150 and this was of course the mega ohm ranges now testing the kiloohm range and it's actually putting 1.5 volt into it this has no effect it's actually putting the one cell voltage into the terminals for the kiloohm range it was basically this voltage and when I short it in the kilom range the meter is actually moving backwards a little bit here let's flip it s the right way not really moving much and of course when the terminals are open circuit it's not moving at all open circuit terminals shorted terminals open shorted not much of a difference is it possible this one was that much more sensitive and I also guess it was backwards really this was with no current and this was with full current basically mirror image of a normal meter I was wondering why it's not doing anything in the mega ohm range so I just randomly poked my meter into this capacitor and bloody hell the capacitor seems to be shorted I disordered the one p to verify it's the capacitor and not something in the board shorted capacitor nice it's 47 narad 250 volt DC so let's try to replace it I have a 47 Nano 1 Kil volt capacitor which seems to be made in 82 seems appropriate measures 48 Nano estimating the dissipation factor using my ring tester it seems to be just a polyester but I don't think it requires a polypropylene capacitor the capacitor's in sets to 250 volts the high mega ohm range the mega ohm terminals shorted and let's see and it's moving nice and the meter is showing nothing when it's open a circuit and some deflection when it's short circuit it's basically the other way than the original scale now the infinity resistance is here and the zero resistance should be here I guess the calibration is done by shorting it and then turning this to get it basically to zero which was the maximum deflection for the meter of course I can't get it to the full deflection because the meter probably is less sensitive than the original and there is a small electrolytic capacitor in it 22 microfarads let's measure the ESR of it and the ESR is 1.9 ohms which is really not that horrible it should still work and that's the only electroic capacitor in it and measuring the waveform on the primary of the power transformer in the inverter and it's about 2.2 khz frequency a nice Square wave and it's changing as I turn the calibration potential [Music] meter and believe it or not I actually found the schematic of it it helped to add the name of the maker into the search and here is the inverter the two power transistors driving the power transformer here is the primary the secondary with stps which are switched a doubler and there is a switched resistance in series with the terminals and also some switched resistances in the feedback regulating the voltage when it reaches the nominal voltage I guess it somehow shifts the frequency of it to limit the power and here's the self oscillating pair of small transistors with a small transformer and this drives the basis of the main power transistors and of course the high voltage from the inverter is used for the Mega ohm ranges and for the kiloohm ranges it's using Just One battery or one cell voltage 1.5 volts and all the transistors are actually part of the inverter there is no transistor in the measuring circuitry and all of the transistors are PNP germanium and the circuit has a common positive which is quite typical for germanium transistor circuits and I was thinking some transistor amplifies the current before it goes into the meter but it's not the case here and with germanium transistors it wouldn't be possible because the base to emter Junction has a lot of leakage current so it can't sense a very low current basically and the principle is very simple either the high voltage or the 10.5 volt voltage goes via the measured resistance and then it goes into the meter with some resistive networks for the kilohm range working at 1.5 volts it goes via this network and for Mega there is some serious resistance then the measured resistance and then it goes again via some other network of resistive dividers basically plus some zener which is is it a protection or is it giving it a more logarithmic scale I don't know and there are two resistors switched for the two Mega oh ranges some calibration potentiometers another calibration potentiometer and the parallel capacitor and this is the capacitor which was shorted and basically the meter was shorted via this capacitor and that's why it was not showing any deflection before I change this capacitor and I guess you're not supposed to switch the ranges while it's running because I guess these switches disconnect one contact before connecting the other one and if you switch it while it's running momentarily there is no resistor connected parallel to the capacitor there is nothing pulling the voltage down and the capacitor might actually charge to the full 1 Kilt and this is I guess how this 250 volt capacitor got shorted or maybe because of a poor contact in the switches when know whichwich is making contact here the capacitor can charge charge to most of the voltage of course the inverter is not running for the kilom range and also the top on the battery is only used for the kilohm range so when using it for the Mega ohms you could basically just use a single power supply and of course the kiloh range is sort of useless for me because it's basically doing what a normal multimeter does with way less accuracy than the multimeter only the mega oh range is actually interesting because it's using various high voltages for the test and the inverter voltage feedback is basically a resistive either with this upper resistance this lower resistance some zener and when the voltage reaches the nominal level it's pulling the supply voltage of this self oscillating base driver down and unfortunately it doesn't say the sensitivity of this meter but I guess it must have been a bloody sensitive meter the most sensitive analog meter I have seen was I guess 50 microamps not sure what was this it has quite a big strong magnet which helped it to be quite sensitive the torque in it is basically the product of the coil magnetic field and the magnet magnetic field so if the magnet is very strong then you need less magnetic field from the coil for the low magga ohm range it's full deflection for zero resistance this is showing just about nothing and for the high mega oh range it's 10 mega ohms full deflection and it's going to shwing very little it shows much more deflection when it's shorted in the high mega oh range but zero resistance is not even on this scale now testing it with the digital meter it's showing about 6 microamps and this would have been the full deflection is it even possible the meter was that sensitive this is the low Mega range shorted and this is the high mega range with 10 megaohms it can actually be also calibrated to about four or five microamps I'm still trying to figure out these resistors and switches here I guess this is for the low Mega arm range and this is for the high mega arm range but it's only conducting above a certain voltage the voltage drop of this zener I measured it it's about 4.5 volts and this low resistance potential meter is used for the Kil range this one is for the low Mega range and in the high mega oh range I guess none of these two is connected which makes more sense for the high mega ohm range it has to be bloody sensitive so it has no parallel resistors on the meter only the 100 kilm one which is a higher resistance but not these which are much lower resistances 2.2 and 10 Kil HS and there before this High Resistance P here when one of these is connected most of the current goes via a low resistance P here or here and very little of it goes via these multiple 100 kiloohm resistors and of course the schematic isn't exactly the same version but at least similar I tested all components in this Mega oh range circuitry and I measured what set on these potentiometers and everything seems to be good here all the components in seem good and they just can't get more than about 6 microamps in this meter and no matter how I calculate from the values in the schematic it always looks like the meter was like 5 or 10 Micro super sensitive and just looking at the high mega oh scale it's 100 megaohms per half deflection basically and the default range without multiplying is 500 Vols and at 500 volts 100 megaohms is going to pass Five microamps which if it was half deflection the full deflection would be 10 microamps and this is if all the current was going through the meter whereas in reality some of it goes through the parallel resistors which means the full deflection of the meter was 10 microamps at most probably less but at half the reflection maybe a little bit of the current is already going through the Zer and about 1 fifth of the deflection is 500 mahs this is 1 microamp 1/ fif of the deflection and at this point the xener is not yet conducting I guess and if 1/ fifth of the deflection is 1 microamp the full deflection has to be 5 micro and the 10 mega oh resistance of this meter should give it full deflection and it's showing about 5.8 micro arms and the low Mega range with the terminals shorted again should show full deflection and is showing 6.1 micro arms all my measurements and calculations are pointing at about five or 6 microamps unfortunately none of my meters is anywhere near this sensitive so I have to just conclude I have absolutely nothing to replace it and I really gu this in make the scale logar make looking at this scale it's half the resistance double the deflection up to about here from here to here the voltage drop of this resistor and this potentiometer is not enough to make this xener conduct but from here on it's logarithmic because of the logarithmic voltamp characteristic of the xener well this turned into a long confusing boring video with quite a disappointing and but that's life we didn't fix it but at least we learned something and of course if if you've made it that far please consider subscribing supporting my channel on patreon or using the thanks button and big thanks to all of you who already support me this channel couldn't exist without you and I wish you a Happy New Year

Channel: DiodeGoneWild

Views: 14,298

Keywords: Ganz, XS, insulation tester, Germanium, 1000V, MΩ, insulation resistance

Id: ik776TOwQ8g

Length: 26min 24sec (1584 seconds)

Published: Fri Jan 05 2024