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  1. #41
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    Quote Originally Posted by thanvg View Post
    So, latest report, not much in terms of progress, hope someone can help:

    I went on and rebuilt the diode board, replaced everything apart from the 220Ohm/10kOhm resistors (didn't find them in that store).

    Anyhow, I installed the diode board, started the system, still the same: transformer buzz and smoke from the variac and fuse blown after around 50% of the dial travel. (note that it's not the fuse that's in series with C/CA that gets burnt, it's the other one that feeds the 230ACV to the power feed driver.

    Indicatively:
    - dial at around 25%, variac output 45VAC. With the left-right switch in the off position, all is well. If I turn the switch to left or right, I am getting around 38VDC to the armature (A1-A2), variac starts buzzing a bit and gets HOT. The problem is that if I connect an Ameter in series with the armature, I am only getting 80 mA!

    - Then replaced the Variac with another one I have. At around 30-40% I am getting around 60 VDC on th armature. The variac again got very hot, I mean very hot to the touch and my hands are very tolerant to the heat...Strange thing is that the motor again only drew around 90 mA....

    - Next, hunting ghosts, I thought I'd dish the diode board (w.r.t. the armature). I connected the output of the variac to a diode bridge I had lying around. Again, same things more or less: 45 VDC at the output of the diode bridge, 90 mA into the armature, but the Variac getting smoking hot. It's the part from the 0% up to the slider that gets hot, rest of the coil is ok.

    Adding to all this the observation from last week: motor (both armature and field) fed by a totally different variac through a diode bridge went full speed at more that 230 V drawing only 300 mA!

    I guess the current that the motor draws is indicative of its health, and this one seems ok. Apparently it's the variac to blame (since it's also the fuse at the input of the variac that gets blown). What troubles me though is that without load (armature) the variac behaves, and that, my second one shows the same issues as well....But, it's not impossible that both lathes had blown variacs....


    Any ideas? On what's going or or what I should check next?

    Thanks for listening...

    BR,
    Thanos
    Keep the motor - it ran fine off the other guy's rig.

    BIN, repeat BIN the Mike Foxtrotting Variac AND the Mike Foxtrotting Diode board.

    At my old rates of pay, the silly sumbich has cost you about three thousand Euro already.

    Your life is easily as valuable as that of any other human. We get pretty much the same "TIME" rations at birth.

    That settled? Now go find a Variac & rectifier rig like that other guy had.
    You know all you need to know about your one. It's f**ked up.

    Or skip the Variac and use a small packaged solid-state DC Drive. A 'real' one, (KB, Minarik, Dart, Danfoss-Graham, Eurotherm/Parker-SSD, Sabre...etc..).... not a b***dy lamp-dimmer or "router speed control"..

    What was it that German General said when he finally surrendered Aachen?

    "When the Amerikans started using cannon as sniper rifles, it was time to quit!"

    This bugger is eating too much of your life. And ours.

  2. Likes Billtodd liked this post
  3. #42
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    Quote Originally Posted by thermite View Post
    ...
    That settled? Now go find a Variac & rectifier rig like that other guy had.
    You know all you need to know about your one. It's f**ked up.

    ...

    This bugger is eating too much of your life. And ours.
    Hey there Bill,

    it seems I will have to fire you, you're getting too expensive for me

    Indeed, it's the Variac that seems to be not in order, that's why I got a second one (off another Hardinge), but that could be shot as well, I haven't seen it working.

    Allow me to dig into this a bit more. Usually I don't start replacing stuff if I am not positively sure they are to blame. And, in this particular case, the fact that Variac behaves without the motor on (but diode board connected) is strange.

    I think I'll switch to the bench and get it working there.

    BR,
    Thanos

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    Quote Originally Posted by Billtodd View Post
    So,

    Variac no load is ok ? Where are you measuring volts? At variac? Or motor lead? Switch on or off?

    check you haven't got a shorted loop around variac , i.e no wires that wrap around the torus. No bolts or or mounting hardware that could loop via chassis.

    Have you got a spare goat? (Useful sacrifice when fixing stubborn problem or replacing belts)

    Bill
    Hi there Bill,

    - Variac with no load is ok. Field connected, Variac connected, diode board connected, only armature disconnected. No heat, no noise, nothing. So, this could mean that I haven't screwed up the diode board and also could mean that the Varial is ok.

    - AC voltage measured at the output of the Variac (between 'neutral' and slider.
    - DC voltage is measured at the armature connectors
    - If all is connected and switch is OFF, then no problem. As soon as the motor gets power (switch to left or right) then start the smokes from the varial.

    - No, Variac is physically free, I don't have it installed so I can be sure. Resting on a wooden block...

    - "Have you got a spare goat? (Useful sacrifice when fixing stubborn problem or replacing belts)" didn't get this, sorry.....is 'goat' some kind of tool?

    Many thanks,
    BR,
    Thanos

  5. #44
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    so, motor and variac ok on their own but problems when connected.

    diodes replaced and there is definitely no ac getting to the motor (shorted diode or misplaced wire)

    Ok let us try logic.

    What you are seeing is a loud hum and lots of heat at relatively low voltages , so that suggests low resistance or impedance and some serious current

    so ,something is shorting the output of the Variac . if that current isn't going into the motor , it has to be going somewhere else (Kirchhoff's circuit law) .

    Check:

    Shorts to ground/chassis in motor or tag board at the back of the control box and any where inbetween.

    Misplaced, swapped wires connecting common points

    Obscure bastards, where some other bastard has replaced a short screw with a longer one , so when it is disconnected and loose , all works ok , screw it up tight and boom (BTDT) .

    "No problem can resist the power of sustained thinking" - Aristotle (another old Greek guy ;-))

    Goat (n): animal, leg in each corner , useful for blood sacrifice and curries. Handy alternative when you've already promised your first-born to Satan in order to get the car to start that morning

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    Quote Originally Posted by Billtodd View Post
    ...

    What you are seeing is a loud hum and lots of heat at relatively low voltages , so that suggests low resistance or impedance and some serious current

    so ,something is shorting the output of the Variac . if that current isn't going into the motor , it has to be going somewhere else (Kirchhoff's circuit law) .

    Check:

    Shorts to ground/chassis in motor or tag board at the back of the control box and any where inbetween.

    Misplaced, swapped wires connecting common points

    Obscure bastards, where some other bastard has replaced a short screw with a longer one , so when it is disconnected and loose , all works ok , screw it up tight and boom (BTDT) .

    "No problem can resist the power of sustained thinking" - Aristotle (another old Greek guy ;-))

    Goat (n): animal, leg in each corner , useful for blood sacrifice and curries. Handy alternative when you've already promised your first-born to Satan in order to get the car to start that morning



    Haha, still laughing.... no...no goat at hand, let's stick to sustained thinking!

    Right about current going somewhere, let's narrow it down.

    90 mA that I measured going into the armature are not what goes through the Variac and starts toasting it, there is something higher there.
    These 90 mA are also what I am getting when I replace the diode board with a diode bridge. So it's not something shorting at the diode board.
    No heat and weird stuff when the Variac output is not connected, so it's not that the variac has a short internally (or the damned long screws).

    I am thinking that I might be doing something wrong, but that's the simplest circuit in the world (not that I can't mess something there, I can). What troubles me is that both Variacs that I have, demonstrate the same exact behavior. Right, they can both be faulty, let's assume this. But what are the chances that they are faulty in the exact same way? They would start silly things at different positions of the slider, I would expect, if they were both toasted.

    I think, next step is to move everything to the bench. I'll try to track the currents and see what goes where.

    I'll report back.

    Many thanks,
    Thanos

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    Is that 90mA AC or DC?, is it on both wires going to armature ?

    (If you've got AC going to the armature or field ,and DC to the other, it would likely make more noise than a goat mid-sacrifice but it still is worth checking).

    If you get a smoothly increasing voltage from the variacs unloaded* , they are likely to be OK.



    *if in doubt, load output with an incandescent/tungsten filament 20-40w/120-240v bulb. Bulbs are almost as useful as goats for fixing electrical problems and often better than digital multimeters (DMMs can easily mislead) .

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    Quote Originally Posted by Billtodd View Post
    Is that 90mA AC or DC?, is it on both wires going to armature ?

    (If you've got AC going to the armature or field ,and DC to the other, it would likely make more noise than a goat mid-sacrifice but it still is worth checking).

    If you get a smoothly increasing voltage from the variacs unloaded* , they are likely to be OK.



    *if in doubt, load output with an incandescent/tungsten filament 20-40w/120-240v bulb. Bulbs are almost as useful as goats for fixing electrical problems and often better than digital multimeters (DMMs can easily mislead) .
    It's 90mA DC going to the armature. Didn't check for AC, will do. Also, checked one wire only. Are you thinking about a leakage in the motor when suggesting measuring current at both wires?

    Yes, Variacs unloaded output a smoothly increasing voltage measured with a DMM. I did put right now in my backpack a 40W 230V lamp I had lying around here at work to verify as you suggested. I had bought it exactly for this reason, to check if an SSR driven by a PWM signal actually worked on a machine I repaired here... It's my own stuff I can't seem to be able to fix

    Many thanks
    Thanos

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    Are you thinking about a leakage in the motor when suggesting measuring current at both wires?
    Yes, just trying to eliminate internal short that might not have shown up with your external power test.

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    Quote Originally Posted by thanvg View Post
    - "Have you got a spare goat? (Useful sacrifice when fixing stubborn problem or replacing belts)" didn't get this, sorry.....is 'goat' some kind of tool?

    Many thanks,
    BR,
    Thanos
    Thanos. You are in GREECE!

    A decorative bas relief at a theatre, or a player on the stage adorned with the mask of the head of a goat sound familiar?

    According to Aristotle, tragedy evolved from the satyr dithyramb, an Ancient Greek hymn, which was sung along with dancing in honor of Dionysus. The term τραγῳδία, derived from τράγος "goat" and ᾠδή "song", means "song of the goats," referring to the chorus of satyrs. Others suggest that the term came into being when the legendary Thespis (the root for the English word thespian) competed in the first tragic competition for the prize of a goat (hence tragedy).[1]
    Comical exercise, this power source, were it not tragic?

    There isn't a great deal of USE in testing a Variac unloaded.

    Try at least low-inductive. mostly resistive loads with an incandescent lamp socket and progressively larger lamp Wattages.

    They are happy enough on DC, so that supports load testing the diode board as well.

    Nobody has to die if you burn out a lamp, either.

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    Quote Originally Posted by thermite View Post
    Thanos. You are in GREECE!

    A decorative bas relief at a theatre, or a player on the stage adorned with the mask of the head of a goat sound familiar?
    Yes, yes...what can I say... Always not 100% certain about my English, especially tool slang, so I thought... haha...

    Quote Originally Posted by thermite View Post

    Comical exercise, this power source, were it not tragic?

    There isn't a great deal of USE in testing a Variac unloaded.

    Try at least low-inductive. mostly resistive loads with an incandescent lamp socket and progressively larger lamp Wattages.

    They are happy enough on DC, so that supports load testing the diode board as well.

    Nobody has to die if you burn out a lamp, either.
    Yeap, as I said, got my incandescent lamp already at hand for my debug session later today. And, right, nobody has to die if a lamp gets burnt, but, it won't be that easy to replace! This type is getting scarce lately!

    Many thanks
    Thanos

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    Quote Originally Posted by thanvg View Post
    Yes, yes...what can I say... Always not 100% certain about my English, especially tool slang, so I thought... haha...



    Yeap, as I said, got my incandescent lamp already at hand for my debug session later today. And, right, nobody has to die if a lamp gets burnt, but, it won't be that easy to replace! This type is getting scarce lately!

    Many thanks
    Thanos
    Well testing your English.. you could try a small Russell Hobbs.



    (To tea kettles in blighty as Coke is to soft drinks or Xerox to serology.)

    Seriously. "Travel" size kettle/hot-pot about right?

    Bigger motors and DC Drives, here. Replacement stove "burner" coils in far larger wattages are under ten bucks. My largest is a 9 KW "canning" element.

    And what is it we know about electric cooker elements?

    They can stand the heat!

    Even if they DID "get out of the kitchen" already!


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    Hi there guys,

    I have some progress to report, though there are still some 'grey' points...

    Here is what I set up yesterday:



    All on the bench, easy to measure and verify.

    Started nice and slow.
    - first hooked the lamp at the Varial output, nice and smooth (details available but not important)
    - then connected the lamp at the diode board output for the armature (A1, A2), again everything was nice and smooth.

    I was checking voltages and, also, had an Ameter at the input of the system permanently connected.

    And then, I replaced the lamp with the armature connection. What I got ranged from 2 A at the input, to the mains protective relay shutting down everything. Apparently there was a serious short somewhere.

    So, I checked the armature-to-earth resistance and found that one cable was at 40 Ohm and the other one at 1 Ohm!!!
    Took the motor apart and checked the rotor. No shorts there. Next, focused on the brushes:



    Took them apart and found one of the two brush insulators like this:



    This thing cages the brass brush holder and I guess it's not supposed to be like this

    So, I turned one out of acetal, put everything back together and measured. No resistance between any of the armature connections and the earth!

    Quickly reconnected everything and started the motor and everything seemed to be in order. Left it running at full setting of the Variac for more than 5 mins. System drew 300 mA AC at the input. Armature was drawing 115 mA DC running at 270V! Everything was super smooth and the Variac was ice cold!!!!!!!

    I guess we nailed it, but I won't hurry to praise the day before it's over, I still have to test it on the machine...

    However there are two things I don't like:

    - I had measured the motor before, it was ok. And I had it running at the other guy, worked perfectly without excessive current consumption. I guess something moved....But still, even with that insulating sleeve so worn, I can't say where the short was exactly...

    - most importantly, I can't say why the automatic relay of the mains didn't kick in when I was testing on the machine. I'll recheck my grounds, I can't find any other explanation. It's not a nice thing to have such a leakage towards a part of your machine and the protection not kicking in...

    Closing, I guess Bill (you know which Bill you are) that if, the day before yesterday, I had measured current at both the armature cables I would have seen all that current due to the short. 50% chance and I picked the 'wrong' cable

    Will report back after I install it on the machine.

    Thanks again.

    BR,
    Thanos

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    Great News :-)

    Well done - 'persistent fiddling' wins again .

    There is every chance that , since in the HLV-H I have and probably any UK made K1 will have one side, the neutral, of the 240vac transformer supply connected to the chassis of the lathe , when you tested the motor with a separate supply that neutral side was connected to the shorted terminal. (or , because no goats were available, the short chose that moment to be long ;-))

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    Quote Originally Posted by Billtodd View Post
    Great News :-)

    Well done - 'persistent fiddling' wins again .

    There is every chance that , since in the HLV-H I have and probably any UK made K1 will have one side, the neutral, of the 240vac transformer supply connected to the chassis of the lathe , when you tested the motor with a separate supply that neutral side was connected to the shorted terminal. (or , because no goats were available, the short chose that moment to be long ;-))
    Well, something like that....

    I will have to check. I think the chassis is grounded with a separate wire to the mains, or, at least, that's what I hope is the case.

    Let's see how this all will workout tonight that I'll put it all on the machine....

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    Quote Originally Posted by thanvg View Post
    Hi there guys,

    I have some progress to report, though there are still some 'grey' points...

    Here is what I set up yesterday:



    All on the bench, easy to measure and verify.

    Started nice and slow.
    - first hooked the lamp at the Varial output, nice and smooth (details available but not important)
    - then connected the lamp at the diode board output for the armature (A1, A2), again everything was nice and smooth.

    I was checking voltages and, also, had an Ameter at the input of the system permanently connected.

    And then, I replaced the lamp with the armature connection. What I got ranged from 2 A at the input, to the mains protective relay shutting down everything. Apparently there was a serious short somewhere.

    So, I checked the armature-to-earth resistance and found that one cable was at 40 Ohm and the other one at 1 Ohm!!!
    Took the motor apart and checked the rotor. No shorts there. Next, focused on the brushes:



    Took them apart and found one of the two brush insulators like this:



    This thing cages the brass brush holder and I guess it's not supposed to be like this

    So, I turned one out of acetal, put everything back together and measured. No resistance between any of the armature connections and the earth!

    Quickly reconnected everything and started the motor and everything seemed to be in order. Left it running at full setting of the Variac for more than 5 mins. System drew 300 mA AC at the input. Armature was drawing 115 mA DC running at 270V! Everything was super smooth and the Variac was ice cold!!!!!!!

    I guess we nailed it, but I won't hurry to praise the day before it's over, I still have to test it on the machine...

    However there are two things I don't like:

    - I had measured the motor before, it was ok. And I had it running at the other guy, worked perfectly without excessive current consumption. I guess something moved....But still, even with that insulating sleeve so worn, I can't say where the short was exactly...

    - most importantly, I can't say why the automatic relay of the mains didn't kick in when I was testing on the machine. I'll recheck my grounds, I can't find any other explanation. It's not a nice thing to have such a leakage towards a part of your machine and the protection not kicking in...

    Closing, I guess Bill (you know which Bill you are) that if, the day before yesterday, I had measured current at both the armature cables I would have seen all that current due to the short. 50% chance and I picked the 'wrong' cable

    Will report back after I install it on the machine.

    Thanks again.

    BR,
    Thanos
    I was wrong. I am HAPPY that I was wrong! Good on yah for persistence!

    You'd have to know Greeks..



    "Turned ONE out of Acetal."?

    Good idea to make another one, replace BOTH, then?

    This wants research - as an old linen-bakelite fossil, here - I do not know its characteristics in this regard.

    But I'm not sure Acetal is up for long-term heat build-up? Softening and age effects could lead to a similar fault or shifting of the holder?

    W/R reliance on "mains" protective devices: My test bench has its own fuse and breaker routing capability. I can route a feed via anything from 60 A 3-Phase all the way down to 9AG "instrument" fuses of the sort meant to protect a meter.

    As a cheap minimum, put an Edison-base socket in a single-phase line. Not one can use Old Skewl screw-in plug fuses or their "Mini-breaker" screw-ins OR place an incandescent lamp in series as a current-limiter.

    Same again the cartridge fuse holders and that whole family of goods.

    Coupla terminal blocks, pin jacks for meters, some wires in each of several colours, and the whole rig take up very little space, can easily be stored.

    Might have to order the goods online, but it can be worth it.

    I also have a whole tribe of transformers set up to be connected for all sorts of voltages, one of them a 2 KVA multi-tap with rotary selector, and a 5 KVA Variac with built-in meters.

    Those DO take up some space, but - so far, at least - the bench hasn't blown away in a breeze!


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    Quote Originally Posted by thermite View Post
    ...

    Good idea to make another one, replace BOTH, then?

    ...

    W/R reliance on "mains" protective devices: My test bench has its own fuse and breaker routing capability. I can route a feed via anything from 60 A 3-Phase all the way down to 9AG "instrument" fuses of the sort meant to protect a meter.

    ...

    Hey there Bill,

    yea, glad it did work out!
    Tonight I checked again after hooking everything up on the actual machine. Everything works perfectly! And, as one would expect....second variac works just as nicely, which is great news! (both these variacs took some heating during my experiments lately, I hope they don't collapse after a while...)

    Sadly I cannot put it to actual test, by really power feed somethng, since my carriage at the moment doesn't have a single gear in. This is where decades of trying to lubricate everything with cutting fluid instead of oil lead. Thank you previous owners....

    Thanks for the advice regarding electrical testing, that's what I would like to have if I was setup for more electrical work (and had the space of course). Makes your life easier and saves so much time....
    (I did opt for a resetable fuse in line with the mains though, thought that far... )

    BR,
    thanos

    ps. first thing I'll make on the machine after remaking some gears and putting it back together will be these bakelite linens and the screw-in caps for the brushes, one is missing and the other is falling apart.

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    Quote Originally Posted by thanvg View Post
    these bakelite linens and the screw-in caps for the brushes, one is missing and the other is falling apart.
    You "might" be OK with G10 Fibreglass Reinforced Plastic or Micarta/Formica, Kraft paper Phenolic, either of which may be easier to find as rod stock drops than Old Skewl linen-bakelite.

    Others here on PM will know far more about that "modern" stuff.

    I haven't quite run-out of Linen-Bakelite yet!


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    Quote Originally Posted by thermite View Post
    You "might" be OK with G10 Fibreglass Reinforced Plastic or Micarta/Formica, Kraft paper Phenolic, either of which may be easier to find as rod stock drops than Old Skewl linen-bakelite.

    Others here on PM will know far more about that "modern" stuff.

    I haven't quite run-out of Linen-Bakelite yet!

    Right Bill, I guess phenolic would work just fine. I did have a piece lying around but it was much larger in diameter and I didn't feel like wasting it. So, I guess it will just keep on sitting in that drawer forever...


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