Author Topic: poorly seig c3  (Read 1118 times)

Offline davidcurtis021

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poorly seig c3
« on: June 06, 2017, 11:19:17 AM »
hi all

hav'nt been around for a while but could really use some help. On Sunday my machine suddenly died in it's sleep. it didn't give any warning symtoms just failed to restart after tea. it appears to be electricly comatose but i can confirm with basic testing that there is power in up to the emergency stop switch the internal fuse is ok and the motor does run when connected to my 18v drill battery.

i also put a multimeter over the transformer and while i got a reading between the two outer terminals on the secondary coil. i get an out of range reading for the centre one. does this mean the transformer is kaput.

is there also anything else simple i should be checking.




Online John Rudd

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Re: poorly seig c3
« Reply #1 on: June 06, 2017, 12:11:05 PM »
From what I can see on the print side of the board, the centre pin isnt connected to anything....
That said, it could be that the transformer is centre tapped...
Need to see what is on the component side of the board....
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #2 on: June 06, 2017, 01:32:24 PM »
hi
thanks for the help there is definately a connection in the centre i, tried to get a photo but my camera wont stay steady enough,



 i also tried to get some other views of the top.







Online John Rudd

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Re: poorly seig c3
« Reply #3 on: June 06, 2017, 02:16:11 PM »
What is the chip at the end of the board next to the 2 pin socket?
I'm guess its a 7805 regulator..

With power applied, is there any voltage at the two pin socket?
I looked at the photo above in your album, looks like the secondary of the transformer isnt centre tapped....the two outer connections go to a 4 diode bridge, then the regulator....
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #4 on: June 06, 2017, 03:12:39 PM »
hi
yes that is the number printed on it when i put the multimeter on the underside of the 2 pin socket i got a reading of 56.7mv in dc i assume that is 5.6volts

Online John Rudd

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Re: poorly seig c3
« Reply #5 on: June 06, 2017, 03:32:17 PM »
Well is it 56 mV or 5.6 Volts? Hmmm....Depends on what range you have set on your meter.....

Ok, looking at the front of the regulator ( where the numbers are...) the connections are; 1,2 &3 left to right.....connect your meter Black lead to the tab, now connect the Red lead to pin1.... What reading do you get? Set the meter to the 20 range DC volts....then transfer the Red lead to pin3, what reading is on the meter?
Apologies if this is all simplistic, but I dont know what electronic knowledge you have....( I'm a retired engineer,with an electrical/electronic background)
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Offline super7

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Re: poorly seig c3
« Reply #6 on: June 06, 2017, 04:11:55 PM »
Is it not strange that you are getting 0 ohms across the secondary coil in the first pic? Is that not indicative of a dead short ?

Offline davidcurtis021

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Re: poorly seig c3
« Reply #7 on: June 06, 2017, 04:13:31 PM »
Hi John

i will go and do as you suggest first thing tommorow the wife wont let me go out and play anymore tonight. please no apologies simplistic is good, in my former life i was a mushroom farmer so my toolkit was more stilson wrench and large hammer. my limited electrical knowledge came from our local electrician who taught me just enough to change a 3 phase motor or to check i was getting power.
i still take a deep breath and count to ten before going anywhere near live power.

incidently the meter range  was set to auto

Offline awemawson

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Re: poorly seig c3
« Reply #8 on: June 06, 2017, 04:15:23 PM »
A transformer winding will usually show very low resistance to DC. Remember that it is an inductor, and that it's impedance at supply frequency limits it's current, not it's resistance at DC. Same with motor windings.

Andrew Mawson
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #9 on: June 06, 2017, 04:22:35 PM »
Is it not strange that you are getting 0 ohms across the secondary coil in the first pic? Is that not indicative of a dead short ?

the reading wasnt exactly zero it fluctuated between zero and 0.003 my understanding is that is normal and a reading that is 0L indicates something amiss

Offline davidcurtis021

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Re: poorly seig c3
« Reply #10 on: June 06, 2017, 04:41:24 PM »
Well is it 56 mV or 5.6 Volts? Hmmm....Depends on what range you have set on your meter.....

Ok, looking at the front of the regulator ( where the numbers are...) the connections are; 1,2 &3 left to right.....connect your meter Black lead to the tab, now connect the Red lead to pin1.... What reading do you get? Set the meter to the 20 range DC volts....then transfer the Red lead to pin3, what reading is on the meter?
Apologies if this is all simplistic, but I dont know what electronic knowledge you have....( I'm a retired engineer,with an electrical/electronic background)

John when you say connect the black lead to the tab do you mean the silver part on top of the regulator. (just a double check before i do anything to make matters worse)

Online John Rudd

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Re: poorly seig c3
« Reply #11 on: June 06, 2017, 04:45:57 PM »
Is it not strange that you are getting 0 ohms across the secondary coil in the first pic? Is that not indicative of a dead short ?
Super7, with the meter set to uts lowest range in Ohms, the transformer's dc resistance is so low, that it will practically read almost 0 ohms...( the secondary winding that is, because it has so few turns)
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Offline hermetic

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Re: poorly seig c3
« Reply #12 on: June 06, 2017, 04:51:15 PM »
You may be over thinking this! You say you have power to the stop switch, is there power coming out the other side of the stop switch? Did you use this stop switch to stop the machine? If so, check it is not stuck in the off position. Some of them lock off, and have to be reset to work again. Very unusual for something to fail with no power on, and also fail to even give a twitch when turned back on.
Hope this helps
Phil

Online John Rudd

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Re: poorly seig c3
« Reply #13 on: June 06, 2017, 05:04:46 PM »
Have you got power to the speed control board? ( back to what hermetic was saying.... :thumbup:)
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #14 on: June 06, 2017, 05:22:23 PM »
thanks Hermetic  and john
yes i do have power out of the stop switch  my metholody so far has been to follow the power from the mains, into and out of the emergency stop switch down to the control board and into the transformer then at the transformer output is where i began to suspect i may have found a problem, but as said above i'm at level 0 when talking elecrtricals all i'm really capable of is following instructions and reporting back.

Online John Rudd

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Re: poorly seig c3
« Reply #15 on: June 06, 2017, 05:27:17 PM »
Ok, so we know your level, we can guide you if you provide the info .... :zap:
Just dont go hurting yourself....240v isnt nice... :lol:
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #16 on: June 07, 2017, 05:09:14 AM »
Ok, so we know your level, we can guide you if you provide the info .... :zap:
Just dont go hurting yourself....240v isnt nice... :lol:

i thought it might help if i provided a diagram showing what i did yesterday as i don't have the proper terminology in my vocablary. possibly make it easier to understand and see where i have made blunders




that is not the number on my control board but the layout is the same in preview the picture looks too small to read apologies for that but i dont know how to make it larger.

john i have also taken the readings you suggested which from the left pin 008.9 centre pin 0 right pin 000.1 regarding the range button pressing it moved the decimal place to the right.

thank you for the patience which you have shown thus far

Online John Rudd

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Re: poorly seig c3
« Reply #17 on: June 07, 2017, 05:22:06 AM »
So, do you have 5volts dc measured at the connector on the little power supply?

Can you post up a photo of your speed control board please?

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Offline davidcurtis021

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Re: poorly seig c3
« Reply #18 on: June 07, 2017, 07:22:43 AM »
So, do you have 5volts dc measured at the connector on the little power supply?

Can you post up a photo of your speed control board please?
i dont know about the voltage at the 5v connector when i went to measure i was getting inttermitent readings after which i discovered that the inline fuseholder had broken at the end so i had to suspend work till a new one arrives from arc eurotrade which will hopefully arrive tommorow

did take a picture of the control board though which is below.


Online John Rudd

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Re: poorly seig c3
« Reply #19 on: June 07, 2017, 08:55:59 AM »
So, are you now thinking that the broken fuse holder is the reason why your machine isnt operational?
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #20 on: June 07, 2017, 11:06:03 AM »
So, are you now thinking that the broken fuse holder is the reason why your machine isnt operational?

i' can only wish but as i had a good reading at both ends yesterday morning when i started taking it apart i suspect i have managed to break it somehow and the broken fuseholder is just an aditional problem. however when i get a new fuseholder in place it might be prudent to start investigating from the beggining again.

Online John Rudd

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Re: poorly seig c3
« Reply #21 on: June 07, 2017, 11:45:47 AM »
Here's a better wiring diagram....


  http://littlemachineshop.com/reference/drawings/4507-XMT-C3Lathe.pdf

It shows the chuck guard interlock, if yours has one...
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #22 on: June 07, 2017, 01:38:58 PM »
Here's a better wiring diagram....


  http://littlemachineshop.com/reference/drawings/4507-XMT-C3Lathe.pdf

It shows the chuck guard interlock, if yours has one...

thanks for that John. it proved very useful as it reminded me that one thing i had'nt checked so far was the microswitch on the chuck guard i dont know whether it is NO or NC but in any case a continuity test showed out of range for both ways so i know that is duff and am more hopeful that it was the root cause of my problem. when my fuseholder comes hopefully tommorow i will put a link across k3 and k4 and pray for success. Do you think that could have been the problem.


Online John Rudd

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Re: poorly seig c3
« Reply #23 on: June 07, 2017, 02:13:30 PM »
Its very difficult to determine root cause of a problem without having 'hands on' during the investigation....
One can only speculate...
I'll wait until you resolve the fuse holder issue....
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #24 on: June 08, 2017, 08:37:04 AM »
Postman came and went without leaving me with a new fuseholder so took matters into my own hands and constructed a temporary holder from plastic tube



as anticipated other than give stable readings for the multimeter no improvement so next was to bridge the teminals that connected the chuckguard micro switch K3 and K4 on the drawing



On recconeting to the mains and releasing the emergency stop i now have power through the system and a small turn on the speed control brought the motor into life.



just like to say thank you to all who made suggestions and especially John for his guidance.

the upside is now i dont have to spend on  new electrics other than a microswitch i can lavish some cash on giving the machine a complete overhaul starting with the headstock and possible bearing change. followed by getting rid of the horrible digital readouts.