Blown band saw circuit.

[Marischal EllisParticipant @marischalellis28661]

I jammed my ultimate pride and joy, a De Walt 3501 Band saw of 30 + years. Instantly cut-out with a pop and doesn't work now. I use it so much and is so convenient to me. How stupid of me.

I did a long think through; the trip switch was not working (open or closed?) and bought a new one. I also bought a new neon warning light (white Light) which had never worked. (Possibly a running light). The start capacitor which I commenced the checking with was AOK . Re-assembled switch box but nothing happened. I pressed the trip switch and kept it pressed (open or closed?) to try it and motor started up, so that was OK. The contact switches as a set of four are now no longer available via De Walt and were about £40 + or so, years ago

Having fiddled with things, and my mind, I now think that the contacts are bad (jammed open or shut?) but what do I replace them with, as the capacitor is required and 'modern' motors appear to have built-in capacitors which I think cut-out on functioning?

Current Off/On button switches (load is 16 amps) would seem possible but I don't know how a capacitor would be wired in as they appear to rely on cutting off instantly after firing up, so running as I did would not last too long. More correctly it is probably the magnetic coil that is damaged so no control over instant time.

My question is : What can I ,replace my broken contacts and/or switches with. I can add a elect box housing or what ever is need, to house new 'bits'. I have drawn the circuit as I see it and can see why it presently works by keeping my finger on the trip switch.

Your help and advice would be most welcome as it is not my subject. As I grow older there are lots and more of 'not my subject' but that is another story for another day. A way of switching and a means of including a start capacitor would seem to be the way forward if that is correct.

Diagram of circuit.

[Marischal EllisParticipant @marischalellis28661]

Help asked for please.

[clogsParticipant @clogs]

shame after all those years…..

their machine wiring was always a bit weird…….

there's plenty of contactors out there…..and also many varied size and style of boxes…none of which is expensive….

I can't help u with the wiring but I'd be inclined to bin the lot and go with the Brit idea….no volt stop start switch etc….

even if it ment replacing the motor…..but that should not be nec……

and I'm sure somebody who's a wizz with wiring will be along shortly…..

My Bridgeport's wiring was a messy affair, will just bin the lot and replace all contactors……

not so cheap but it'll last my lifetime…and it will be reliable…

[Les Jones 1Participant @lesjones1]

It sounds like either the coil on the coil on the contactor is open circuit or the maintainer contact is not holding the coil in after the start button has been pressed. The stop button will be a normally close push button and if that was open circuit it would also prevent the the coil from holding the contactor in. I assume the rectangular thing with 8 connections is the combined contactor and start and stop buttons. you have not shown which connections go to the coil or the layout of the contact sets. I have tried to find a picture of your contactor assembly but failed. Some pictures of the contactor may help in understanding the contact and coil connections. I think a standard NVR switch can be made to work.

Les.

[Ed DuffnerParticipant @edduffner79357]

What is the large rectangular block between the capacitor and the Warning Light" ? Is it a connector or 4-pole switch?

Ed.

[Pete RimmerParticipant @peterimmer30576]

I don't think that the capacitor is designed to be switched out of the circuit, not by looking at that circuit diagram anyway. Two leads come out of the motor and go to only one switch terminal (one with the cap in series). This suggests that the cap and start winding are always live with the run winding.

What's not apparent is how the contacts are connected by switching.

[Les Jones 1Participant @lesjones1]

There is probably a centrifugal switch inside the motor that disconnects the start winding when the motor is up to speed. Probably an NVR switch such as this can be used. (There are also many advertised on ebay.)

Les.

[Phil WhitleyParticipant @philwhitley94135]

If the motor runs when you press the contactor in, there is nothing wrong with the motor, capacitor, or the centrifugal switch. Something in the starter circuit is the fault, like the start button, or as above, the coil in the contactor is open circuit, or the stop button, which should be normally closed, is not! can you post up some pics of the controls and switches etc. If you had to press the new trip switch in and hold it to get the motor to run, the new trip switch is faulty, once pressed in, it should close the circuit and lock in with a click.

Phil

[Ed DuffnerParticipant @edduffner79357]

Assuming it is a multi pole switch, I think only the 3 right-most contact pairs would be normally open and the far left pair is possibly just isolated connection posts (or there would be a direct short L-N if they were closed).

A centrifugal switch could switch between the capacitor or the solid wire to complete the neutral side of the circuit. Not sure if it would be a start or run capacitor.

Ed.

[Marischal EllisParticipant @marischalellis28661]

All

What a wonderful collection of thoughts and ideas. I am tied-up tomorrow but will sort out answers for everyone later in the day. Mean while a big thank you to you all.

M

[Marischal EllisParticipant @marischalellis28661]

Here is a couple of shots of the controls.With the 'electro' coil 'thing' pressed in, I get ohms across each two terminals on all four 'contactors', but when with not pressed in I get nothing. However, if I press the trip button I get ohms at contactor 4. that serving the capacitor. Not much the wiser I am afraid. Look forward to your thoughts. I am happy to start again and fit modern kit as long as I understand he wiring and so on.

[Les Jones 1Participant @lesjones1]

This is my interpretation of the wiring.

Contacts 3 to 7 and 4 to 8 must be working as the motor runs while the start button is held in, (The start button just pushes the solenoid in,)
The fault must be the coil is open circuit or contact set 2 to 6 not closing. With the mains cable unplugged first measure the resistance between 1 1 and 5. You should get a reading of a few hundred ohms. Then connect your meter to 2 and 6, You should get a very high (Probably over range reading.) Then push the solenoid armature in. The reading should drop to close to zero ohms. Report the result of these tests.

Les.

[Les Jones 1Participant @lesjones1]

If the fault is the contact set 2 to 6 then it should be possible to get it to work by a small change to the way it is wired.

Les.

[Marischal EllisParticipant @marischalellis28661]

Morning

I've done my homework, but not sure of my results, so, whilst hoping for 10/10 I will probably only get 4/10 on a good day. I am beginning to know a little more so learning. Thank you everyone so far as it takes a bit to pick some of it up. Here are my results this morning.

contact 1- 5 ….thing.

contacts 2-6 …nothing.

contacts 2-6 with solenoid press in …nothing.

I have unplugged as always, but is that safety as well as something to do with possible continuity?

Best wishes all,

M

[Les Jones 1Participant @lesjones1]

I assume that when you say "nothing" you mean infinite resistance. If not what do you mean ?

What was the resistance reading between 1 and 5 ? (I don't understand what you mean by "thing".)

Les.

Edited By Les Jones 1 on 26/08/2020 17:43:33

[Marischal EllisParticipant @marischalellis28661]

Les

Thank you for answering and I'm sorry for being misleading. By nothing I meant no reading. Nothing came up on my meter. My reading stayed at 1 which is nothing to me. I hope this is a bit clearer and thank you.

Yours

M

[Phil WhitleyParticipant @philwhitley94135]

what do you mean by "the trip button" If you mean the overload trip, that should lock in when you press it, and stay locked in till the circiit overloads and trips, if it does not lock in when you push it in (try hard push) the the overload trip is faulty, and that is why it is not working. Try holding the o/l button in and pressing the start button to see if it runs. The overload trip should have continuity through it all the time. the button is to reset it after it has tripped.Please show the start and stop buttons on the diagram! If you have nothing between 2 and 6 when the contactor is held in, that is the fault, 2 and 6 are the circuit that hold the contactor "in" once the start button is released

Phil

[Marischal EllisParticipant @marischalellis28661]

Hi Phil

I am tied up tomorrow morning but will look and consider what I am being told so thank you for your respect. Probably mid afternoon. Trip is the overload button, which I think doesn't stay (is new). Stop start switches are mechanical action. But will check it all again, so thank for the moment.

Yours M

[Les Jones 1Participant @lesjones1]

I am even more confused. Are you using an analogue or a digital meter and if it is digital is it auto ranging on the resistance setting ? I don't understand the 1 reading. (You don't say if this is 1 ohm, 1 K ohm or 1 Meg ohm.) Normally on a resistance range with the test probes not conneted to anything or each other the meter would display something like ol to indicate the resistance between the probes is higher than the meter is capable of reading. If the probes are shorted together it would read 0.00. (If it is set to al low resistance range it can give a small reading of probably les than 1 ohm which will be the resistance of the test leads.) Does your meter behave this way ?

Note to Phil. This type of NVR switch does not have a normal start an stop button. The start button just manually pushes the solenoid to the closed position and the stop button just forces the solenoid to the open position.

Les.

Edited By Les Jones 1 on 27/08/2020 15:00:05

[Phil WhitleyParticipant @philwhitley94135]

Thanks for that Les, that sounds very piss poor to me, but makes sense when you read the diagram!

[Les Jones 1Participant @lesjones1]

Hi Phil, Many of these NVR switches do not even have a separate maintainer contact. If It turns out that the only fault is the maintainer contact (2 to 6) then I am going to suggest linking 1 to 4. I think it is unlikely that the 2 to 6 contact AND the coil have both failed.

Les.

[Phil WhitleyParticipant @philwhitley94135]

Agreed Les! That would work. it looks like the switches can be unclipped from the relay, I wonder if the box can be opened for posible inspection and cleaning of the contacts?

Phil

[EmgeeParticipant @emgee]

Les and Phil

I believe more information is needed from Marischal to arrive at a working solution, it seems all of your assumptions to fix the problem are based on Les's cct drawing, whilst it does look a strong possibility it may not be correct.
As Phil said if the motor runs up OK when the contacts are manually held then the motor is not the problem, and further said it will be the lack of a holding cct for the coil or open cct coil.

If Marischal could provide some ohm readings from the various connection points you would have a much better chance of sorting his problem.

This lack of information problem nearly always arises when non electrically minded folk post with their problems.

Emgee

spelling error corrected

Edited By Emgee on 29/08/2020 17:37:57

[Les Jones 1Participant @lesjones1]

Hi Phil,
I agree that it looks like the spring clip holds the contact assembly to the solenoid part. I did think about suggesting trying to remove the contact assembly but decided that springs and other bits might fall out. I have just seen Emgee's post (I opened another session to look at the NVR pictures again to avoid loosing what I had typed.) I agree that my schematic may not be correct. This is my reasoning. What I assume to be contacts 3 to 7 and 4 to 8 seem sensible to provide double pole switching to the motor. As the indicator light is connected to 1 and 5 it seems likely that the coil is connected between those two points. This left 2 and 6 which seem to be wired as the maintainer contact. I am trying to understand Marischal's readings. In his post at 11:12 on the 26th he says the reading between 1 and 5 is "thing" and the reading between 2 and 6 is "nothing". I assumed by nothing he meant open circuit but he has not yet told me what he means bu "thing". In his post at 18:22 on the 26th he says the meter stayed at "1" I initially thought he had a reading of 1 ohm (Or 1K or 1M) but I am now wondering if just 1 (As opposed to 1.00) could mean overrange on his meter. I am waiting for clarification on this.

Les.

Edited By Les Jones 1 on 29/08/2020 18:11:45

[Marischal EllisParticipant @marischalellis28661]

Hi everyone,

I am just back in the house so will try to answer you all. You have been thinking and doing work. I am most tired and am out again tomorrow most of the day but will get it done. My special machine!! I was making a bit more sense of your chat on, I think Thursday So thank you all. I haven't forgotten all your efforts. It is all a lifeline to me. I will give actual ohms readings and will check the several scales re the 1.00

Marsh

[Author]

Posts