Blown band saw circuit.

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

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

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

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

I have just been reading through the thread again. I had misread the first post and thought that the motor ran when the start button was held pressed but you actually said when the TRIP SWITCH was held pressed. All I have said so far is not relevant. If you have to keep the trip switch pressed in then the motor is taking too much current or you have been supplied with the wrong current rating of trip switch. (You should never hold a trip switch in as it is designed to remove the supply id the load is taking too much current.) Sorry for my error in reading your first post.

Les.

Have just read about your problems.The fact that you can hold the contactor in and your motor runs definatley sounds like the coil is faulty

Good luck Brian Morehen

Back home this afternoon and have the following to report. I am so sorry if I am misleading everyone.

With everything as is, ie nothing disconnected or pressed in, I got the following. The digital meter reads 1. but will, when placed against terminals read various Ohms before very quickly reducing down to O. It moves very quickly so it is not easy to read the fractions to three places. If I connect the two probes together it will read 0 Ohms..

Terminals 4 to 8 - 4.22 Ohms reducing to 0. Reading can fluctuate a bit but possibly down to my technique.

3 to 7 - no reading. Meter did nothing.

2 t ditto ditto

1 to 5 ditto ditto

Across the reset button, both in and out, nothing happened in terms of physical action, that I could feel, so no reading possible.

With the coil pressed in.

Terminal 4 to 8 4.2 or 3.7 Ohms. There was variations on the start of readings.

3 to 7 no reading. Meter did nothing.

2 to 6 ditto ditto

1 to 5 ditto. ditto

Over the capacitor terminals I got readings of 2.66 Ohms.

Les, you noted a NVR switch may possibly be used. If this present stuff is all too mixed up, I would be happy to go down that route; all things being equal. Looking at my saw bench which has an NVR it seems OK with the reset button wired in but no allowance of a capacitor.

I could possible separate the coil and contacts as there is very little to show connected between them, but I would need to be very careful of the return or hold back spring on the top, but cannot see where things would spill (or spring) out of.

I have ordered a replacement reset button which should be here in a few days as the 'was new' switch is definitely not right. It is not functioning even as it did last time when I tried it. Hope I being more helpful this time around and my information is less misleading.

Marsh

Hi Marsh,
It looks like the "1" reading is your meters way of indicating over range. (Open circuit.) I now have confidence in the resistance readings in your last post. They seem to indicate that the schematic I drew is wrong. If it was correct then without the solenoid pressed in 4 to 8 should be open circuit (Your meter reading "1".) and with the solenoid pressed in it should have read 0 ohms.Can you confirm that it was the overload trip button that you had to hold pressed to get the motor to run after the initial fault ? (NOT the start button as originally thought.) Have you checked that the motor is free to turn by hand ? What is the mains voltage in your country ? (I am thinking that if it is 110 volts Then a overload trip for the 240 volt version may have been supplied. This would be about half the current rating required for the one for 110 volts. You do not need to worry about about the capacitor. It is wired the same way as it would have been wired if it was strapped to the motor. The NVR switch I linhed to is a 240 volt version but you may need a 110 volt version.

Les.

Hi Les

The motor turns fine. When I Impressed the rest button which when held in let it all turn 'as normal' or at least it seemed like that. I pressed the reset button the motor turn quite OK it seemed. The reset switch was correct rating and so on. A 240 rating for the NVR and a 16 amp rating would be OK.

M

Hi Les

The motor turns fine. When I Impressed the rest button which when held in let it all turn 'as normal' or at least it seemed like that. I pressed the reset button the motor turn quite OK it seemed. The reset switch was correct rating and so on. A 240 rating for the NVR and a 16 amp rating would be OK.

M

I have now found the manual for this saw here
**LINK**

It includes a schematic but does not seem to be quite the same as I suspected. It does not show the item that Marsh calls a "Trip switch" which he shows directly in series with the input live feed. I had assumed that this was a thermal overload trip switch. The schematic does show a safety micro switch which only breaks the feed to the contactor coil. The manual also shows that there is a safety key which has to be inserted to start the saw. I am now wondering if the thing that Marsh calls a "trip switch" is this safety micro switch.

Marsh, Can you confirm that your saw does NOT have the key that is shown in the manual ? With the "trip switch" not connected can you measure the resistance between it's contacts with it not pressed and also with it pressed.

Les.

Morning Les

I looked for a manual years ago but couldn't find one and similarly a few weeks ago so wonderful you have found it. A big thank you. I have now printed it off.

I have looked at the elect diag. (top right hand) and they do seem to be a bit different. The safety micro switch looks to connected in another way but that may be convention. So the micro switch is the trip switch or the reset button it seems as I have called them. Looking at the diag. the micro switch (26) looks as if they are the same shape, etc.. The key is a manual plastic wedge key which when inserted or pushed in mechanically allows the start button to move in..

The readings for across the trip (micro) switch are as follows; button 'pressed in' the resistance goes to about 6.9 reducing to 0. For button 'not press' in there were no readings. The teleswitch is the contactors.

Thank you once again. The diag.is a big help. I hope this is helpful.

Yours Marsh

Hi

I have been thinking! ..........I have tried to do a new circuit using the same or similar switch as on my table saw. The reset button is at the bottom as saw and I have added a capacitor to suit band saw. Would possibly bring controls up to date and make them future proof a bit. Yours

I should have said wiring was so much easier when there was a red wire and a black wire. What could go wrong!

Yours

From your test on the switch that you call a trip switch and DeWalt calls a safety switch it just seems to be a normally open push button switch. The way you show it connected in your first post it must be in the pressed position for the saw to work. Can you post a picture of the original switch that was saw when it failed showing any printing on it. From the description safety switch I am wondering if it could be an interlock switch to ensure the cover is closed for the saw to work. If this switch is intended to be pressed manually is the a label next to it ?
The KJD22 NVR switch should work but it does not have the key function.

Les.

HI

Yes it is the safety switch. The name trip switches must be from another earlier era.? I think it is an open press button. The writing on the switch is almost too small to see and the photo didn't work, so I have written it down. I am tidying up so must have thrown the old (original) switch out I am afraid. They were the same from a DeWalt replacement. I have another coming in the next day or so as it has been posted out. I don't think it is an interlock switch . No writing ever near it. Here is the very small writing on switch.

12A 125-250V AC

1/5HP 125 AC

1/2HP 250 AC

R 84

This is how it is written out. I will look further at the NVR switch (on my table ) similar to the one you suggested earlier just in case! A lot more wires on it than than I thought. With every best wish. Marsh

With that micro switch connected as in the diagram in your first post or connected as in the drawing in the manual the motor can't run unless that switch is closed. (For it to be closed it must be pressed from the results of your test in your post at 12:20 on Sept 01.) Can you confirm that your diagram in your first post shows correctly hoe the micro switch is connected ? The KJD22 NVR that you showed in a previous post and the 4 pin version are available from this supplier.
**LINK**

Either version could be used with your band saw. According to the manual versions of your band saw for some countries do not have the micro switch fitted. This is probably to comply with the regulations for different countries.

Les.

Hi Les

It is or was wired as my diagram with the micro switch as shown. I suppose I don't really need the micro switch anyway if other countries don't call for it, and the white running light which didn't work previously as I only work on my own and don't need a visible warning of running. Perhaps I should think more seriously about a new switch but I will take you advice please. They don't cost too much. I will sleep on it tonight or am I being a bit slow here?. Thank you so much for what you are doing and more.

Marsh

When you receive the second new micro switch test it with your meter BEFORE fitting it to the saw to see if the results are the same as you reported in your post at 12:20 on 01/09/20 for the first new switch. Do you have a way to measure the current taken by the motor ? I expect the running current to be about 5 amps but the starting current will probably be over 20 amps. (It would probable draw the starting current for less than a second.) If you do then I suggest connecting the motor directly to the mains with a fuse in the circuit. (If you are in the UK then the 13 am fuse in a 13 amp plug will serve the purpose.) The reason for this is that I suspect the motor may be drawing too much current which has damaged the NVR or the original trip switch. In one of your posts you said that the resistance across the capacitor terminals was 2.66 ohms. This is actually the resistance of the two motor windings in series. This value seems low for that size motor.

Les.

Hi Les

I will check in the morning. I hoping the micro switch may come tomorrow or Saturday in the post. I have to omit I have ordered a new NVR start switch and it is the one you suggested (poss) would work a week or so ago. So may come in the coming week. Thank you for all your thoughts. Write tomorrow.

Marsh