Member postings for Les Jones 1

If you can open the motor it should be possible to reverse it. The mains is fed to one end of each field winding. the other end of each field winding is connected to one of the brush holders. To reverse it you need to swap over the connections between the field windings and brushes. This will probably involve extending the wires from the field windings to reach the opposite brush holder. It is possible that there are also small RF chokes and capacitors fitted inside the motor to reduce interference. If this is the case you will probably have to post pictures of the inside of the motor so we can tell you if this has any bearing on the way you swap over the connections.

Les.

You could try my suggestion by making a washer out of some thin metal. The hole size would be the diameter of the outer edge of the three grub screw holes.

Les.

Looking at the marks from the engineers blue in your post at 16:09 today the items are making contact more towards the centre. If the same clamping force was applied near the edge of the block it would have more effect at preventing rotation. I think I would be tempted to take a skim off around the centre of the tool post so that the edges were making contact.

Les.

Edited By Les Jones 1 on 14/11/2020 16:59:21

Is the threaded post a larger diameter at the bottom than the threaded part ? If so are you sure that the tool post block is not clamping against the step on the post rather than the top of the top slide ?

Les.

I have a Seig x3 milling machine and am totally satisfied with it. I bought this (And other items.) from Arc euro trade and found them a very good company to deal with.

Les.

Edited By Les Jones 1 on 11/11/2020 16:56:26

Hi Gene,
The idea does not use any current sense input on the chip. It uses the feedback input for voltage regulation. In both cases (Buck & boost.) the adjustable voltage version would be used. The chip adjusts it's output attempting to maintain 1.25 volts on it's feedback input. So by choosing a resistor at the bottom end of the chain of LEDs that gives a voltage drop across that resistor of 1.25 volts with the desired LED current and connecting that point to the feedback input means that the chip adjusts it's output voltage to a value that gives a current through the LED chain that produces a drop of 1.25 volts across the resistor at the bottom of the LED chain.

Les.

I have used cheap step up switching voltage regulators (Based on the LM2577S) modified for constant current output. This is a link to the modification **LINK**
The same principle could be used with buck regulators The disadvantage of this idea is there is a 1.25 volt drop across the current sense resistor. This is not much of a problem when driving a series string of LEDs but for driving a single LED it wastes too much power.

Les.

The most likely failure mode for SCRs is anode to cathode short circuit. Looking at at the devices the way they are mounted on the heat sink and with the pins facing down the centre pin is normally the anode and the left hand pin is the cathode. This is the layout for most SCRs in TO200 packages. It would be a good idea to confirm this by looking for the datasheet for the devices used on your board. you can normally find the datasheet using Google or other search engines. Just do a resistance test between anode and cathode with both polarities. Both readings should show over range on your meter. (Or at least a very high resistance.) If they are short circuit you will get a reading of almost zero ohms in both directions.

Les.

I suggest that you also check the two TO220 devices which I suspect are SCRs. I think they form a controlled bridge with two of the three diodes. The output of this bridge will feed the motor. The third diode probably powers the control circuit that controls the phase of the trigger pulses to the SCR gates. The small toroidal transformer near the heatsinks will provide isolation between the control circuit and the SCR gates. If one of the SCRs is short circuit and it is not replaced one or both of the diodes that are part of the bridge will be destroyed again when power is re applied.

Les.

They are useful for drilling in confined spaces such as drilling up into a studded wall from under the floorboards. I have also use a similar one as part of a setup to cut a helix on my milling machine.

Les.

If you know someone with a small EDM (Electrical discharge machine.) that would probably work.

Les.

Edited By Les Jones 1 on 24/10/2020 11:46:54

There was an article in issue 156 (Autumn 2009) of MEW on page 15 about using "O" rings. I don't know if that is the one you are looking for.

Les.

Duplicate post.

Les.

Edited By Les Jones 1 on 16/10/2020 20:24:40

I too can't see how changing the the NVR switch can effect the problem.

Les.

We have now confirmed what I suspected in my post on 01/09/20. It has taken 41 days to confirm what would have taken a few seconds if I had been standing next to the band saw.
This is how I suggest connecting thing together.

It will behave slightly differently to the way it was connected in your original diagram, In your original diagram the micro switch was switching the full motor current which was more than it was rated for. It is now only switching the current taken by the coil in the NVR switch. This means that when the cover is open the motor will run while the green button is held pressed. The way it was connected the motor could not be made to run with the cover open.
It is now wired in a similar manner to the schematic in the manual. If you don't want to fit the lamp just don't connect it. (It will work without it.) Whatever physical changes you make to fit the new NVR switch the micro switch MUST be held closed by the left hand cover while it is closed.

Les.

This is still not the picture I asked for. From the second picture picture in your post at 12:46 on 11/10/20 it looks like the black plastic control box is mounted on the die cast right hand side of the machine and it looks like there is a hole in the hinged left hand cover of the machine that allows access to the red and green buttons, the hole for the key and the indicator light. It looks like the hole in the left hand cover does not go down as far as the plunger on the micro switch. I want to see the INSIDE OF THE LEFT HAND COVER so I can see if there is something on the INSIDE of the cover that presses against the plunger of the micro switch when the LEFT HAND COVER IS CLOSED. This would then explain the purpose of the micro switch.

Les.

It is the inside of the panel on the left hand side of the machine that I want the picture of. I think this is hinged at the back of the machine and opens to access the blade and drive rollers.

Les.

I have a suspicion that the cover on the left hand side of the machine covers the lower part of the original switch assembly. Am I correct ? Can you post a picture of the INSIDE of this cover showing area around the hole is for the original switch covering about 4 inches around this hole. I think there will be something on the inside of the cover that presses on the micro switch when the cover is closed. This is why I want to see the picture.

Les.

It looks like the motor is probably OK. Even if your mutlimeter has an AC current range it will probably be 10 amps maximum and the motor will take more than this when starting. This test was to ensure that the motor did not take a VERY large current that could destroy the new NVR switch. As it did not blow the fuse in the plug it is unlikely to damage the new NVR switch. We now just need to establish the exact purpose of the thing that you called a trip and DeWalt call a micro switch. It is a pity that you have disposed of the original item before we could establish if it was a thermal overload trip or just a NO micro switch.

Les.

I agree with Dave's comments. I am not going to draw a wiring diagram for you until we sort out the function of the thing you called a trip and DeWalt call a micro switch. I suspect that the item to the left of the KJD18 (NVR switch) is a emergency stop button. Can you post a picture of the front of the panel that it is on and also the side of this item so we can read the ratings ? (This is so I can decide between wiring it to break the full load or just the feed to the coil on the NVR switch.) Can you also measure the resistance between the connections second new micro switch both with it pressed and with it not pressed ? Can you also post a picture of where this switch is mounted so we can see if it is some kind of safety interlock ?

This is how to connect the motor directly to the mains to confirm that it is not drawing a very high current as I suggested in my post on September 10th. (This is to avoid damaging the new NVR switch if the original fault was caused by the motor.)

Les.