Z-axis Problem Bridgeport CNC serie 1

[Rufan]

I have the machine for some weeks. But never use it because of the problem.
When I get this CNC i have to pull of the head. In my garage I put it together. And then the problem starts. The wires on the limit switches are not market. So I find the wiring schematic for the switches and put the wires back on. But when I go down with the z-axis the quill decel switch don't response it still goes down. I measure the switch and it is good. The up/down limit switches are normally open.
Second problem when I operate the Z-axis up and down. One of the power transistors blow up. I put a new transistor. I operate the z-axis and after a while it blows up the transistor again. I read the service manual to see if I can find some solutions. I adjust the powers but still the same problem. I don’t know what to do anymore. Maybe you guys can help me with some tips.

Thanks in advance..

[machintek]

You are correct. There are three switches on the front of the quill. The top one is a fairly accuarte switch that stops upward motion. the switch just below it is the decel switch. It should make .200 inches before the top stop switch. If it does not, you will have mispositioning issues. Trust me. Bottom most switch is a overtravel limit switch. It is a normally closed switch, wired in series with the rest of the overtravel switches. Thus any one of these switches can shut the drives off by breaking open the string.

What is the AC voltage of the Z axis feed coming from T2 in the top of the back electrical cabinet? IE: wires 11 and 12 are the X axis, 13 and 14 are the Y and thus 15 and 16 must be the Z. I am doing this from memory. If it is greater than 64 VAC, you will blow transistors like candy. The only way to bring this down is to lower the power coming into the machine. What is the voltage coming in?
You did not mention which BOSS version this is. I wonder if it has the small SMS board. It is meant to try and limit transistor blowing when an axis is moving and it hits a limit switch or someone pushes the emergency stop switch.
Are you using 2N6547 transistors?
Is the static current set to 8 amps DC? Note never attach or remove a meter unless drives are off.
Are the DC axis fuses of the screw in variety? NOT good if so.

Well, that is a start.

George

[Rufan]

George thank you very much. I really don't know which Boss i have. Is there a way to find that out?
The output voltage (T2) wire 15-16 was 74VAC. I don't know why but somebody put wire 15 on the wrong output. Strange that it ever worked. So I put it back on the original place and its 64.4VAC. Now I have to buy a new transistor. I use BUX48 or BUX98. In the x-axis I also use BUX48 and it works fine. I temporally put a BUX88 in it but it does not work very well, it no move very smooth. The transistor is still good. I moved the axis a lot up and down.

But my switch problem is still there. I put them like you said. I connected the bottom switch to normally close. When I turn the machine on I can not clear the override switch on the control panel, only if I manually push the bottom switch to open. Temporally I put it to normally open. I go with the z-axis up, the decal till the decel switch is activated and it works. The axis goes very slow upwards but it does not stop when the top switch is triggered. I take a look in the wiring diagram and start measuring. It’s totally different. In the wiring diagram all the wires from the switches are going to K5 on the XDI board. But when I measure, the up and decel switches going to K5 and the bottom switch to K6. So if you have any suggestions about this, that will be nice.

[machintek]

That is a lot better for the T2 voltage. Sometimes people cheat to get more energy to the Z axis by moving that wire to the next higher tap. This usually means that the power at their shop is low to begin with.
What boards are in your machine?
ZDI, ZCK, NTP, etc means a BOSS 6.
RCK, XDI, LSI-11 with 5 big ICs means a BOSS 5.
RCK, XDI, LSI-11 with 4 big ICs means a BOSS 4. This is not written in stone. Boards can be mixed up. The ERS part number will tell me a lot.
Then I can look at some schematics.

George

[Rufan]

I have a RCK, XDI, ERS and LSI-11 boards. The LSI-11 has 5 big IC's.
The part nr on the ERS board is 1927990. It is the one with the S1 switch.
Are you also familiar with the RS232 downloading kit? Do you recommend buying one of these kits or can you make it your own.

A lot of thanks George.

[machintek]

You have a BOSS 5, based on the boards in your machine and the part number of the ERS.
I believe that the RS232 kit is a good idea for many reasons. Have you ever made a cable? It is time consuming, let alone trying to find the correct AMP plug and pins. Then there is the software end. Trust me, go for the kit.

George