Boss 6 diodes

[TPMX]

I found a little info today on checking the diodes for each axis on the panel behind the SMD boards on the heatsink.
I checked all of mine by going from the screw to each side of the diode and have 1 that shows a direct short.
My question is will just 1 of these bad keep the machine from moving in all axis or just the 1.
My bad one is in the x axis.
My steppers go locked when i do the limit reset(I see they should)but will not even try to jog.
THANKS

[afmcorp]

hello

yes even 1 will shut the axis down. the proper way to test is to use the diode test on ur vom [digital] to see if it beeps indicating a short or a connection. no beep and ur fine. you can by reversing the test leads also read the diode. i find a reading of 540 or so is good reverse the leads and they should go to 600 or so. when u test the diodes if i find one that is say 515 i'll just replace it for gp. you can get 2645n from newark electronics. also be sure to replace the isolation pad even if they look good.

[HillBilly]

If you are talking about the diodes on the output transistors, You may be seeing a shorted transistor if it is still in circuit.

This will only keep the affected axis from jogging.

Darek

[TPMX]

I am checking the ones behind the smd boards.
THANKS fro the replys!

[afmcorp]

tpmx,

i should have mentioned the proper way to test these diodes is on the pin to pin.

i have 3 boss 6 style, one centroid and my r2e3 boss 8 w/servos. i generally keep about 20 or so of the boss 6. they blow all the time. i have extra mounts so it only takes us a couple of minutes to change them out.

all of our machines are still cutting accurate. of course we've been working them 15 years and kinda know them by heart and their tricks. i see no need to replace them yet. i did buy a small VMC with a 10 pc tool changer about 7years ago. still haven't had to replace any of the bosses so i've never made a part on the blue machine. but someday i'll get aroundtuit.

good luck and let us know how u make out

[TPMX]

Can these be checked in the circuit?

THANKS

[afmcorp]

yes
pull the smd boards showing all 3 units POWER OFF ONLY

now just go across the pins 1 diode at a time x, y, & z boards.
if u get a beep you have a bad diode i think it's n2647 call newark electronics they have them don't forget the insul pads don't have to be white may be clear

if u don't have the maint manual for boss 4 thru 6 u really should get one. you'll see how easy this is.

good luck

[HillBilly]

I am still wondering which diodes you are checking. The ones amfcorp is refering to are large, bolt down on one end (hence the insulated pad.) and soldered to on the other end.

The ones I am thinking of are the size of a 1/4 watt resistor, soldered on both ends and are across the base to emitter of the output transistors.

Darek

[TPMX]

Sorry Darek I see what you are asking know.
I am checking the large ones.
I found 1 bad on the x axis.
I will need to replace it but still must have a larger problem.
If you remember I posted some on this machine back when I got it.
I have the machine now where it will power up with the red overtravel light on.
I can press the button,the light goes out and I can here a couple relays come in.
The spindle will run for/rev the brake works and the spindle up/down works.
There is no error light.
The steppers are all 3 energized(locked) but that is all I have.
Redouts just show all zeros.Machine will not jog or even try to move.
Running out of things to check and about ready to retrofit.
I talked to Darek about his board but am afraid it may not get things going if this is a drive problem.
I am open to opinions from all.
THANKS in advance to all!

[HillBilly]

If your readout never changes from ZERO then the BOSS computer is not outputing pulses. Each axis has two signals going to it. These signals come from the K8 plug of the XDI board (or ZDI for BOSS 6). I have included a diagram. If you disconnect this plug and enable the machine you can jump one of the axis signals to groung and that axis will move one increnent, it should also move back one increment when the jumper is removed. One increment will either be .001 or .0005 depending on your machine. The drives accept phase signals instead of step and direction so the pattern would be like this:

00
10
11
01

Darek

[TPMX]

Thanks Darek,I will try this but want to make sure I do it correct before I do it.
Do I want to jump #1 to #2 for x-#3 to #4 for y or #5 to #6 or do I want to jump to ground?
I am no electrician so I want to make sure.
THANKS

[HillBilly]

You want to jump to ground. If you ground pin 1 then remove and then ground pin 2, you should see 3 steps on the X axis (0 to +.001 to 0 to -.001). These inputs are pulled high by 5.6k resistors on the SMD boards to the 24 volt supply. The completed circuit should only draw about 5mA.

Darek