Transistor Blew Again!!

[ranchak]

The same transistor blew again on my Boss 5, is this a coincedence or do I have to look at something else?

[valmet58]

when you changed the transistor did you check the current that your motor draws??

[machintek]

Voltage out of T2 cannot exceed 63VAC.
Current through fuse 13 cannot exceed 8.2 amps.
Does your machine have a SMS board?
Do you have screw in fuse on fuses 12, 13, and 14?
Do you have a loose wire somewhere?

George

[WGoyer]

I didn't see the original post, so I'm guessing that you keep blowing your stepper drive power transistor.

My experience with them over the years is that
1) You really need to be sure you have a sturdy replacement if you've cross referenced it.

and

2) Forget the socket. I don't think I've ever gone back and changed one if I just solder the transistor into the socket. The poor springs in the sockets are notorious for not holding on tight to the emitter and base leads. If there is anything left of the socket, solder the new on in. Otherwise, buy a new socket and solder the transistor into that.

Then, button it up securely, because that's the last time you'll have to mess with it.

Warren
www.uptimecorp.com

[ranchak]

I replaced the bad transistor and the other three. I figured while I'm in there I might as well change them out. Tried to run the axis and nothing. I checked the transistors and the same one was blown as well as another one!

I did not check the voltages and current yet, but I will do that tomorrow. I guess I need to order some transistors and maybe some Geckos!

[ranchak]

Voltage readings at T2

Line 12 44.4 VAC
Line 14 39.1 VAC
Line 16 26.4 VAC

Line 12 and 14 56.2 VAC
line 14 and 16 76.9 VAC


Fuses 12,13 and 14 are FNM style fuses

Fuse 12 8.8 VDC
Fuse 13 7.9 VDC
Fuse 14 8.6 VDC


I'm pretty sure I do not have a SMS board.

2.4 Amps is the max current I read through Fuse 13.

Any suggestion as to where to look for a loose wire?

Thanks again, Ron

[machintek]

The way the transformer is wired is that from the left, you probe the 1st and 4th terminal, the second and 5th terminal, and the 3rd and 6th terminal.
This corresponds to X, Y, and Z. I have seen people screw this transformer all up trying to single phase it and try and get more power by going up to the next set of terminal. None of this is good.
Anything over 63 VAC will cause blowing of a transistor.
Unless you have a DC current clamp, the drive is shut off, the meter is attached set to DC amps, and the drives are turned on. Normal is 8 to 8.2 amps. I leave it at 8 since the meter has a shunt that puts a small burden on the circuit. then you shut off the drives and disconnect the meter. If you do not have a SMS board the current will drop like a stone. With a SMS board it will drop to about .5 amps and drop gradually. Usually transistors turning off blow. Not turning on.

George

[ranchak]

Transformer Voltage

X Axis 36.9 VAC
Y Axis 73.4 VAC This is the axis I am having trouble with
Z Axis 36.7 VAC


I can't measure DC Amps.

[machintek]

You need a better meter to work on this machine.
How is this machine powered?
3 phase from the wall? Phase converter? What is each leg phase to phase and phase to ground?
What does the name plate on the back of the machine say the original configuration (voltage) was?
Something is very screwed up at T2.

George

[ranchak]

Thanks for your help George. I have decided to switch over to Geckos and a board from PDMX. I feel this is the best thing for me.