BP Boss 5, Z-axis quit, help me please!

[rsr911]

Thanks George,

The machine does have push in fuses. Somewhere along the way here I lost a transistor on the Y axis as well so I can't compare that one right now. Earlier I was getting 3.9-4.5 volts on both the X and Y (they were very close, I think 4.3 and 4.4), the Z was giving me millivolts and floating all over. Now I measure 3.95 volts at the X, 1.65 at the Y, and still millivolts at the Z. Prior to losing the Y axis I adjusted the amperage on X and Y down from 8.6 to 8.2 on the ACC board.

The transistors that went bad are shorted to ground internally. Judging by what you've told me as well as reading the manual I concur that it points toward the rectifier. Problem is since the fuses have been updated there are no longer terminals 31,32,33. I assume these are X,Y,Z. The manual mentions checking the rectifier between 31 and 39, 32 and 39, 33 and 39 as well as a terminal on the tranformer output. Can you explain that procedure a bit, I'm not certain I understand it correctly. Do you know the part number for the bridges, perhaps tommorrow I can find out if they are available localy. I did replace the SMS board, didn't make a difference. I didn't bother with the other boards. Tommorrow I'll put new transistors in for the Y-axis but I'm concerned as to why they blew out.

[rsr911]

George,

Here is where I am at. I check all the transistors and found 3 that where definately bad. I've replaced those and all three axis are working. Most of the good transistors were a little over or a little under 0.5v some as low as .480 but they are working. I also checked the regulators following your method and I got in the 0.451-0.464 range on all tests, nothing tested at the 0.5v you suggest. I started up the machine and ran a check of the X,Y,Z voltage. My earlier numbers where to what I thought was a ground but was not. I got 12.25 for X, 14.20 for Y, and 10.00 for Z. Next I will shutdown and test the amperage at each fuse. To be on the safe side I'm going to shut down and pull the fuses one at a time firing up with the DMM across the fuseholder. I'll adjust to 8 amps on the ACC board. What should I do about the range of voltages at the axis?

[machintek]

You do not have the meter on OHMs but on diode test. It is measuring the voltage drop across the semi-conductor junction. All those readings are good as they are close to half a volt. A germanium junction has a different voltage drop. I believe it is closer to .2 volts.

The voltage at standstill is a function of the type of transistors you have put in and the current setting. I do not believe you are using Motorolla 2N6547 but generic replacements. Am I right or wrong?

George

[rsr911]

George,

I've got a mix and match of 3 different kinds in there right now. It's the best I could do with the used spares I got with a bunch of boards off ebay. My plan is to buy a good set and set them up on the blocks ready to go into the machine. Given that I work full time and only have limited time for making parts on the CNC it's worth it to me to spend a little to insure less down time, plus this way I can just swap out transistor blocks when I have a problem.

I notice my machine has diodes across the transistors terminals but my spares do not, was this an upgrade and should I include them in my spare blocks?