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  1. bfhamr

    3 phase motor test.

    Were the voltage readings taken while the pump was running under load? If not it might be a good idea to check it. I've seen a couple instances where the wiring was too small for the size motor being run. Dan
  2. bfhamr

    Fluke Scopemeter?

    Anyone have any experience with these? I'm looking for a portable scope to use on CNC equipment. I have a Tek TDS3012 already but would like something a little more portable. This would probably knock around in my truck until I had a need for it. I leave my Tek at home currently and only...
  3. bfhamr

    failing transistors

    Yes, I have checked the return line for the flyback diodes. I don't believe the problem is with the board unless it was designed poorly. Three identical boards have failed. I'm thinking the problem is external to the board. dan
  4. bfhamr

    failing transistors

    Sorry I haven't posted for awhile, the project is currently on hold. The customer isn't sure he wants to sink any more money into the repair of this machine. He is considering replacing the machine. To answer a couple of questions: -The low voltage supply is unregulated. It consists of a...
  5. bfhamr

    failing transistors

    I've talked to another EDM supplier who sells a nearly identical machine (it has the same circuit board). One of their engineers told me that the control voltage, when loaded, will drop to +/- 8 or even +/- 7 volts. I may be able to get a scope on the board. At this point though the...
  6. bfhamr

    failing transistors

    See here for a copy of the schematic. http://i100.photobucket.com/albums/m18/bfhamr/DSCF0369-1.jpg Also I was wrong, the transistors are switched in banks of 3 not 6. dan
  7. bfhamr

    failing transistors

    stupid question, how do I attach a picture, or do I have to supply a link to it. dan
  8. bfhamr

    failing transistors

    After a bit of searching I was able to find a schematic of the circuit board. I'd post it but I don't have any way of scanning it. I could take a picture of it if anyone is interested. The last time I was able to work on the machine I noticed that the negative side of the +/-8 volts was low...
  9. bfhamr

    failing transistors

    I've tried tracing out the circuit on the board which has all 6 transistors. The 6 are controlled by 1 transistor, but that one is also controlled by several others. I've not been able to completely trace things out. Not being an EE, what may be a familiar circuit to you, takes me awhile to...
  10. bfhamr

    failing transistors

    itsmoked, I would agree that a drive problem could explain the failures except that one of the boards (with the 6 transistors) has 2 of the 6 transistors still working perfectly. Wouldn't all of the transistors fail? Maybe it's justs coincidence that 2 haven't. dan
  11. bfhamr

    failing transistors

    I've gotten a little more info. -The transistors are not getting hot, only lukewarm when touched. All cooling fans are working. -The transistors and the associated switching circuitry are all located on the same board. This board has been replaced and has failed since being replaced. -There...
  12. bfhamr

    failing transistors

    I don't believe the burnout will be sequential, the T's are seperate with their own seris resistor. They are then in parallel with the electrode. I'm wondering if maybe the "kick" from the wire wound resistors may be whats causing the problem. There are diodes in the circuit to bypass reverse...
  13. bfhamr

    failing transistors

    For those of you that don't know what EDM is, it is a spark erosion prosess. An electrode is brought in contact with the part to be machined. An arc is established and the metal is burned away. The machine controls the arc and moves the electrode up and down to maintain the arc. More power...
  14. bfhamr

    failing transistors

    Sorry for the lack of info, I guess I was looking for general info. I'm not in front of the machine, actually I'm in the office which is an hour away. Here is what I know about how the machine works: --power is supplied to the transistors in question. --the transistors are switched on...
  15. bfhamr

    failing transistors

    Newbie here. I repair machines for a living, I'm currently working on an EDM. Normally I would contact the manufacturer but I'm told they are no longer in business. The machine has a set of 6 transistors (Hitachi 2SC1343). These can be switched into and out of the circuit depending on...

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