I am having problems with x-y axis on my boss 5 machine. The axis will not move the motors will whine but not move. I have moved the smd boards around with the z axis and nothing different. I check current at fuses 12-13-14 to be 8.5 amps. Voltage at these fuses static 9.5 volts. Voltage when trying to jog axis is 13 on x-y and 80 on Z. Any ideas? Also anyone have wiring print scanning that they are willing to send to me. I have ordered the manual but not here yet and I need this machine asap. Thank you for your help.

A. Thayer

Sound's like a transistor has blown, fairly common promblem I'm lead to belive.
have a look at this thread.
http://www.cnczone.com/forums/showthread.php?t=8508&highlight=2N6547

First: DC amps too high. Set to 8 amps. Remember that the meter (unless it is a DC current clamp) puts a burden on the circuit due to the fact that it has a shunt (it actually measures the voltage drop across a known precise resistance and converts it to a current reading). When the meter is removed the current will go up.

Put the machine in "step." Push the direction switch. Each time you push it, the mechanical counter should move .001 inches. It moves forward and backward you do have blown transistors. They usually short so they cannot turn off. The whine you hear is the stepping motor oscillating between poles.

At transformer T2 in the back, measure the AC voltage at wires 11 and 12. This should be the first and fourth wires. It should not be more than 63 VAC. If it is you will blow a lot of transistors.

Read the old posts. What I have said here is nothing new.

George

Is there such a thing as a leaky transistor or a weak one. I would like to know what to purchase for transistors and where I can find them.

Very rare to have a half good transistor, but I have seen all sorts of odd transistors in machines. Bridgeport specified 2N6547 trasistors. I have heard of others putting their spin on what to put in. What I do stress is that all 4 for a axis be the same.
I would try Newark electronics, Allied electronics, or Digikey. Alan at my office has a pile of them as well (1-800-245-2598) but shop around for the best price.
ON a side note, I have seen screws and washers fall between the diodes at the bottom of the door as well as between wires on the terminal strip for the motors. These will also create a short that will imitate a bad transistor.
If you have screw in fuse holders for fuses 12, 13 and 14, they develop a high resistance and also cause a lot of problems.

George

I have found a transistor at radio shack that is NPN 115 watts at 100 volts and 15 amps. I would like to get my machine running for the weekend and I would like to know if these will work for a short time until I get the others that I have ordered? Also anyone else use any other transistors for one of these machines that hold up better.

George
When replacing the blown transistor is it worth replacing all 4 transistors at the same time?
How often do they go, the first one went on my machine this week but I've not had it that long, so is it worth buying 12 transistors if I intend keeping the machine for a while?
These are the cheapist I found in the U.K. http://www.dalbani.co.uk/catalogue/product_details.php?id=1118

Cheers

Chris

Chris, at 2 pounds each, that is dirt cheap. I believe Bridgeport was charging 25 dollars each. What I suggest is that all 4 be the same, including the same make. Usually these short emitter to collector, so the good ones can be moved to complete another axis (assuming that they are the same). Then set your current.
I have machines in my territory that have not blown transistors in years. If they blow, there is a reason.

George

I have been using ECG-53 transistors for a long time and they last a lot better than the 6547's. I get them from Masline Electronics in Rochester, NY (716-546-5373) and the last time I bought any they were about $8.00 each. I used to replace all four transistors on a module, but it got too expensive, so I test and only replace the bad one. (That is, after I had converted all of the modules to all ECG-53's) I check with an ohmmeter, in-circuit (after removing the suspect module from the machine), and basically look for gross differences in the resistance between legs (I test all three "pairs", forward and backward). This is a lot easier than trying to completely disconnect the transistors and checking them. A shorted transistor will read very low or no resistance in both directions on at least one pair of terminals, an open transistor will read a lot of resistance in both directions on at least one pair. A "weak" transistor will be quite inconsistent with the others, and I always replace them while I'm at it. I keep a couple spare modules on hand and always have one ready to put in when I have a problem, then I can take my time and replace the bad transistor(s) at my leisure. If anyone needs a spare module, I have a couple surplus ones (no guarantee on the condition of the transistors), that I would sell for $25, shipped anywhere in the US. E-mail me off list at mercat@clarityconnect.com to buy one.

Thanks George I'll order a few then and replace all 4 as there is allsorts of makes in there at the moment.

A few more questions.

What heat sink compound do you recomend or will any do?

And do you need to put it on the block before fastening it back on to the large heat sink on the door?

Cheers

Chris

I have done a lot of research for heat transfer paste (for my PC processor where I use Artic Silver 3) and the best ones have a high silver content. But this does not do these transistors any good as you will have a rubber coated fabric as an electrical insulator beneath each one. I prefer the old mica insulators. I do not believe these insulators help heat transfer. Therefore any cheap heat paste will do.
I assemble the blocks including soldering, install them on the door, and then attach the terminal strip wires.

George

I have always used the heat transfer paste on the surface where the module meets the major heatsink mounted on the door. I have also always tried to replace all of the mounting screws, despite being in a hurry and inevitably dropping one or two down into the innerds of the lower door. If a spot gets too stripped out to hold well, I just slide the module up or down a little so I can get good grip on the screw threads (which ain't all that good to begin with). I operate on the theory that the screws were put in for a good reason, so I don't leave any of them out. I know some people get so frustrated with them that they end up with only 3 or 4 holding the module, but that seems to me to be counter productive. Fewer screws, less heat ransfer. Less heat transfer, more blown transistors, ergo, more frustration.

I ordered some transitors but they no longer stock them, so I tried another company they and got the same reply from them as well even though the website said they where in stock, great.
Ended up ordering them from the States here (even cheaper) http://www.futurlec.com/TransPower2N.shtml

Cheers

Chris