Bridgeport BOSS 5 Transistor

[rogerfries]

I have an old BOSS 5 in a home shop. It's controlled with Mach 3 and a hillbilly BOB. I've several times had the famous transistor blowing problem. I thought I solved it by moving the artificial leg of my rotery phase converter to L3. While this helped I just blew another one. I E-stopped it during a rapid move I've read that that can cause the problem. As the transistors seemed to test good with the meter, I had to relace all 4. After spending a few hours of "Quality time" on the floor behind the machine replacing transistors the machine is working again, but I'm not enjoying replacing these things!

I've spent hours reading about transistors in the Zone, but much of which I don't fully understand. Also some of what I'm reading seems to be theory.

Is there a solution to this problem, or should I just scrap the rest of the 1980 electronics and go to Geckodrives or something else? I'm willing and able to spend the money on the Geckos if necessary, but....

Thanks! This whole machine would be at the bottom of Long Island Sound by now if not for all of the great information i've gotten here in the Zone.

[machintek]

Wow, between 1982 and 87 I used to cover Long Island. I remember some hurricane damage way out at the end one year.
Are you still using T2 for the drives? I have found that if the output of T2 is over 63 VAC, you will blow a lot of transistors. Also do you have a SMS board? It has 3 diodes, 3 resistors and 3 fuses on it. Bridgeport added that board to assist in preventing the current from dropping like a stone on E-stop. Lastly is the static DC current less than 8 amps?

George

[rogerfries]

Thanks for the reply George, I do have the SMS board, but I'm not not sure if T2 is connected to the drives, nor do I know what my static DC current. Can you tell me how to check this. I do have a good multimeter if you can tell me where to check.

[machintek]

This is why I do not typically answer questions involving conversions since I am not familiar with them. I gather that your set up uses the final drive transistors. Much more than that I do not know. My answer was in case you were using that large transformer in the top of the back cabinet. The current to each axis is typically measured at the DC fuse (12, 13, and 14). Drives must be off when pulling a fuse or connecting/disconnecting a meter. Otherwise you blow more transistors. Current is set by the ACC board.

George

[creep_pea]

George
The HillBilly conversions use the original drivers as standard, the only thing they replace is the computer side of the machine so all the computer rack comes out and the 12v 5v power supply, this is replaced with a PC wired in to the K8 K6 and K5 plugs so the drives remain totally as original.

[rogerfries]

George,

My setup is exactly as Creep pea described. Thanks for the excellent description I would not have explained it so clearly.

I performed the tests that you suggested. My current was 8.41, 8.21 & 8.78. I addjusted them all to 7.95 by using the pots on the ACC card as you suggested.

My T2 voltage is 74 VAC assuming I tested the correct terminals. That's 17% higher than the Max 63. Sounds like that may be the problem? How can I get the voltage down? Is this due to my rotary phase converter? My voltages are L1=122, L2=121 & L3 = a wopping 181. Ay Ideas how to correct this?

Thanks!

[machintek]

Both contribute to your problem.
The only way to adjust T2 voltage is to reduce the voltage coming in. Buck/boost transformers MAY be a way to do it. Talk to your electrician.

George

[rogerfries]

I just spoke with a rep from TEMCO. They sell Buck/Boost transformers as well as rotary phase converters that are built for CNC machines. He recommended that I replace my phase converter with one of there CNC phase converters that will deliver clean balanced power to the machine.

This leaves me with two options both at about the same cost. Which is the "better" way to go.

Scrap the 30 year old electronics and go with Geckodrive G203V's
Or buy a new regulated phase converter and keep the 30 year old stepper drivers?

Or any other option I haven't thought of yet.

Thanks!

[creep_pea]

I though the transformer could be rewired for the different voltages around the world, if so would it not be possible to wire the machine as for a higher voltage so you get a lower voltage out or would it be too low.

[ranchak]

rogerfries, I am in no way an expert on Boss machines. I just bought one myself. I think before I bought a phase convertor I would switch to Geckos. Sooner or later you are going to have more problems with the old Boss hardware. The cost to replace your current phase convertor would have to be about the same price as Geckos, might as well move into the 21st century.

[rgrace44]

In addition to what was mentioned above, I have also changed the old bayonet fuse holder (12,13.14 and also 15,16, &17) with in-line 15amp fuse holders from Radio Shack. The old fuse holders loose there ability to hold the fuse tight and causes high current draw. This fuse change has help with numerous customer machines that I have fixed with blowing the transistors.
With the low voltage, I would check at your incoming main fuse panel. On hot summer days power companies have been known to lower voltage and this causes problems. On cool days the voltage could be normal. I would check wiring of transformers for 230 volts or 208, if wired for 230 change to 208 according to schematic.


Ray

[cloud chaser]

I purchased a board from a guy named Buck, he and his son build and test them, I had it hooked up and running in no time. The price was around $1400.
I run Mach3 and have yet to have any problems. And one thing that I was surprised about is that my stepper motors dont leave any steps anymore.
so if anyone is interested, I'll contact him and see if I can give out his phone number and/or email.