Transistor curve tracer kit
ka2zev at yahoo.com
Thu Dec 22 08:19:08 CST 2005
Got another cute one.
One of the tricks to getting these Army motor controlers to work is to match the output darlingtons as a set.
There are three dual darlingtons that make up the output.
The p/n is
PRX KT524575 S19-A5 (the second gp might be a date code)
The tag goes on to read 75A at 500 V.
Might make a good output device for some of your 136khz transmitters.
Right now we 'do' this matching with a Fluke mulit meter in diode test mode.
The bear is these are not just darlingtons, there are some un detailed resistors and diodes, I can send a photo if anybody asks.
Was thinking of doing a better matching job on our new and growing collection of used working transistors with a curve tracer.
I have nill experience with these tools, but know of some techs that are better than I am who use them with good success. Guess it's time to learn.
Did a web search and found two 'curve tracer kits'.
The first is the gizmo that most of us make with a filliment transformer and some resistors. Ive got a Huntron here, but can't seem to do more than the basics.
This link will take you to a guy offering a fairly expensive kit.
Anybody have this kit?
Know the reputation of the company?
Think it's worth the effort?
Ideas and coments welcome.
In other news....
Thanks again for the EProms that project worked out well.
Been fighting with three units on a vexing problem. They give me 'over current' shutdowns after a 40 min to one hour run. Always when closed up and hot. On one unit there was some sensivitity (it would shut down) when I touched the 'ground buss' with my finger.
I got desperate and made a few changes.
Will let you know if the first test article runs for four hours w/o failure. It's 17:10 and it's been cranking since 14:20. If it's still working by 18:20 I will have beaten this trouble.
The fix required that I cheat.
Seems the case ground buss for this digital board comes from one point on the analog card that feeds it. By the time that ground get's to the far side of the digital board it's traveled almost 20 inches.
When I put the scope from the logic board ground to case ground, I got a fair amount of 'hash' for a reading.
I measued the DC difference from the case to a ground point at the far end of the digital card and it came out to about 77mV. When I measured the current, I got a reading of 12.8 mA.
So number one is cranking, number two is in the 'on deck circle', and number three is under the bench waiting for the first to pass, and the second to be put on the motor tester.
These are old units (made in 93) and oxygen has taken it's toll.
Im hoping that this beats this problem down.
I don't want to look at these anymore. I want them gone.
Mike Chisena in Kuwait
ps Enjoy the holidays. I have Saturday off, then back to the grind.
ps squared Sandy, send me your address so I can cut you a check for the parts. Mind like mush lately.
"You are, what you do, when it counts"
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