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Topic starter
04/05/2011 11:42 am
Hey guys, I have a problem with a mark V unit not being able to to complete the reset sequence on the Mo1 board. The res1 led on mo1 board comes on initially after power reset, but fails to go out to send the sequence to res2, thus starting the car down to reset selector. It is a fairly simple logic circuit, I have 3 inputs for power supply monitoring that are all in the required low state, just the same as a car that functions correctly. The problem is tat even though all the ttl logic circuits are in the correct state to activate the res1 timer circuit, which is a binary ripple counter, the counter will not count, and will not time out res1 led. The 5, 15, -15 are all good, 5 is at 4.98, 15 is at 15, -15 is exactly - 15. Mo1 board has been changed no luck. Any ideas?
06/05/2011 10:22 am
Did you trip the 55 switch on the governor to hold you at the floor. How is the V125 supply looking. Should read around 117 VDC and shouldn't have more than 250 mv AC on it. Are you reading voltages from supply or from back plane. What type of drive are you using? MD2,MD4 is it a CDM?
Last edited by halfpick; 05/06/11 02:24 AM.
Topic starter
13/05/2011 7:27 am
it turns out that the power supply was bad, we compared the bad car to a good running car with a scope. the 5 volt supply was 4.98 on the bad car with no ripple, the good car was 5.10 also with no ripple. the 15 volt power supplies were the same with no ripple. the only thing strange we noticed was that at the input of the master reset signal of the counter chip, which was to be a low signal to activate the counter, every few milliseconds we would get a slight spike to about 2 volts on the bad car. the good car had no spike and was working correctly. on our fluke meters, both the bad and the good car had a reading below 1vdc exact same measurement. it had something to do with the 5 volt return we are assuming. any way it is running again. the drive is an ERL.
13/05/2011 10:50 am
Wow, that voltage isn't really that bad. The voltage spike doesn't sound right. Most likely lost the tuning capacitors on the power supply. I forgot they used a geared application for those controls. Glad you found the problem.