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Post by mastertech on Jun 21, 2022 11:11:03 GMT -5
Well, assuming you properly tested ic701 out of circuit then it appears to be faulty. However, I would not think that would cause the other problem reading you are getting. But there are more ways to test that power supply in and out of the unit and with that regulator removed to see if things are functioning correctly before ordering and replacing new parts.
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 21, 2022 22:58:36 GMT -5
Well, assuming you properly tested ic701 out of circuit then it appears to be faulty. However, I would not think that would cause the other problem reading you are getting. But there are more ways to test that power supply in and out of the unit and with that regulator removed to see if things are functioning correctly before ordering and replacing new parts. Never thought of it that way really. I will try to start it up without the IC701. It is a 7805A regulator. |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 28, 2022 21:11:19 GMT -5
Well, assuming you properly tested ic701 out of circuit then it appears to be faulty. However, I would not think that would cause the other problem reading you are getting. But there are more ways to test that power supply in and out of the unit and with that regulator removed to see if things are functioning correctly before ordering and replacing new parts. Been out for awhile had to deal with other things. Went to the local shop this morning and just right out bought a L7805CV instead of a 7805A which is what is only locally available. Assembled everything and tried turning on. No deal. No response or anything. Tested the newly placed regulator, didn't give anything, removed from circuit and tested it. It got busted/burned. Was pretty sure it was working before I inserted to the circuit. Testing method was pretty straight forward. Pin 1 - 12V pin 2- common, tester red on pin 3 and black on pin 2. It was 5V back then. After inserting, now it's just mV and regular is very hot to the touch. Makes me think something has shorted it out. Removed all connections to the minipower supply except the 120V mains, and with the IC701 - regulator removed turned it on. The blanked pins doesn't even get a 12V. Makes me think I am missing something, what could have burned the regulator? Also, the minitransformer is a bit hot, can be touched but warm to the touch and warmer/hotter than normal compared to before. Also, Transistor TR703 gets very hot and can't even hold it very long as it gets hot. Anywhere I should go from here? Unit is toast? update: Yup, TR703 is pretty toast too. Junction is now at 0.28V B-E, B-C, even at reversed polarity. Since before I do have some crazy -86V on the collector of TR703, this is with or without the TR703 removed from circuit. Manual says I only should have -33.6V there. mastertech |
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