No power up in Tektronix 485

[Visitator]

I wanted a scope, and finally took one a Tektronix 485 350 MHz 2 channels available for $ 25. No wonder, does not work. Either I'm not doing anything right. I have no probes. I can connect the drive, and restart. I hear a soft "click, from the inside. So I slide the cover, and reconnect it and press the power button. I realize two-bulb looking things in the high voltage board and is flashing on and off and on and off. So, I do not know if there's something I'm not doing well to try this or if there is really a problem. For those who have the service manual 485, I'm talking DS1668 and DS1669, described as "LAMP, GLOW: NEON, T-2, 60 to 90 volts". Anyone give me hand please?

[Yitzchak909]

I think the bulbs are there as a surge protector. Tension is too high, the fire bulbs, and the current limit is activated to prevent any damage. Maybe look for an open resistance to R1669? Tek service manuals are great if you can get one. You should explain why the bulbs are there, and about the measures that need to do to find the problem. I think the "tic-tic-tic" sound is only the dismissal bulbs.

[pddaugusto]

My quick guess is that there is something that draws too much current and active protection circuit. Page 3-11 of the guide exhibits a sampling / phase 6 +20 / 450mS which would have to click about 2 times / sec. If that is how quickly that the click is heard after that the protection kicks in. Why, that's a different quote, but must give place to start. Not happen to have an oscilloscope to test, right? A DMM will not do.

[Howitzer]

If DS1824 is flashing, the power of 115v is well up to this point before the investor-protection circuit. And that means the starting circuit (VR1831, C1829) is not reactivate investment (Q1834, Q1844) or the protection circuit prevents the inverter from the start. My guess is the latter, but that can be isolated. To do this, see the first 4 entries in Table 4-4, starting on page 4-7. Make some of the checks said.

[samar69]

It is assumed that "bounce" if you are using a digital multimeter. The right way to measure is with a digital multimeter, but with a scope of work with external trigger in TP1926. During the first 4 entries in Table 4.4, do what you can with a digital multimeter. See what you can do to borrow a scope of work. Tensions in Q1834/Q1844 may be attempts to start the inverter, so it makes no sense at this time. Tensions are supposed to double the input voltage 115v AC, or the value of the pp voltage line. Read "Circuit Line" on page paragraph 6.3 seconds. And I doubt T1960 is bad, we cannot say its bad if the problem points to the circuit before T1960. It is working (in a manner of speaking), because high voltages show attempts to start the continuous investment by the starting circuit. Something is preventing this, and the best method to determine this is through the control of TP1951 with a scope of work.

[Filiberto]

Assuming you are going to get a scope, in the meantime you can do more checks on the basis of message quoted. If a short circuit somewhere preventing the protection circuit to enable operation of the inverter, where it is most likely to be? I think your message might answer this: something on the 9V train is shorted. Realized I have not checked the line of 9v. You may want to check the voltage there, and while you're at it, see how much resistance there is between 9 and -9 lines (power).