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Since you are under the gun and while you are waiting for Mouser to deliver, why don't you fire it up without that part and check for the 16V rail?
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Experience is something you get, just after you really needed it. -
I didn't know that this would be safe to do. Since you're saying that it is, would you please tell me why? Thanks in advance.Comment
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What a sensible questionOriginally posted by lowell View Post
If you leave U18 in place with it's 16V supply pin lifted, then the gates of the IGBT's will not be driven so no harm will be done. It looks like all the safety interlocks shut down the main switcher leaving the auxiliary supply to carry on working as usual.Experience is something you get, just after you really needed it.Comment
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Ok so U18 doesn't do anything without the +16v supply. Since it will not be switching the IGBTs T2 primary will not work nor will anyting on its secondary.Comment
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I'm confused about W240 and W8A and W8B on the schematic. They are at 8 o'clock to BR1. I'm guessing W8A/B are not connected and that only W240 is. Or I am totally wrong and one or the other are used depending on the mains being either 120v or 240v. One thing I DO get is that the mains are rectified to about +/- 170vDC. Which is recified peak dc voltage for 120vAC RMS. That's about the extent of my knowledge. But I'm continuing to read about these ICs and their functions.Comment
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Exactly.Originally posted by lowell View Post
I see EL1, E120a and E240 so I think that it is these that you are asking about. For 120v, EL1 goes to EL120A and for 240V EL1 connects to E240. In the 120V position you have in effect one half wave rectifier for the top half 'PRI_HI' and another HWR that works on the opposite half cycle for the lower half i.e. PRI_LO. For 120V, the peak value of a 120v RMS input is 170V so that is what you on both PRI_HO and PRI_LO sections giving you 340V total. i.e. it's a voltage doubler for 120V. For the 240V setting it's a conventional full wave rectifier.Originally posted by lowell View Post
Experience is something you get, just after you really needed it.Comment
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Ok thanks for that explanation. So the "neutral" of the mains is between +170v and -170v on the 120v setting. So both DC rails are riding 170vDC above or below 120vAC? I'm unclear on how a voltage doubler works. Is the voltage doubled because the 2 mains secondaries are are out of phase and the neutral is going DOWN while the hot is going UP and vice versa? This seems to make sense, but correct me if I'm wrong.Comment
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The live is alternately +ve and -ve with respect o the neutral. On +ve cycles the diode conducts so that the upper caps are charged to he +ve peak value of the waveform. On -ve cycles the other diode conducts so that the lower caps are charged to the -ve peak value of the waveform.Originally posted by lowell View PostExperience is something you get, just after you really needed it.Comment
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Ok got the 2110 in there. Powered it on...nothing. +16v supply is still not there. I get +1.6v referenced to PriLo. Resistance from +16v supply to PriLo is OPEN. So there isn't something loading it down. There is no +18v supply either. T1 is NOT open on primary or secondary and is also NOT shorted from primary to secondary. I get PriHi on D60 anode.
Not sure where to look next..Comment
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Have you seen this service manual? May be a good place to start!
http://bmamps.com/Schematics/QSC/QSC...ice_Manual.pdf
even if its not the exact model # the trouble shooting is quite similar.Comment
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Specific to the problem: QSC_Power Supply Test.pdf
Thanks, Tedmich.
I had forgotten about the PLX SM.
It is very informative.Comment
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16v supply now measures 12k to PriLo. I just lifted U13 from 16v supply and the 12k is now >20k. Gotta order that IC I guess. Can I turn it on with U13 disconnected without causing harm so I can check the 16v supply?Comment
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It's a TOP210, not a 2110, I hope!Originally posted by lowell View Post
It sounds like that part is trying to work otherwise would would not even get 1.6V, so that is good
Therefore, something is loading it down. A DC resistance test doesn't reveal all - think of testing a 1.6V zener diode - it will show open until you get at least 1.6V across it. I suggest you remove all the chips that run off that rail one by one to see if one of them is the cause. You might want to use sockets when you replace them. Alternatively, you can drive the 16V rail ( with the QSV off) from a current limited DC bench supply. Slowly raise the voltage while keeping the current under 100mA and, assuming you can't get to 16V, replace the chips that get excessively warm.
I take it your client didn't turn up with a baseball bat and a couple of heavies then?Experience is something you get, just after you really needed it.Comment
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Musta had my meter on a low range. 16v supply now measures 12k to PriLo. I just lifted U13 from 16v supply and the 12k is now 27k. Gotta order that IC I guess. Can I turn it on with U13 disconnected without causing harm so I can check the 16v supply?
No baseball batt or heavies Nick haha. He must be busy or musta forgotten at this point.Comment
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Should mention there IS 5v on pin 4 of TOP210.Comment
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