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Crown 5000VZ help!


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#1 hoanglucky

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Posted 24 July 2013 - 08:02 PM

I' ve a crown 5000VZ, but it 's damage 2 channel, when I 've removed all output transistor, I check all pre driver, driver transistor. it's OK. I check all resistor in module output, it's ok. I install module channel 1 to test voltage Vbe of driver ( I 've removed all output transistor, only driver transistor) but R520 and R521 is burnt. Vcc is not balance. Anyone had repaired a Crown 5000VZ, Please help me resolve that problem. How to check voltage driver transistor to install ouput transistor. I repair some Macrotech Crown( 800,1200,3600), normal I check voltage the leg E of driver before install the output transistors, it 's about - 0.55V. Crown 5000VZ is the same?

#2 joust

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Posted 29 July 2013 - 02:46 PM

If you have a fault with one channel, you won't get appropriate VCC unless all shorts are removed.
In this case, you did remove all power devices and discovered two burnt resistors, an 8,2 ohms and 22 ohms. These should be replaced and the predrivers tested. If you find no shorted devices, install new PNP and NPN devics. This should do the trick. I rarely had a unit that didn't work when this was done. Also, verify the ,33 ohms WW power resistors. I've found, though rarely, open resitors.
Go module by module; You don't mention if the other module is workable. If it is in working condition, just swap modules to test your repair.
Also, verify the bi-level switch: you may find some shorted, or even blown rail switchers (fets).

Good luck!

Alain

#3 hoanglucky

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Posted 01 August 2013 - 09:26 AM

Thank for your support!
2 modules is the same, if I remove 2 resistor 8.2 ohm, 22ohm, Vcc is balance, Vcc is about +/-35V. when I sold 2 resistor again, it burt again, When I install 4 transistors output( 2 for low side, 2 for high side), sometime it start ok, sometime it start failure, DId you  ever checked Vbe of driver transistors when you didn't install output transistor? I think if the circuit is normal, two resistors isn't burnt! are'nt you?

#4 joust

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Posted 01 August 2013 - 10:24 AM

I do agree that the resistors should not have burned [again]. So you may have another faulty transistor(s) upstream to the resistors. Check for C-E shorts or low impedance on all drivers and low power transistors. Don't forget about the two in the heatsink! Note: The third device in the heatsink is the thermal sensor.
There may be instances when the IC is not powered correctly: the +15 or the -15 doesn't reach the IC! Verify edges of cards: sometimes, if using fog machines, the printed circuit lines may corrode and open.
Did you find any of the output devices shorted? If so, replace with genuine (and graded) Crown parts (highly recommended).

Alain