Need help troubleshooting Crown MA3600VZ please.
Posted 12 November 2013 - 08:04 AM
I haven't opened it yet, I wanted to inquire here for troubleshooting help first to see if this is something I can handle. I can go to him on Saturday and can perform any testing then. He was using it Stereo with the switch in the middle. He did not notice any smoke, he only smelled something more "heating up" than burning. He also mentioned that he tried to open the outer cover but when trying to turn one of the screws on the outside cover the screw would not turn and he did not want to round out the head so that's our first issue. In my experience with computers, any time a screw appears problematic I usually tap the screw this a small hammer to loosen it then attempt to unscrew it, would this same process apply here or would there be a better strategy? I am assuming that the screws on the amp were screwed in by machines which is why he cannot remove it easily?
I found this from the manual on "No Power" "The amplifier's low-voltage power supply
fuse has blown. Return amp to Crown or an authorized Crown Service Center for servicing."
I am guessing once I can get the outer cover off I can see if the fuse has blown.
Also, this from the manual for the 2400:
All 120 VAC, 60 Hz units and all Macro-Tech 2400s have a separate fuse for the low-voltage power supply and cooling fan. All units have separate fuses or breakers
for the high-voltage power supplies
Does this apply to the 3600? If so, this suggests to me that for basically any problem it would be a matter of replacing a fuse? Help?
Posted 12 November 2013 - 10:39 AM
As you mentionned the first thing is to remove the two covers (screws used are usually Torx; Probably the reason he was not capable of removing the screw. If Phillips screws are used, just turn!).
Verify the fuses, as you mention. The low voltage fuse covers the fan motor : the fanmotor is a two part device: fan motor and the low voltage supply. Though, in some newer models, you may find a stand alone transformer for the low voltage. The output of the fanmotor is 24VAC, and its load is on the main board. The output modules may use a relay instead of a fuse.
For each output board: Locate the (4) flyback diodes (diodes are reversed bias from pos rail to output rail, and another, from output rail to neg rail); Diode check the diodes : If the measurement is of the diode variety, then the output devices on that triple 'base' (base: 'B' from CBE) buss are fine; If you measure a shorted diode for instance, then you may have some leaky or defective output device(s) on that triple 'base' buss. Recommendation from Crown stipulates that 'all devices on the triple 'base' buss should be replaced with the same grade device'.
I would still advise that you contact your local authorized Crown service center.
Posted 12 November 2013 - 11:01 AM
Posted 13 November 2013 - 10:49 AM
Power down and discharge the power supply (the two same side heatsinks have the two rails (blue and red wires) connected to it. You just need to discharge via the heatsinks.). Connect one output module with two ribbon cables and power up: If all is well, the connected output side ODEP indicator should now have only the ODEP indicator lit. If not, then the connected output module has a problem. Verify voltages. Probably no rail voltages because of fault protection (psu channel relay not enabled). Power down, discharge both sides, remove the cables from the tested output module and connect the two other connectors onto the other module. Power up and verify indicators.
At least now, you may know what part of the amp is problematic.
Posted 14 November 2013 - 10:34 AM
What you see in the picture is the power supply section of the amp : We can see two power transformers, one for each side; The output modules are located on the other side of the transformers, where the air vents are located. On top of each output module, we have the 'bi-level switches' and capacitor banks for each channel. There are (4) screws that hold the bi-level modules; Remove the screws and you now have access to the heatsink section and power devices xcof the power modules. Each channel has the red wire attached to the positive rail while the blue wire is attached to the negative rail. There are two massive heatsinks per channel: The side with the red wire rail has the positive output devices while the side with the blue wire rail has the negative output devices. On each heatsink, the six devices are seperated into two banks of three devices that I will call HS (high side) and LS (low side). All three devices are linked to the base junction of the output devices. The six devices are 'interleaved' : Trio devices 1, 3, 5 are tied together and trio 2, 4, 6 are tied together. It is highly recommended by Crown to replace all three devices or trio if one of the devices is discoverd shorted C-B : the device has been probably stressed by the high voltage if the device had not succumbed to the short.
Posted 14 November 2013 - 11:40 AM
Trying to understand what you've written, please clarify, the no.1 are the 2 power transformers and the no.2 are the ouput modules so there are 4 pairs of them, 2 pairs on the left and 2 pairs on the right? Somehow I don't think I am correct so if those 4 pairs of black cyclindrical things are NOT the output modules but those are "capacitor banks"? If yes, then the output modules should be the flat rectangular long items which stratch from the top to bottom of the amp as shown in this image on top right and bottom left?
Posted 14 November 2013 - 01:07 PM
If you remove the 'bi-level switch' module, you will discover the (#1) output devices (transistors, output) on a thick metal plate (heatsink). This is the heat exchanger side of the output module. The 'module' per se, is the printed circuit board with components on the other side (bottom) of the amp.
Posted 14 November 2013 - 03:50 PM
They are like long rectangular boards stretching from top to bottom of the amp with heat sinks attached to them, one on the left side and the other on the right?
Posted 15 November 2013 - 11:51 AM
In the image, you're still not showing the correct side of the amplifier! The #1 arrow shows only the output transistors installed on heatsinks; This side of the amp is called the power supply section. Turn the amp upside down and remove the bottom cover to access the main and output modules! (If you went back to my first post : I did write down that you should remove the (2) covers! )
Posted 17 November 2013 - 11:19 AM
Posted 18 November 2013 - 04:49 PM
Note : All of these instructions and explanations can be used by other techs for their own repairs. This is not lost!
Apologies accepted; You couldn't know ahead of time that it could be complicated!
Have a great evening!
Posted 19 November 2013 - 07:05 AM