Crown xti 4000 SMPS Strange short

[milhousesmom]

Hello, I am working on a crown xti 4000. I have a strange problem. With the power cable plugged in but with the unit switched off it is drawing 0.16 amps and my lightbulb current limiter glows.

My steps taken are as follows:

Step 1: Tested fuse it is okay. I removed the a/c switch to see if that was faulty. It tested fine and with the switch out of circuit I was still getting the 0.16 amps.

Step 2: I removed K1 Relay. No Change

Step 3: I removed L1 coil to isolate the power cable from the rest of the board. Still got glowing bulb and .08 amps now.

Step 4 Removed C50 capacitor and no current and no light. I thought that was the problem. Replaced C50 and C49 with brand new ones and short retuned.


When the power cable is unplugged there is no continuity between the legs of the capacitors. With the power cord plugging in there is continuity.

Is this a normal situation?

Thanks

[redwire]

Re: Crown xti 4000 SMPS Strange short

I would say this is normal - the mains X-caps are very large at 1uF each and will have a lot of (capacitive) current flowing, around 45mA RMS each at 120VAC.

If you are repairing it, it looks like the kickstart V_KSTART voltage is one to keep an eye on if the SMPS won't start.
Be careful working around the mains filter caps- they are huge almost 4,000uF total!

[spiros.p]

Re: Crown xti 4000 SMPS Strange short

is normal. i have plugged 8 amplifiers on my rack and when i open the main swicth fuse to operate some of them i see the amp meter on the power distro drawing 500ma to 700ma with amps closed. the amps is 5 class D and the rest 3 is class H with swicthmode psu.