Hello all,
I recently picked up a non-working Mark Levinson ML-II amplifier that I am working to bring back to life. I started it up on the dim bulb tester and unfortunately there seems to be a short. Bright bulb.
I tested DC at the speakers and there was none. I tested power to the amplifier boards and there was very little, in the millivolts.
I then turned to the power supply and there seems to be my issue. Below is a screenshot of the power supply primary side circuit. I am getting full voltage from my AC mains but not at my primary connections. It seems there is a 4.7nf capacitor in that circuit that has gone bad, tests high ESR (Photo Below).
I'm wondering if this could cause my short... I'd like to replace this capacitor but I am wondering since it is on the mains side if I need a special capacitor... safety rated. I found the one below, would this work?
https://www.mouser.com/ProductDetail/KEMET/PHE450HA4470JR05?qs=PoZJcSwa6DyYJ6rxNB8hEQ==
Any help greatly appreciated, I want to be extra careful from a safety perspective on the mains side.
I recently picked up a non-working Mark Levinson ML-II amplifier that I am working to bring back to life. I started it up on the dim bulb tester and unfortunately there seems to be a short. Bright bulb.
I tested DC at the speakers and there was none. I tested power to the amplifier boards and there was very little, in the millivolts.
I then turned to the power supply and there seems to be my issue. Below is a screenshot of the power supply primary side circuit. I am getting full voltage from my AC mains but not at my primary connections. It seems there is a 4.7nf capacitor in that circuit that has gone bad, tests high ESR (Photo Below).
I'm wondering if this could cause my short... I'd like to replace this capacitor but I am wondering since it is on the mains side if I need a special capacitor... safety rated. I found the one below, would this work?
https://www.mouser.com/ProductDetail/KEMET/PHE450HA4470JR05?qs=PoZJcSwa6DyYJ6rxNB8hEQ==
Any help greatly appreciated, I want to be extra careful from a safety perspective on the mains side.
The cap link is ok.
Test cap with a multimeter for a short.
If cap is short then I would expect fuse to blow too.
Test cap with a multimeter for a short.
If cap is short then I would expect fuse to blow too.
Just checked, no short on the cap. There were no fuses when I opened it up... I've only had it on the dim bulb since then... Maybe two problems, power supply and something else. Hope it's not the transformer...
Thanks for this, very helpful. The transformer is good.Look for ac volts on secondary of transformer.
If none there then possibly transformer primary is blown.
Or maybe a short on secondary like power supply capacitors.
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