J99 high pitched sound

[Jeff]

Hi - I had a fully functioning J99 that I used for a couple of months with out issue. About a month ago I acquired some N72's and A12 and rearrange the order of pre's in the chassis. First time to use it, the J99 was sending out a high pitched sound that clipped the converter without anything plugged into the 'in', just the 'out' to the converter. I removed the power to it and decided to leave it be as I had some other N72's coming and would be taking the box apart soon enough.

After removing the J99, I inspected as closely as possible (magnifying glass from a typical soldering set up) and noticed a burn mark on the capacitor in C5. I'd gotten this module used, but obviously don't recall seeing anything wrong with it. I stuck it back in the box, and this time while plugged in the front light blinks and nothing powers up. Everything works fine without it being powered.

Any idea what's going on?

thanks and Happy Holidays and a wonderful New Year to all!

[tpryan]

Measure the resistance of C5 directly across the component leads. Measure in both directions. What do you find?

[Jeff]

Meter set to 200 Ω, C5 reads 3.0 both ways.

[tpryan]

Sounds like a short, but I would expect to see less than 3 ohms. Measure directly across C11 as well. The cap that measures lower is probably the shorted one. Try snipping just one leg of the suspect cap and see if it powers up.

[Jeff]

Snipped a leg on C5 and it powers up.

[Jeff]

Put a new cap ion C5, it's all better. Thanks a bunch and a happy and prosperous new year.

[tpryan]

Good job, I figured you didn't need to be told to try a new cap in C5.