Audio Hum on sys11 with rotten dog power supply

[beaky]

Hi guys
I just recently did a repair on a rotten dog power supply which had +12 on the +5 rail.
simple fault, it was a solder bridge across the +12 in and the +5 out.
The +5V tests at 5.01V but i have noticed a slight hum through the audio when the rotten dog p/s is connected.
when an original sys11 power supply is fitted there is no hum what so ever.
I had a poke around with my oscilloscope and if you look at the attached photos you will see the difference between the original p/s and the rotten dog p/s
the original p/s shows a perfect flat line but the rotten dog p/s shows something different.
I will get in touch with rotten dog and find out if this is normal and if it is then can the owner get a refund because having hum in the audio is just not good enough.
the voltage division is set at 0.5 volts so each line up and down represents 0.5 volts 

[48]

G'day Beaky,
I have a Rottendog PS on my Cyclone, there is a audio hum on it not sure if it is due to the PS though as the original was knackered when I got it.
Hope that is of some help.
Cheers,

[beaky]

must be the switch mode regulator that they are using

[Homepin]

must be the switch mode regulator that they are using

I am certain it is. David Gersic (Zaccaria Guru) gave me a serve for NOT using a switching design in my new display power supply (shown here http://www.homepin.com/other.html).

I explained to him that they are not always the best answer. Sometimes cheaper, simpler, run cooler BUT not the best choice under all conditions.

I have chosen the standard, simple, no special parts, easy to fix series regulator for this project.

[Caveoftreasures]

I like the new toy Andy. It was funny watching you run around the house connecting it up to everything. 

It made funny patterns when u connected it to the neighbours cat. 

[Mr Pinbologist]

must be the switch mode regulator that they are using

I am certain it is. David Gersic (Zaccaria Guru) gave me a serve for NOT using a switching design in my new display power supply (shown here http://www.homepin.com/other.html).

I explained to him that they are not always the best answer. Sometimes cheaper, simpler, run cooler BUT not the best choice under all conditions.

I have chosen the standard, simple, no special parts, easy to fix series regulator for this project.

I read this post earlier and was going to ask if it used a switching regulator. Would absolutely be the source of the noise..

[beaky]

must be the switch mode regulator that they are using

I am certain it is. David Gersic (Zaccaria Guru) gave me a serve for NOT using a switching design in my new display power supply (shown here http://www.homepin.com/other.html).

I explained to him that they are not always the best answer. Sometimes cheaper, simpler, run cooler BUT not the best choice under all conditions.

I have chosen the standard, simple, no special parts, easy to fix series regulator for this project.

I agree with you, you may need a bigger heatsink but they are easier for the average electronic repairer to fix. also the switch mode regulator I.C.s seem to come and go then when one fails it becomes hard to find an exact replacement or an equivalent. Also if the inductor fails unless you have documentation on the value of the inductor your stuffed.