Porta ministudio 07 oscillating hum that gets louder and louder

[Innesmckay]

I have recently bought an old ministudio 07 and after recording on it for the first time I noticed a humming sound on every track, like interference. The hum is sometime present as a solid background noise and other times as a oscillating one that get progressively louder until the track becomes extremely distorted and unlistenable.

Any insights would be greatly appreciated.

 

[SkywaveTDR]

Hum usually has its roots in the power supply and it filters which are very old Electrolytic capacitors at this point. It could also be broken ground solder joints but those are usually intermittent and not growing. I suspect that you have a cap that has seen better days.
Find out where the hum is with a meter or scope and then get a better grade 105* C cap from Mouser Electronics. That is how I would fix it but you need to find out which one. I just do not change all of then as then you might not find the real problem. Might even be a regulator but caps would be the first guess.

 

[Innesmckay]

Thanks, the deck was sent with an off brand power supply so I’ve order a replacement to see if that fixes the problem. If not I’ll check the caps.

 

[SkywaveTDR]

I have made my own supplies when needed. You have to watch what you put into these things as parts can get damaged fast like People do all the time with the WM-D6C Sony Walkman

 

[SkywaveTDR]

The fastest way to test a unit that uses DC power is to use a battery. Some Technicians only need to get a proper plug then learn the polarity and then hook up a proper voltage supply. If the Hum or noise persists with DC power then the problem is outside the power supply or after it if looking at the schematic. Many things can cause unstable circuits and many things can also be the result of using these so called advanced audio interfaces. Remember they are all built for profit not to make the best possible item. So sometimes you need to power the decives up and go looking for the cause. This is likely to require some test equipment and knowledge to use it.