Hayman

Soundcraft series 600. Loud hum problem.
« on: June 21, 2005, 02:12:25 AM »
Hi,

I bought a Soundcraft series 600 console last night. The console has not been used for the last couple of years.

When I checked it at the sellers house, it worked fine. When I powered it up in my studio it worked fine.........for 20 minutes. Then something happened. A pretty nasty and loud sound came out my monitors, and then there was just a loud hum coming from the console mixbus-outputs.

I checked the line ouputs from the channelstrips and they seem to be fine. All the mixbus-outputs have the same hum (mix, c-room, stodio and headphones).

After a while the music came back through the mixbus but the hum is still there.


Anyone have a idea of what the problem could be?

Thanks in advance.


Richard


Hayman

Soundcraft series 600. Loud hum problem.
« Reply #1 on: June 21, 2005, 02:56:40 AM »
Quote from: "Viitalahde"
I'd say it's the caps in the power supply.. Sounds a lot like it to me.



That's what Jacob suggested too. There are 4700uf/50v caps on the +17v and -17v lines. I guess I can replace them with 63v caps (that's what I find in my Farnell catalog)?

Any particular brand/type I should use?


Thanks

Richard

gyraf

Soundcraft series 600. Loud hum problem.
« Reply #2 on: June 21, 2005, 03:43:56 AM »
Richard,

First check how your power supply lines are doing (under load). Dc voltage and AC component. Check phantom and auxiliary led/light voltage as well.

This will tell you how things are, and what is needed.

Hum could also come from one channel shorting/loading the PSU to a bit over it's limit.

the 4700u/63V electrolytics will work fine - though I'd prefer 10.000u/50V there.

Jakob E.
..note to self: don't let Harman run your company..

Soundcraft series 600. Loud hum problem.
« Reply #3 on: June 21, 2005, 09:06:16 AM »
Also, the big caps in some Soundcraft power supplies are twist-lock, and they can come loose when the PS is moved. Check to make sure they're in tight.

 :thumb:
Seth

The definition of insanity: "Hey, this thing could be really cool - if I had the money to fix it up, which I don't, but if I did it could be really cool - if I had the time, which I don't, but

bcarso

Soundcraft series 600. Loud hum problem.
« Reply #4 on: June 21, 2005, 09:27:55 AM »
Wiggle everything, especially any connectors.  Does the hum go away for a while when you cycle the power?  Sometimes this mimics the behavior of marginal 'lytics but is in fact often the transient breaking through corrosion somewhere and re-establishing a contact for a while.

OTOH it may well be the PS caps as described.

Svart

Soundcraft series 600. Loud hum problem.
« Reply #5 on: June 21, 2005, 09:39:20 AM »
PS caps maybe, but everyone overlooked the fact that he stated that the channel line outs are fine.

"I checked the line ouputs from the channelstrips and they seem to be fine. All the mixbus-outputs have the same hum (mix, c-room, stodio and headphones)."

this console has removable channels correct?  i would remove the buss channels from the console and see if the main outs still have the hum.  replace each buss channel until you get the hum.  if it is only one buss channel then just trace it with a scope until you find the problem.  if you still have hum with only the master channels, then the summing from the buss channels might be screwy.  if this console sat for any length of time I would expect the caps to have dried and then died when juiced.

or you could do the shotgun approach since caps in channels going bad also shows the need for the PSU caps to be replaced too.

Good luck.
Welcome to the GroupDIY leper colony! when something falls off, we just replace it with a tube!
occupation: General Electron Mayhem

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Hayman

Soundcraft series 600. Loud hum problem.
« Reply #6 on: July 01, 2005, 05:59:00 PM »
Thanks guys,

Replaced the three 4700uf/50v caps with 6800uf/50v's. The hum is gone and the sound is back. :grin:

Thanks again.


Richard

Peter Simonsen

Soundcraft series 600. Loud hum problem.
« Reply #7 on: July 02, 2005, 03:22:39 AM »
Quote from: "Hayman"
Thanks guys,

Replaced the three 4700uf/50v caps with 6800uf/50v's. The hum is gone and the sound is back. :grin:

Thanks again.


Richard


this just reminds me how crazy the world of electronics are !!!  :green:  Glad it worked out for you..*S*

Kind regards

Peter


 

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