Mike Bullock

Thanks again - much appreciated. Mike

Only when I bring the lamps up. I already changed that cap, so must be something else....? Thanks again - I appreciate your help with this

Thanks again, OK, so I have now done the following: Measured the voltage across both the 12v control board output, and the 28v lamp outputs - both are correct. Disconnected the 12v supply (only) and replaced with a 12v bench supply - squealing continues Disconnected BOTH supplies and replaced with separate bench supplies - squealing stops Disconnected the 28v supply (only) and replaced with bench supply - squealing stops So it would seem that it's the 28v output which is generating the squealing - not the control board Any ideas? Cheers, Mike

Hi Kevin, I was just having another look at this - not sure if this means anything, BUT the 12v output of the existing power supply is used to power the digital LED display section of the lights: just out of interest I disconnected this and the lights came on full power (i.e. bright white) with NO high pitched squealing (but obviously I had no way of controlling the lights). So my worry is that the fault may not be with the power supply - as soon as I reconnect the supply to the control panel, the squealing starts again. Or am I putting 2 & 2 together and coming up with 5....? Many Thanks, Mike

Cheers, I have sent my email address to you. Many Thanks, Mike

Thanks again - when you say 'wash', what did you use and what method?. Cheers, Mike

Hi Kevin, I have established that the issue is with the preamp, as the rumbling stops when I disconnect it (see message above from DrV). I wouldn't know how to fault find this - I am competent at de-soldering and re-soldering if I know which component is at fault, but that's about it. Having disconnected and reconnected the preamp, I notice the rumbling is considerably quieter, but still there. Hi Bryson, I checked and re-soldered these - problem still there. Thanks, Mike

Hi DrV - thanks for this: I disconnected J1 as you suggested and the rumbling stopped. Bryson suggested looking at the input solder joints, which I will now do - any other ideas spring to mind?. Many Thanks, Mike

Apologies, I have been ill since creating this post - I will look at the responses soon

Wondering if anyone can help, or has had similar issues with this unit: Mackie SRM 1801 powered sub - when I power it up, it emits a loud rumbling sound (like thunder!), even with nothing connected to the input. Anyone had or heard of this issue and, if so, how did you resolve it?. Many Thanks 🙂

Thanks Jamie - I will try replacing the cap and if that doesn't work I will be in touch.

I double-checked - yes they are

Yes, a very old repair which I had forgotten about (I've had the unit for around 10 years now!) - one of the DMX connectors was damaged and I couldn't find a replacement of the correct size to mount on the board.

Thanks for that - I'll take a look 🙂

It's REALLY loud - i.e. I just about get away with using it in my rock band, but wouldn't even try to use it with my acoustic setup.....