Sound Skulptor forums

Build help and troubleshooting => MP566 Tube microphone preamplifier => Topic started by: MRMNW on May 18, 2026, 08:37:45 AM

Title: 5.66 Problems
Post by: MRMNW on May 18, 2026, 08:37:45 AM

Hi, 
built this a month ago and it has worked fine,
Now when switching the chassis on it clicks on and off before eventually working after switching it off and on again.
There is also a very low and thin sound. I think it may have overheated. 
Any help much appreciated.
Thanks

Title: Re: 5.66 Problems
Post by: JPK on May 19, 2026, 04:14:54 PM

Can you do the high and low votages check in the test guide, steps 3 and 4?

Title: Re: 5.66 Problems
Post by: MRMNW on May 20, 2026, 01:56:41 PM

I get 222v and -5v

Title: Re: 5.66 Problems
Post by: JPK on May 20, 2026, 05:47:34 PM

The voltages are OK.
Check that the 2 voltages are sequenced and come up after a few seconds.
Check that it is not the chassis that is loaded too much. What brand is it? Did you add more modules recently?

Title: Re: 5.66 Problems
Post by: MRMNW on May 20, 2026, 05:57:34 PM

Thanks, what do you mean by sequenced?

It's one of your 501 Chassis, but does the same in my API lunchbox too.

Title: Re: 5.66 Problems
Post by: JPK on May 21, 2026, 04:29:03 PM

what do you mean by sequenced?
When you turn on power, the high voltage comes up after 2-3 seconds and the heater voltage after 5-6 seconds.

Check that you don't have any DC voltage on TP4.
Try to follow the signal: https://www.soundskulptor.com/forum/index.php?topic=209.msg981#msg981