Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Return to Tube DIY Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Loud squealing noise in new project

142.119.47.168
Posted on September 27, 2020 at 15:33:14
vetmedrobert@gmail.com
Audiophile

Posts: 453
Location: Ontario
Joined: September 20, 2007



I just finished a 45 circuit closely based on Ale Moglia's 7193/45 schematic. Plate and cathode voltages measure very close to the desired voltages in both channels, with a dummy load and inputs shorted. When I connect speakers and a source with volume off and switch on power I get a series of pops then a loud squeal. It seems to be in the left channel but as I am standing quite close to the left speaker in order to be able to power off rapidly, I would not swear by it. At this stage I am rather reluctant to switch it for fear of damaging something. Any ideas on diagnostic steps to take would be greatly appreciated.

 

Hide full thread outline!
    ...
RE: Loud squealing noise in new project, posted on September 27, 2020 at 18:13:04
Chip647
Audiophile

Posts: 2645
Location: The South
Joined: December 24, 2012
 You obviously have an oscillation and a ton of places it could pop up. Ground the input and take out the output tube. Use a meter to look for AC voltage representing the noise where it should not be. IF you cant find it with the output tube out, put it back in and use a high power resistor on the output rather than a speaker and find the AC.

 

RE: Loud squealing noise in new project, posted on September 27, 2020 at 19:45:58
vetmedrobert@gmail.com
Audiophile

Posts: 453
Location: Ontario
Joined: September 20, 2007
 Well, actually while waiting to see what sort of advice I might get I resorted to wetting every solder connection. You know, the advice I have been given in the past that never solved the problem:) I also cleaned the sockets at the same time. And its working fine now! I'm using a Heyboer power transformer a Magnequest clone and its not even warm after 2 hours playing. Really pleased, thanks for responding.

 

No, not a bad solder connection, What I meant was that you are using a lot of solid state, posted on September 28, 2020 at 15:54:30
Chip647
Audiophile

Posts: 2645
Location: The South
Joined: December 24, 2012
 Solid state devices can oscillate. Look at where you should have carbon comp resistors (suppressors) very close to the transistors and look at the lengths of your connecting wire. The oscillation is coming from one of the active elements. It should be easy to find if you have a meter.

 

Page processed in 0.022 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]