Bad EL34 in ST70

151.198.2.27

Posted on September 3, 2009 at 17:03:53

Just picked up a nice modded ST70 and it worked well for a day or so until I noticed strange noises from left speaker and noticed one of the EL34's glowing bright red. Can I replace just the 1 tube or do I have to replace all 4?

Tubes should be replaced in pairs.

Bill Thomas

19:01:10 09/03/09

And/Or Match Tubes: here's an easy way

dcriner

14:56:30 09/04/09

Tubes should be replaced in pairs., posted on September 3, 2009 at 19:01:10

Bill Thomas
Industry Professional

Posts: 1330
Location: Southern USA
Joined: January 3, 2004

BUT, before you condemn the tube, swap the two EL34's in the affected channel. If the SAME tube glows red (in the DIFFERENT socket), the tube is *probably* the culprit. If the OTHER tube now glows red, you PROBABLY have a problem with either a bad coupling capacitor that is leaking, or a bad tube socket. Either way, you will have to replace the two EL34's in the affected channel. The one that was glowing "cherry red" is a goner. This means you will have to replace BOTH EL34's in the bad channel.

What tube brands are the EL34's?

Hope this helps.

Bill

And/Or Match Tubes: here's an easy way, posted on September 4, 2009 at 14:56:30
dcriner Audiophile Posts: 79 Location: Chicago area - USA Joined: September 11, 2005	Here is my quick and dirty way to match EL34 tubes in an ST-70: http://enginova.com/Tube_matching.htm Push-pull amps can benefit by matching each pair of amplifier tubes. Doug

Page processed in 0.058 seconds.

Dynaco-Doctor Forum

Bad EL34 in ST70

151.198.2.27