ST70 questions: bias and hum problems

Tubes Asylum

Questions about tubes and gear that glows. FAQ

Another ST70 just arrived. As I powered it up, I noticed an annoying hum which is completely gone when the amp is plugged to any preamp. I do not have this problem with another ST70 so I wonder what is causing this.
Also, I can't bias it to 1.56v. In fact I only get 0.9v even with new tubes on both channels. Where should I look to correct this - are the 2 bias pots defective or is it the bias resistors.
Thanks for any advice.

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

Topic - ST70 questions: bias and hum problems - Francis S 06:16:21 07/28/00 (4)

Re: ST70 questions: bias and hum problems - Chris L 08:03:08 07/28/00 (2)

Re: ST70 questions: bias and hum problems - Gary Kaufman 14:25:23 07/28/00 (0)

Re: ST70 questions: bias and hum problems - Francis S 11:37:27 07/28/00 (0)

Re: ST70 questions: bias and hum problems - Gary Kaufman 06:49:42 07/28/00 (0)

You can not post to an archived thread.