Home Tube DIY Asylum

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

Re: Dyna ST-70 bias

Yup, should have. You might have really leaky coupling caps.

Thinking out loud... The 0.8v that you're measuring isn't bias, but the resulting voltage drop across a 15.6 ohm resistor. With 1.56v across 15.6 ohms you are seeing a bias current of 1.56/15.6 or 100ma which is 50ma per EL34. If you're only seeing 0.8v you're only getting a current of 0.8/15.6 = or 51ma total.

You need a "less negative" bias to get more current. If you measure the voltage at pin 5 of the EL34 you should get around -32vdc.

So, measuring the voltage at pin 5 will give you some idea if you're problem is the bias voltage or something else. Also do replace the coupling caps - if they're leaky (and the almost always are) you're chasing your tail.

Good luck!





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


Follow Ups Full Thread
Follow Ups
  • Re: Dyna ST-70 bias - Gary Kaufman 01/26/0313:22:50 01/26/03 (0)


You can not post to an archived thread.