post #1 of 1
Thread Starter 

So I got a Dynaco st-70 awhile ago and it worked great before i took it apart the only things I really wanted to change on it was the speaker connectors to banana plug inputs and change the front rca inputs to gold plated and further spaced apart and last but not least the replacing the Selenium rectifier with a 1n4007 diode.


When I was taking the case apart I ended up turning both bias ports thinking they were just screws while everything was unplugged so after making the changes I wanted to I attempted to rebias my amp.


Basically the results I got was that the voltage on the biaset is never more than 1v the highest is .85v and the lowest ruffly being around .20v. I have a good multimeter the Extech ex530 and tested it on a battery and got 1.6v. I'm not even sure what could have went wrong I only added an 8 ohm output being that it's what i use and i was going to figure out if i wanted the 4 or 16 ohm on the other speaker inputs later on. The not connected wires are connected the way they were before either way and with shrink tubing over them so they can't short out. the wires that are going to my 8 ohm plug are the orange wire coming off the transformer and then ground going to ground along with the black wire from the transformer.


I'm pretty sure i did that part right which then makes me think it might be the new diode but it doesn't feel hot after it's plugged in. I also switched back to the rectifier and got the same results.  I also tested the diode after i took it out and it looks good.


I have a pretty good knowledge of how electronics work but little experience.. any help would be great because i'm totally lost now at this point