So I was adjusting my bias today and apparently I had shaky hands. The temps were around 44c and I wanted to bring them up to 50-52 which I did.
In the process of measuring, I touched the bottom lead of one of the resisters to a ground contact which made a nice spark. I have to say, it was a high quality spark. I used to weld so I was impressed. Part of the ground pad under a nut is MIA though.
After adjusting the bias and almost lighting the house on fire the amp sounds really nice!! It is amazing how durable these things are.
Should I have any concern now that I have done this?
This brings me to the DIY portion of this post. I meguivered these fancy screw drivers because the bias pots are hard to access. After some more research and development I realized that I should add an electrical insulator so I shrinkwrapped my creation.
The steel is very hard and brittle so I heated it until it was red hot with a torch and hammered the tip to a 90 degree angle with my hammer. I then ground the tip with my bench grinder to form a flat head screw driver tip. I may make some more at other angles. Took all of 10 minutes to do both. I may make some more.
I didn't know if anyone has made screw drivers like this for adjusting bias on these S series amps so I wanted to share.
In the process of measuring, I touched the bottom lead of one of the resisters to a ground contact which made a nice spark. I have to say, it was a high quality spark. I used to weld so I was impressed. Part of the ground pad under a nut is MIA though.
After adjusting the bias and almost lighting the house on fire the amp sounds really nice!! It is amazing how durable these things are.
Should I have any concern now that I have done this?
This brings me to the DIY portion of this post. I meguivered these fancy screw drivers because the bias pots are hard to access. After some more research and development I realized that I should add an electrical insulator so I shrinkwrapped my creation.
The steel is very hard and brittle so I heated it until it was red hot with a torch and hammered the tip to a 90 degree angle with my hammer. I then ground the tip with my bench grinder to form a flat head screw driver tip. I may make some more at other angles. Took all of 10 minutes to do both. I may make some more.
I didn't know if anyone has made screw drivers like this for adjusting bias on these S series amps so I wanted to share.
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Quote--- " I touched the bottom lead of one of the resistors to a ground contact which made a nice spark " , have you checked the value of the resistor to see if its still the same ?
right-angle screwdrivers | McMaster-Carr
right-angle screwdrivers | McMaster-Carr
I will check the resister. Thanks for the suggestion.
I know about right angle screw drivers. I tried one that I have and it was to large to fit in that space also not long enough.
It scares the crap out of me when I do that. Or discharge a cap. Even small ones pack a nice spark and makes the wife check that my life insurance is paid up!
enthusiasm smileys
Is this the spot where you are supposed to measure the temperature? I am measuring it right on the head of the screw. I have heard multiple things all of which give a variety of different temperatures.
Last one I read was put your hands at the top of the heatsinks which is about a 7 degree Celsius difference. if that is the case, I really need to raise my bias quite a bit.
Thanks!
I agree. That is why I made the heat shrink screwdriver, that way I don't have to worry about it. I was good at doctor when I was a kit but many years have gone by...
I do it on the top base surface of the heat sink. It's just a convenient spot, and
shouldn't be all that different from the rest of the base. Also, you want to read
the black surfaces with the IR thermometers.
shouldn't be all that different from the rest of the base. Also, you want to read
the black surfaces with the IR thermometers.
Okay thanks. I figured out why the temp was so different. With my A/C on, one of the registers on the ceiling was blowing on the amp which accounted for the temp difference. Without that the temps are only about 1 degree different.
I plan on building one of your amps after I mow through some other projects that I am doing. Thank you for making all of this available to us.
I plan on building one of your amps after I mow through some other projects that I am doing. Thank you for making all of this available to us.