screen resistors

C

ClintN667

Well-known member
hey I have a stupid question but I feel like I should ask for my piece of mind. Does it matter how you connect a screen resistor to the pin on the tube socket?

For example the Belton 8 pin socket's pins have two holes does it matter how I feed the lead from the screen resistor? I have been putting the resistors at the top with one of the transformer leads at the bottom of pin 6.

| pin 4 pin 6 |
| | | |
---screen resistor------ -
| | |
| | OT primary
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

One of my current builds is acting a little off and I have the OT lead on the top hole then the resistor then the tube

| pin 4 pin 6 |
| | OT Primary
| |
---screen resistor--------
| | | |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||


Does it matter ? Or will that definitely cause problems?
 
It doesn’t matter. I like to hook the lead through the bottom and back through the top for a good solid connection. I don’t weave it to make it impossible to remove, but create a hook. The problem you’re discussing is somewhere else as the connection here is not the issue. As long as you have a solid solder joint and not a cold solder joint, you’re good.
 
ClintN667 said:
hey I have a stupid question but I feel like I should ask for my piece of mind. Does it matter how you connect a screen resistor to the pin on the tube socket?

For example the Belton 8 pin socket's pins have two holes does it matter how I feed the lead from the screen resistor? I have been putting the resistors at the top with one of the transformer leads at the bottom of pin 6.

| pin 4 pin 6 |
| | | |
---screen resistor------ -
| | |
| | OT primary
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

One of my current builds is acting a little off and I have the OT lead on the top hole then the resistor then the tube

| pin 4 pin 6 |
| | OT Primary
| |
---screen resistor--------
| | | |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||


Does it matter ? Or will that definitely cause problems?
Click to expand...
What amp is this? If it’s a traditional EL34, the screen are wired between 4 and 6 the OT primaries go to pins 3.

 
scottosan said:
What amp is this? If it’s a traditional EL34, the screen are wired between 4 and 6 the OT primaries go to pins 3.

Click to expand...
Yeah I wrote this up wrong. I was doing it from memory.. I should have been sitting at my desk at home in front of the amp instead of doing this from work. Basically it was the connection from Pin 6 I had the lead coming from the board with the resistor between it.
 
ClintN667 said:
Yeah I wrote this up wrong. I was doing it from memory.. I should have been sitting at my desk at home in front of the amp instead of doing this from work. Basically it was the connection from Pin 6 I had the lead coming from the board with the resistor between it.
Click to expand...
Friedman board mounts these, as long as the resistor is between the B+ and pin 4, you’re good
 
Last edited:
My tube kept red plating and I was killing myself trying to figure it out. I spent way too much time then it was the tube itself that was bad
 
ClintN667 said:
My tube kept red plating and I was killing myself trying to figure it out. I spent way too much time then it was the tube itself that was bad
Click to expand...
I just fixed a somewhat similar problem today, except it was the screen resistor itself.

The amp always made a soft frittering sound when powered up. Came on 2-5 sec after stby sw on, lasted about 10 sec, then went away. Amp worked fine otherwise. I guess it could have remained that way indefinitely, but it became a distraction even though it caused no harm I was aware of.

To make a long boring story short, the problem was first isolated by one-by-one removing every single preamp tube. The noise prevailed with the power tubes, but it was not either tube, nor HT power. That only left the grids. Making the next long part of the story short, freezing the control grid resistor with freon/fluorocarbon type cold spray, the noise really increased and always recovered when the resistor returned to operating temp. Duplicated this exactly 5 times.

Changed both 1K ohm 5W control grid resistors.

Viola!!

Problem solved. Amp is quieter now than anytime I've had it.

Sometimes even a blind hog finds an acorn!!

MrL2qnAl.jpg
 
congrats! I love building amps but its rare that I can fire up a completed build and be finished with it working 100%. Thankfully each mistake makes me learn a ton of new stuff.
 
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