MT15 Help!!!

[CandidPicker]

You are very close in your understanding. There are 5 elements in a typical output tube (thus the name Pentode). 1) Plate, 2) Suppressor grid, 3) Screen grid, 4) Control grid, 5) Cathode. This drawing is a schematic representation of a Pentode 6L6 output tube. The high voltage power supplies are connected to the tubes, the highest voltage to the Plate, and a slightly lower voltage to the screen grid, the screen grid resistor (SGR) is used to lower the voltage to that grid. If the tube fails, it can sometimes take out the SGR, and if the SGR fails, the replacement tube will not function properly. Contrary to popular belief, the SGR is not designed to protect the amp in any way. Many modern amp designs have added HT fuses specifically for protection in case of an output tube failure.

As pointed out, we are speculating based on what the OP posted. I would also like to know why the output tubes were suspect.

Thank you! Now when my amp tech speaks tech language, at least I won't feel as badly when it goes in one ear and gets wedged in among other jargon.

Must also ask, how do you read a resistor's value? What color coding says what, please?

 

[veinbuster]

Thank you! Now when my amp tech speaks tech language, at least I won't feel as badly when it goes in one ear and gets wedged in among other jargon.

Must also ask, how do you read a resistor's value? What color coding says what, please?

https://www.digikey.ca/en/resources...version-calculator-resistor-color-code-4-band

 

[shimmilou]

I just remember a little saying taught to me many years ago. Bad Boys Rape Our Young Girls, But Violet Gives Willingly. Start with zero for the first letter, remembering it is black, and count up to nine.

Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Gray - 8
White - 9

After you check resistors for about 30 years, you can recognize the values almost instantly without referring to the chart.

 

[veinbuster]

I just remember a little saying taught to me many years ago. Bad Boys Rape Our Young Girls, But Violet Gives Willingly. Start with zero for the first letter, remembering it is black, and count up to nine.

Black - 0
Brown - 1
Red - 2
Orange - 3
Yellow - 4
Green - 5
Blue - 6
Violet - 7
Gray - 8
White - 9

After you check resistors for about 30 years, you can recognize the values almost instantly without referring to the chart.

Hard to believe they taught that memory aid in school. Times have changed.

 

[shimmilou]

Lol, and I cleaned it up a little, the first word used to be something other than “bad”.

 

[veinbuster]

Lol, and I cleaned it up a little, the first word used to be something other than “bad”.

Yes, I remember. It did make it easier to remember which colour was which though.

 

[Alnus Rubra]

Is that like the rainbow ?

Richard
Of
York
Gave
Birth
In
Vain

 

[shimmilou]

Rainbow?

Wouldn’t that be:

Lisa
Gave
Birth
Twice
Quickly

 

[alantig]

Rainbow?

Wouldn’t that be:

Lisa
Gave
Birth
Twice
Quickly

Filled with pride?