What resistor is this? Safe to remove?

[Mr.Death]

Would the resistor circled in red be referred to as the" grid leak resistor"?  The schematic is of a Traynor YBA3. I have done lots of mods to the preamp to make it a guitar "metal" amp(
changes not shown in schematic). I had removed the V1B treble expander circuit when I did the preamp mods to the amp because with the circuit in place it had reduced the gain dramatically. With the feedback circuit(treble expander) removed the amp had tons of gain. I recently reinstalled the treble expander and found that when I removed the 68k resistor circled in red and replaced it with a wire I got more gain. Not as much as with the circuit fully removed but close. Is it safe to have removed the resistor? Sorry for my lack of experience, still lots to learn. Thanks

[Mr.Death]

Schematic with preamp mods and feedback circuits removed.
Like this the amp had lots of gain but tone was lacking. With treble expander reinstalled the tone is fuller but the gain dramatically reduced until I remove the R4 68k resistor. I left the bass expander out of the signal as I have added the resonance and presence.

[WimWalther]

It is not a grid leak resistor, its used for signal coupling. If you remove it, you'll break the signal chain and the amp will go mute.

[Mr.Death]

I replaced with a wire. Signal passes.

[rafe]

Resistors, Part 3: Grid Leak, Grid Stopper, and the Fender Input Circuit (youtube.com)
Grid stopper. removal could cause unheard oscillations and damaging problems? .....

[Mr.Death]

Just watched the vid. Ok so the 68k grid stopper is needed. Why is it that my signal with the treble expander circuit in place is  so low, no gain? Is it because the signal is also being sent to the feedback circuit as well as the grid of the tube? Better yet how can I achieve the same amount of gain with the feedback circuit in place? I need to tweak something else because with the treble expander in place the gain is wimpy. Without its a high gain monster. Thanks

[WimWalther]

I replaced with a wire. Signal passes.

Naturally, as it should.

(You asked only about removal.. not substitution.)

[WimWalther]

Resistors, Part 3: Grid Leak, Grid Stopper, and the Fender Input Circuit (youtube.com)
Grid stopper. removal could cause unheard oscillations and damaging problems? .....

Again, R4 is not a grid leak nor (properly) a grid stop. R45 is the grid leak for V2A.

It's main function is as half of a voltage divider that cuts down the signal level from V1B.

[sluckey]

(You asked only about removal.. not substitution.)

No, in the first post he said, "when I removed the 68k resistor circled in red and replaced it with a wire I got more gain."

[sluckey]

R4 and R5 are mixing resistors.

[WimWalther]

(You asked only about removal.. not substitution.)

No, in the first post he said, "when I removed the 68k resistor circled in red and replaced it with a wire I got more gain."

He also asked if it was safe to remove - remove, not sub. It's the title of the entire thread, and that's what I was answering.

[Mr.Death]

R4 and R5 are mixing resistors.

Thanks, is it safe to remove the R4 mixing resistor and replace it with a wire to pass all the signal?

[sluckey]

R4 and R5 are mixing resistors.

Thanks, is it safe to remove the R4 mixing resistor and replace it with a wire to pass all the signal?

Yes. No harm will come to you or the amp.

[Mr.Death]

R4 and R5 are mixing resistors.

Thanks, is it safe to remove the R4 mixing resistor and replace it with a wire to pass all the signal?

Yes. No harm will come to you or the amp.

Thanks for your time and expertise.

[rafe]

Again, R4 is not a grid leak nor (properly) a grid stop. R45 is the grid leak for V2A.

It's main function is as half of a voltage divider that cuts down the signal level from V1B.



Wouldn't that be part of the grid stopper in the circuit then? I am trying to get my head around this in a basic way.

[tubeswell]

Would the resistor circled in red be referred to as the" grid leak resistor"?  The schematic is of a Traynor YBA3. I have done lots of mods to the preamp to make it a guitar "metal" amp(
changes not shown in schematic). I had removed the V1B treble expander circuit when I did the preamp mods to the amp because with the circuit in place it had reduced the gain dramatically. With the feedback circuit(treble expander) removed the amp had tons of gain. I recently reinstalled the treble expander and found that when I removed the 68k resistor circled in red and replaced it with a wire I got more gain. Not as much as with the circuit fully removed but close. Is it safe to have removed the resistor? Sorry for my lack of experience, still lots to learn. Thanks

The grid leak resistor for V2A is R45.


R4 serves as a cross between a mixing resistor and signal attenuation from the preceding stage. Removing it would increase the raw signal from V1B and reduce (but not completely remove) the effectiveness of the tone controls that feed into V2A.

[rafe]

R4 and R5 are mixing resistors.

I knew that r45 was the grid leak. I was thinking that r4 was a grid stopper. I see that you (steve) said r4 was one of two  mixing resistors. All I could find on mixing resistors was related to reverb. Is r4 not related to a grid stoper in any way? I am trying to get a better understanding of schematics and this is confusing .

[sluckey]

The simplest way to combine two signals is to use two mixing resistors. A perfect example is two input jacks feeding a grid. The 68Ks are mixing resistors. Another example is the two 220K mixing resistors that typically combine two preamp channels to feed into the PI. In this case R4 and R5 are mixing the main signal with the 'expander' signal.

A stopper is a single resistor that is in series with the grid and usually physically located very near the tube. Here's a simplified example...