Mesa Boogie F-50.. what is this?

[Andree88]

The original bias adjust is very conservative. You should have no problem.

Thank you Pedro Vecino can I ask last question? What happens if I remove the 2 resistors above the 6L6?

[Pedro Vecino]

Without them it will not sound. Originally has a direct connection (a bridge) between those points. They serve to measure the current flowing through the tubes and no has adverse effect. Is best left in place.

[Andree88]

Without them it will not sound. Originally has a direct connection (a bridge) between those points. They serve to measure the current flowing through the tubes and no has adverse effect. Is best left in place.

Thanks, obviously if I will remove the resistors I will connect back the track. But You have said that the 2 resistors doesn't change the bias, then I'll leave them on it thanks!

[Jazz P Bass]

Yes, the resistors have no discernible effect on the actual bias .

They are there so you can safely measure the bias current.

[Andree88]

Yes, the resistors have no discernible effect on the actual bias .

They are there so you can safely measure the bias current.

How can I measure the bias? 'Cause with my old Fender Hot Rod I had a "bias point test" (and I use the red cable - positive on it and then the black cable to the chassis).. here how can I measure the bias? I use the red cable between the 2 resistors and the black to chassis? Thanks

[The Dude]

Measure directly across each resistor to get bias for each tube. Measure across both resistors (outsides) for both tubes combined. Probe polarity is irrelevant since we are inferring current from the mv reading. It doesn't matter whether it's neg. or pos.

[Andree88]

Measure directly across each resistor to get bias for each tube. Measure across both resistors (outsides) for both tubes combined. Probe polarity is irrelevant since we are inferring current from the mv reading. It doesn't matter whether it's neg. or pos.

Thanks man.. like this?

[The Dude]

You got it. That's right. You can check each resistor separately to see how well the tubes are matched.

[Andree88]

You got it. That's right. You can check each resistor separately to see how well the tubes are matched.

Thank you man really!

[Andree88]

I'm sorry, I have another question about measuring bias.
If I try to measure it on both I get this:



So what does it means 06.4? 64 mV?

If I try on one I get this..



What means 165.8??

Thanks!

[frus]

I'm sorry, I have another question about measuring bias.
If I try to measure it on both I get this:

but isn't the "middle" (where they are connected to each other) also connected to the ground?
in that case, the second picture shows that the current through one tube is 16.5 mA (165 mV over 10 ohms),
whereas the first measurement is just the difference between the two tubes (0.64 mA).

[Andree88]

but isn't the "middle" (where they are connected to each other) also connected to the ground?
in that case, the second picture shows that the current through one tube is 16.5 mA (165 mV over 10 ohms),
whereas the first measurement is just the difference between the two tubes (0.64 mA).

I don't know if is connected to ground, here's the original path..they have 2 resistors only above the original path..

[frus]

if the voltage from that point to chassis is around 0V then it probably is...