I'm working on my kit now and I have a few questions. I looked around and didn't see them asked previously so if I'm repeating previously answered questions I apologize in advance.

1) I have a 100mV panel meter lying around (I think it is the same as this one: partsconnexion.com/collections/meters-analog-panel/products/connex-panel-meter-1
00ma-analog-meter-round-bezel-front-mount ) that I'd like to add to my build. My understanding is that the meter should be placed in series with the 150ohm/5W resistor at the ground leg of the resistor so that the meter (-) pin faces the ground. Using my multimeter I measured the resistance of the meter and found it to be 1ohm. Since the tolerance of a 150ohm part with a tolerance of 1% is +/-1.5 ohms is is worth it to try to correct for the addition of the meter or is being within the tolerance of the part sufficient (no correction needed)?

2) in the 2019 schematic one of the optional mods was the addition of a 0.1uf/600V cap in parallel with two 220k/1/2W resistors in series, and the standard 20uf/250V caps in series in the power supply section. On the board the standard 20uf caps are side-by-side. I can't tell from looking at the board or any of the diagrams in the manual how to add the optional caps and resistors. Are the parts soldered across the cap leads towards the top of the board (the leads closest to the 6.8k and 10k resistors)?

3) Fast or slow blow 3W/250V fuse?

4) Back to the meter: I understood that the bias for the both tubes at pin 3 can be calculated by measuring the voltage drop across the 150ohm resistor and dividing by the resistance of the resistor. The 2019 schematic says to wire the meter in series with the resistor on the ground end with the (-) end of the meter facing the ground. In this location how does the meter measure the voltage drop? I would have thought (apparently incorrectly) that the meter should be in parallel with the resistor. What do I not understand?

Thanks in advance.

/d

I can't post pictures, so graphically I imagine the position of the parts in my question on the board to look like this, where polarity is marked by ():


6.8k
|
|        - R220 --- R220 -
|  ---|                              |--- |
|        - 0.1uf ------------         |
|                                           |
(+)                                       (-)
20uf                                  20uf
|                                            |
|                                            |
(-)                                        (+)
|                                             |


does this make sense? Is this correct?

Also, I'm asking about the meter since resistors in series give a resistance that is the sum of the values of the resistor. If the original part is R150 and the meter resistance is the equivalent of R1 does it make sense to try to replace the resistor with roughly R149 or is R150+R1 close enough in this application? To me this is close enough, but I'm not sure. The discussion in the other thread is about a meter with a much higher resistance.

Lastly, my question about the location of the meter is not about how to build the amp, but about how the meter functions to measure the voltage drop while located between the R150 resistor and ground. I think what I'm missing in this question is how to think about voltage drop in this location, because my first inclination would be to put the meter in parallel with the resistor and not in series.

Thanks again,

/d

That’s where I drew it. Thanks.

Next question: is there any reason to use two R220 in series instead of one R440? Is it ease of soldering?

Any thoughts on my outstanding questions is greatly appreciated.

/d

Only one? The 2019 drawing has them in series. The way I understood the drawing one cap and two resistors in series are all in parallel with the 20uf caps. Thanks

So one R220 in parallel with each 20uf and then one 0.1uf in parallel with the R220 that are in series. That makes more sense. Thanks. That answers all of my questions except for the conceptual one about the location of the meter placement. By any chance, do you have any additional insight on that? I’m looking more for the conceptual understanding than the build understanding. Thanks again.

Thanks for your help