How can I correctly measure capsule voltages

[kevinglis]

Im sooo late on jumpin into the royer mxl 2001 5840 mod, but better late than never, so after reading everything I could possibly find, aquiring all components new, cheap, nos, etc. and experimenting I have built 3 LDC's and 3 power supplies. I used the standard MXL 2001 body with the stock k67 and also Cad gxl2200(which are the same bodies minus the transformer shielding can). My first build worked a soon as I powerwd it up but it was all hi end harsh as hell and no low end, swapped the tube,nope,swapped the capsule,nope, swapped all rthe caps,resistors, and finally, the transformer. Yep, I did read that a transformer with a short would demonstrate those symptoms so after ordering a couple of brand new 2480's and dropping it in boom!sweet tight low end and smooth highs. I guess thats what I get for buying a 2480 off ebay with the buyers score of 2. and for that Transformer being the candidate for my very first build you can imagine the frustation, the self doubt in my work, the desoldering, resoldering , on and on, but in the long run it helped with overall understanding and improvement in my work, So they work quite nice and I am  happy with the way it sounds but... Im not an expert on the voltages and correct test points, but what is bothering me is the voltage I am getting at the capsule node after the voltage divider, Im sure it is supposed to be 60v but at the 22m and .1 cap and I am only reading 20v. so I do not know if my DMM is reading false value due to high impedance or I got something wrong in my circuit, but im telling you its all correctly populated, and it does sound quite nice, so if this is a "if it aint broke dont fix it" senerio that just wont sit well with my confidence in my future builds, No..I Need to know how to check all, so If anybody has run into this before and know what Im not doing, I would love some help. Sorry for the long entry but it is my first post. all my other voltages are as follows;
B+ 104v
heater 6,3
plate 38v
cathode .49v

 

[0dbfs]

If you can post a schematic then it will be easier to define a good spot for taking measurements.

If your meter is a 10M meter then it will act as a voltage divider when measuring in similar or higher value nodes so you can determine the actual voltage if you know what the impedance of your meter is by doing a little math with your meter in the circuit.

I used this calc:
http://www.raltron.com/cust/tools/voltage_divider.asp

And if I input 60V and 22M and solve for R2 (your meter) that it's an 11M meter. If I fill in 22M and 10M (for your meter) then I get 64V @ the capsule. Sounds like you're in the ballpark though.

Depending on the circuit you may also be able to measure at a different node to get a more accurate reading. For instance perhaps on the other side of the 22M resistor you mentioned. Then you can compare and contrast your measurement results at the different nodes to confirm what you should be seeing.

Electrometers can be used to more accurately measure voltage in higher impedance nodes.

Cheers!
-jb