Help with determining resistance.

[jhockridge]

Originally Posted by ms660

Excluding the possibility of any leakage....

….R1 to R3 (inc.) can be measured in circuit.

R4 can be measured in circuit.

R5 to R8 (inc.) can be measured in circuit if the function switch is switched to DC or Ohms.

R9 can be measured in circuit.

R10 to R16 (inc) can be measured in circuit.

R17 can be measured in circuit.

R19 to R24 (inc.) can be measured in circuit.

R30 and R32 can be measured in circuit.

R36 can be measured in circuit if the valves are removed.

R18, R28 and R31 should be measured out of circuit.

R35 and R36 would be best measured out of circuit due to the rectifier and reservoir capacitor possibly giving errors.

So far as I can make out from the schematic:

http://rhetoricity.com/misc/tubes/vt...M%20manual.pdf

Lawrence.

Is there any good sources for learning the theory that led to your conclusions, or is it just experience ? Are there any rules of thumb?

Best wishes!

[ms660]

Originally Posted by jhockridge

Is there any good sources for learning the theory that led to your conclusions, or is it just experience ? Are there any rules of thumb?

Yes, experience for me, spent lots of years looking at schematics as a trouble shooter, I was a lot faster back in the day but even now I'm not too bad at it.

Yes, just look at the schematic for that meter, the switch positions as drawn in the schematic are given and the direction of rotation is given, from that you can see if there's any parallel paths in terms of DC and if they can be avoided by selecting a different switch position.

Top tip, the current goes around and around in a circuit and all circuits contain potential dividers.

As always, learn the theory first and apply to practice, start with Ohms Law and commit to memory.

Understanding the switchery at first can seem a bit daunting in some schematics but always remember that all circuits can be broken down to smaller more understandable ones and eventually the whole picture can be worked out.

Others might have different views.

Lawrence.

[Kentode]

JH, get yourself a copy of Foundations Of Wireless by M.G.Scroggie.

It's a great book for solo learning and goes from first principles up, anything you don't get can be answered here.

Lots of worked examples to illustrate the calculation or to test if you understand.

Good luck with the restoration.

[jhockridge]

Lawrence - thank you. I have been teaching some very basic theory as part of the A level Physics scheme for the last few years. I have never really touched the practical side of things so it is a whole new world. Really enjoying learning something new ! Thanks for the tips - make a lot of sense.

[jhockridge]

Originally Posted by Kentode

JH, get yourself a copy of Foundations Of Wireless by M.G.Scroggie.

It's a great book for solo learning and goes from first principles up, anything you don't get can be answered here.

Lots of worked examples to illustrate the calculation or to test if you understand.

Good luck with the restoration.

Thankyou ! Will have a look for a copy.