Ralph Mowery wrote:



I am restoring a Eico VTVM model 221. The DC requires a test lead with
shielded wire and a 15M resistor in the probe. It did not come with the
leads. I have all the connectors and the resistor, but need shielded
cord. Can I just cut the ends off a guitar cable to make one?


** Probably be fine ,just cut one end off though -
the 1/4 inch plug is needed !!!


I will use this meter for tube radios in the RF and IF stages, so I do
need the shield.


** DMMs don't come with shielded leads, only scopes do.


You missed the part where it is a VTVM, not a DMM.


** I was particularly interested in the fact the Eico is a VTVM.


The old VTVMs I have seen often have a shielded probe.

** Mainly because they are such wide band meters, covering the range up to several MHz. Most only have one input connector, a coaxial type, switched between DC and AC use.

However, the Eico has a separate DC voltage jack and that is the one the OP asked about.

Modern DMMs have similar input impedances to VTVMs ( like 10 or 11 Mohms) and full scale DC ranges starting from 2V rms.

So very comparable.



...... Phil