Quote:
Originally Posted by powerking
Just curious on the overhaul project; are you going to do a total re-cap, re-resistor, and re-wire job on this unit? To me, once I unsolder a component in a tester like this one's 70 year old vintage, then "it" gets replaced; even the oldy/mouldy cloth covered wiring. About the only things I kept on mine were the "hard" parts including the still V.G.C. terminal strips. To me "soft parts" include inferior/old style aged and designed caps, carbon comp & some wire wound resistors, cloth/tar wiring, rubber grommets, etc.
Tom (PK)
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Shipment of parts from Mouser scheduled for Friday arrival, so Saturday if something goes wrong.
My current plan is to replace most of the caps, (I ordered replacements for them all, but I'm going to leave the existing mica in there (C3) as it tests at 190pf with a DMM, should be 200pf.) bridge in a leg to bypass the open section (R7) of my candohm, and slap a new line cord on for evaluation purposes and then
test it. I bought a few high precision caps, basically 1, 3, and 5 on the scale (so about 25%, 50% and 75% rotation wise on the knob) of all 3 ranges and I'll see how it performs. My thoughts are that the knob might have been "calibrated" with the mica at 190pf. I plan to take the knob off and lift the dial plate out so I can remove any rust between it and the actual steel chassis it hides, but I want to ballpark it with the knob as it has been for many decades first.
I'm planning to go poke the resistors associated with the eye-tube this morning, and see if I should replace them right off too. (The 1 meg on eye tubes "usually" is way off, we'll see how mine is.)
Edit: The 10 meg is 12.17 megs (so 22% off) and surprisingly the 1 meg is 1.08 so 8% off. I'll sack them both in the first barrage...
Basically the only discrete parts I didn't order up are the R1 and R2 precision resistors. For two reasons. First: I'm not sure what the wattage needs to be. Second: I'm not intending to use the resistance functions of the unit, because a DMM can do that with orders of magnitude more accuracy and not deplete the life of my eye-tube in the process. Mine also seem to be well within 2% when I measured them so it might function within spec on the old resistors anyway.
The wiring in mine seems to be in fine condition, if it was the early rubber covered type and brittle I would probably re-weave the wires.
I picked up a tube of Simichrome at the awesome local hardware store that's over 100 years old and usually has "everything" if you look hard enough, and I'm thinking I can bring my "Goats" back to a shiny life with it. Cotton or Microfiber? I'm thinking cotton because the MF will probably just trap the Simichrome in the fibers instead of rubbing it on the corrosion...
They're coming! Soooooooon!