Resored Heathkit C-3

[Notimetolooz]

Originally Posted by powerking

I would bet that the Heathkit C-2/C-3 circuit design is very close to the Solar CB/CC one(s) or even copied directly (since Solar, Inc went out of business in 1945 or so). My CB-1-60 also used 2 8uF caps for the +500VDC supply in the leakage resistor divider network. I would bet that using a 250V cap to replace them is a bad idea; perhaps measure the voltage across them and make sure it not 500V! For my CB-1-60 restore, I have 2-22uF 400V caps in series with 330K-ohm (voltage balance) restistors across them. These old testers are all similar designs (not too much to a Wien bridge circuit).

Tom (PK)

Yes, I think most of these testers use very similar circuits. One replacement cap is 500V, but since the other one is the supply for the eye tube I went with a 250V. I even measured the voltage without the eye tube to see how much it would rise without the current draw on that side, turned out to be 200V if I recall. I could've/should've made them both 500V for simplicity but I went this way. The max plate voltage spec for the eye tube is 250, so if it goes higher I'll have other problems.