Resored Heathkit C-3

[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)

[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.

[dieseljeep]

Originally Posted by Notimetolooz

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.

Funny thing is, is that Heathkit always seemed to use parts, at that time, that were available cheap. A classic example is the use of their famous 12A6 tube. The unit shown uses a 1626, 12 volt high frequency triode with the plate and grid strapped together and used as a rectifier. They also used a power transformer with a 12 volt heater winding, to use all those war surplus tubes.