Radio cleaning and pre-emptive cap. repair?
AND NOW an annoying story from the old days. Many hears ago, I traded/ bought a "needs work" Heathkit linear RF amplifier, an SB-220. This is a fairly series piece of work, uses two big tubes (3-500Z) and runs around 3K--3300 volts on the anodes.
It runs what is called a "voltage doubler" power supply, and those must have two caps in the filter of equal value, or two banks of caps making up two equal values. The two banks are in series, so they must operate at the combined voltage of some 3200V
ANY way it was a long weekend, the amp needed new caps, and I wanted to "get on the air." So I went down to the basement "junk box" and found two military (WWII) surplus oil filled caps and put them in. I KNEW they were way under capacity rating, but thought 'worth a try.'
Months later I tore it down and installed the correct new caps. It turns out the WWII caps were SIX HUNDRED VOLTS APIECE rating!!!! In series, that's only 1200V rating working against more than 3000V!!!
Inside the box with the warning label is where the original caps mount
The original has 8 caps in series, 200uf at 450v. So 8 X 450 gives you 3600V working voltage
AND NOW an annoying story from the old days. Many hears ago, I traded/ bought a "needs work" Heathkit linear RF amplifier, an SB-220. This is a fairly series piece of work, uses two big tubes (3-500Z) and runs around 3K--3300 volts on the anodes.
It runs what is called a "voltage doubler" power supply, and those must have two caps in the filter of equal value, or two banks of caps making up two equal values. The two banks are in series, so they must operate at the combined voltage of some 3200V
ANY way it was a long weekend, the amp needed new caps, and I wanted to "get on the air." So I went down to the basement "junk box" and found two military (WWII) surplus oil filled caps and put them in. I KNEW they were way under capacity rating, but thought 'worth a try.'
Months later I tore it down and installed the correct new caps. It turns out the WWII caps were SIX HUNDRED VOLTS APIECE rating!!!! In series, that's only 1200V rating working against more than 3000V!!!
Inside the box with the warning label is where the original caps mount
The original has 8 caps in series, 200uf at 450v. So 8 X 450 gives you 3600V working voltage
