Another KCS47 Restore...No High Voltage/B+ Down 25V

[Chris K]

Before the first power up I did a dim bulb series to make it safe. When I got no high voltage I replaced the 3 electrolytic cans with 4 section adapt-a-caps and a few but not all the caps in the power, horizontal and vertical sections. It’s interesting there are so many opinions on this process. Bob has commented here replacing all the caps is the prudent thing to do but I’ve watched restoration videos of his where he baselines an untouched chassis from this era using a gradual power up with his Sencore isolation transformer Variac. Shango usually does the same although his videos are more resurrections than restorations and he has no fear of the magic smoke. I don’t do a power slam at 120V without replacing the cans first because I have seen videos where a short can take out a transformer so I don’t want to risk that. Are you saying I should replace everything or just the cans and all waxies in the 3 main power sections I've been working on? Is leaving the RF and IF caps alone until I get HV and a full deflection raster an ok thing to do or am I still asking for trouble with a shorted cap in the video and sound signal sections? To be honest, I usually have done complete recaps prior to first power up but from what I’ve watched that’s not SOP. Gradually replace the paper and foil caps and check function often before proceeding is the smarter more conservative approach. That’s what I surmised anyway.

[Kevin Kuehn]

Originally Posted by Chris K

Before the first power up I did a dim bulb series to make it safe. When I got no high voltage I replaced the 3 electrolytic cans with 4 section adapt-a-caps and a few but not all the caps in the power, horizontal and vertical sections. It’s interesting there are so many opinions on this process. Bob has commented here replacing all the caps is the prudent thing to do but I’ve watched restoration videos of his where he baselines an untouched chassis from this era using a gradual power up with his Sencore isolation transformer Variac. Shango usually does the same although his videos are more resurrections than restorations and he has no fear of the magic smoke. I don’t do a power slam at 120V without replacing the cans first because I have seen videos where a short can take out a transformer so I don’t want to risk that. Are you saying I should replace everything or just the cans and all waxies in the 3 main power sections I've been working on? Is leaving the RF and IF caps alone until I get HV and a full deflection raster an ok thing to do or am I still asking for trouble with a shorted cap in the video and sound signal sections? To be honest, I usually have done complete recaps prior to first power up but from what I’ve watched that’s not SOP. Gradually replace the paper and foil caps and check function often before proceeding is the smarter more conservative approach. That’s what I surmised anyway.

No you don't want to replace ceramic caps in the RF and IF unless you later identify a known issue with one. Keep in mind some of the individuals you watch videos of have a vast experience with how these circuits work and lots of doing under their belt. Shango in particular does things different just to go against the grain. Don't me wrong, he's a brilliant technician, but he's also intentionally adding drama for the sake of viewer engagement. I get his humor, so I'm not offended by any of it.

[Kevin Kuehn]

ESR isn't very useful when it comes to testing paper or film caps. That's primarily useful for finding high resistance or open small electrolytics while they are still in circuit. Completely different than leakage. Although if C156 had high ESR it's probably bad just the same.