B+ voltages and new lytics - Videokarma.org TV - Video

Charlie · #1 03-06-2003, 05:29 PM

When replacing electrolytics in some sets, I have noticed that B+ voltages end up being somewhat high. If the schematic calls for a B+ of 250 volts, I might end up with 300. Sometimes might even be a little higher. This amount of error usually shows up in all of the B+ sources. Never have I ended up with a B+ less than what the paperwork calls for. I have checked the AC voltages at the power transformer, and usually those are within a reasonable range of what they should be.

Would this be due to the efficiency of today's modern capacitors compared to the originals when they were new back 40 or 50 years ago? I always assumed this would be the reason for the high readings after changing lytics. Or is there another fault I should look for? Sometimes, I have considered going back and swapping out the newly installed 47mfd for a 33mfd in attempt to get the B+ closer to what it should be. I usually blow off that idea due to creating twice as much work. And then, it raises the question of whether or not the end result will be better or not? Or even a safety factor for the circuits in the set?

Comments anyone? Would love to get yall's input.

kc8adu · #2 03-09-2003, 09:13 AM

in many areas line voltage is a bit higher now than when the set was new.
if you replace seleniun rectifiers with silicon your voltages will be a bit higher too.
the primitive test gear of the day also loaded things a bit so if you use modern digital vom things will be a bit higher from the lack of loading.
i wouldnt worry about it.

Charlie · #3 03-10-2003, 04:00 PM

KC,

Thanks, I will keep this in mind. My main concern was whether or not I'd be putting stress on any components with the higher voltages. I assumed engineers had figured in a tolerable safety factor for the various components, but just wasn't sure how much I would be pushing it by having B+ voltages 20 to 25 percent higher that what the schematic called for.

Thanks again.