Quote:
Originally Posted by Electronic M
I just use the peaking coils off digikey that Nick Miniman82 recommended many years ago. Such as this (this is one of several from that list): https://www.digikey.com/en/products/...-223-rc/969835
I've heard those coils criticized by more than one person, but the people doing the criticism don't site modern off the shelf parts as being part of their better solution...I don't have time to hunt out of production borderline unobtainium, I also don't have the equipment or skills to rewind much less wind new multi-layer coils or properly characterize them or verify performance outside of eyeballing the screen (I also don't have money or time to pick that up)...So until someone comes up with a better list of current production off the shelf parts I can buy off mouser or digikey I'm going to stick with what I know works decently in both of my sets and very soon a set I'm restoring for a customer. |
Just to let you know how I wound my peaking coils, I used a 1megohm 1watt resistor to wind the coil on. Cut out with scissors two cardboard disc from old business cards and slipped them over the resistor to hold the windings in place. Roughly calculated the number of turns to achieve needed inductance from an on line calculator (I Googled). Bought off Amazon appropriate gauge wire small spool. Made a spool holder from a coat hanger wire C clamped to a table. Fit the end of the resistor I was using to wind the coil in my variable speed power drill. Slowly (5 turns a second) ran the drill. (There was typically around 600 turns for a 1 mH peaking coils so winding that did not take too long).
When wound, I would apply the nail lacquer I bought at Walmart to hold the windings in place. I would then take the coil and measure the inductance using a series resistor, signal generator and oscilloscope to determine the 0.707 point when the inductive reactance equals the resistance. I would tend to be a bit generous with overwinding so that I could remove turns to hit my target inductance.
I did this for almost all of the 8 or so open peaking coils in my CT100. The coils in the I and Q chroma path were fairly critical in order to get a nice flat 1MHz response for the I channel and 500kHz for the Q channel. I frequency swept the luminance and chrominance channels and they matched closely the RCA published curves. And the net result was a an extremely nice sharp picture, free from ringing.
Looking at my bunch wound coils, it would be difficult to distinguish from a new commercial replacement. And my coils looked a heck of a lot better than the original ugly white blobs.