Quote:
Originally Posted by JohnCT
Yes, but if one turn shorts out to an adjacent turn, it will have no measurable effect on the resistance you read with a meter. But what happens with a shorted turn is that one single shorted turn kills the Q of the coil. At that point, an 8 ohm peaking coil becomes an 8 ohm resistor.
Again, unlikely that's your problem, but I was just pointing out that a single shorted turn can't be read with an ohmmeter.
That's why ringers were so popular with TV techs. A shorted turn in a flyback, yoke, vertical output transformer, etc. won't show up in a resistance check, but will in a ringing test.
I bought an LC75 Sencore Z Meter brand new back in 1985 and still use the crap out of it. It will perform both ringing tests and test the value of any inductor as well. Smaller inductors that don't ring well on ringers can be tested for their value.
I paid $1000 for the Z-Meter back in '85, but today, we can buy these handy multi-testers for pocket change:
I know these are toys, but I couldn't resist and bought one. Just put any two or three lead part into the socket in any direction, and this toy will identify what it is, what the lead configuration is, and give you things like transistor gain, resistance in ohms, capacitance and ESR, and inductor values. These will check inductors for value but no ring test. But a shorted turn in an inductor will throw off the value. If your TV has more than one of the same part, you can compare them if the schematic doesn't identify the value of the inductor.
John |
Update: I took an NOS RCA peaking coil from my parts supply and measured it. On my Z-Meter, it reads 5.8uh (marked 5.6 on the bag).
On my cheapo mega328 tester, it reads as a 0.2 ohm resistor... I tried several times and did the calibration procedure, but it won't read inductors - it sees them as resistors. Now, this tester is at least three years old and it's possible that this early version didn't read inductors while the later ones (which still look identical) purportedly do.
Incidentally, on the Sencore Z-Meter this 5.6uh peaking coil shows 5 rings.
Lastly, this is an RCA part number 119590. Judging by the part number, I'd say this is an early 60s to mid 60s coil for a color TV, but it likely covered many years.
If anyone wants this, it's theirs for the asking. Email me at
delstv@aol.com
John