Zenith Color Roundie Alignment with B&K 415

[old_tv_nut]

Originally Posted by bhegges

... I kept the probe set to 75 ohm[/LIST]... I assume I should adjust the specified coil to get the marker to fall on the pictured response curve in the correct place, but I can also adjust to simply get the highest or lowest scope response for the marker, doing this completely messes up the curve.

...

1) Exactly what probe are you setting to 75 ohms? Is this a scope input setting?

2) What do you mean by "fall in the correct place?" If the procedure says min or max at the marker, it means only that - the vertical position of the marker should be min or max. If the curve ends up looking wrong *at the end after all adjustments have been made*, there is something wrong with your setup or you made a mistake earlier in the procedure.

It is possible the curve won't look right when you are only part way done.

[bhegges]

The 75 ohms is the setting on the B&K 415 Signal cable, you can select 75 or 300


"fall in the correct place?" maybe not the best way to describe but as I adjust a coil the response curve on the scope moves right or left which has the effect of moving the marker up or down

• Linked below is a small video of adjusting the 41.25 coil above an below what to me is the peak which I assume is the minimum response
• https://imgur.com/VRn62J5
• 

I agree on needing to bring it all together, I will follow up with where I am at in a bit.

[bhegges]

OK here is where I am at:

Scope measuring on test point C1, all 7 markers are turned on, note the B&K 415 has a 41.67 marker vs a 41.75 marker which is what Zenith references. Directions are to make adjustments to the 41.25, 47.25, and 39.75 traps (L1, L2, L3) for minimum responses, accuracy of trap attenuation and marker locations.





Scope measuring on test point C2, same 7 markers are turned on. Goal is to make adjustments to the converter plate coil and 1st IF coil (T1) to match the response and also to adjust the 2nd and 3rd IF coils (T2, T3) for maximum response and to approximate the response curve.

[old_tv_nut]

Originally Posted by bhegges

The 75 ohms is the setting on the B&K 415 Signal cable, you can select 75 or 300


"fall in the correct place?" maybe not the best way to describe but as I adjust a coil the response curve on the scope moves right or left which has the effect of moving the marker up or down

• Linked below is a small video of adjusting the 41.25 coil above an below what to me is the peak which I assume is the minimum response
• https://imgur.com/VRn62J5
• 

I agree on needing to bring it all together, I will follow up with where I am at in a bit.

Is the vertical input of your scope set to DC? it appears it may be set to AC and the whole curve may be shifting up and down, confusing the measurement of the actual vertical position of things.