Zenith Color Roundie Alignment with B&K 415

[bhegges]

For the alignment directions I have been using the Zenith CM-106 Service Manual which covers the 25MC33 chassis, nearly identical is the CM-105 Manual which covers just the 25MC30 chassis, but there are a few small changes.

Alignment for T4 is slightly different, maybe...

• I just measured the output at test Point C2 and I believe I was overdriving the signal from the B&K 415, reducing the signal does have an affect on the response, I now have it set to exactly 2 volts via my DMM from Test Point C2 to ground.
• I was hesitant to make any adjustments on the tuner but with the above detail I rocked the converter plate coil on the tuner and believe the adjustment may help.

My chassis is a 25MC33, note SAMS lists both chassis under the one folder. These two chassis are very similar with only minor circuit changes I could see in the schematic. Interestingly the IF section on my chassis is wired like a 25MC30.

• C15B on the 25MC30 is a 0.001uf vs a 470pf to ground on the 25MC33
• C17B on the 25MC30 is a 0.001uf vs a 470pf to ground on the 25MC33
• An added 100pf capacitor is present from Pin 6 to Pin 8 on the sound sync amp tube for the 25MC33