[Heathkit] Resistance in IF CANs in the SB-610 Scope

carl lowry l_carlj at bellsouth.net
Wed Jan 10 10:43:31 EST 2007


Got a question .. perhaps some of the scholars might advise me on.

While redoing a Heathkit SB-610 Monitor Scope I put in a JW Miller 455kc IF CAN .. p/n 12-C2
Miller CAN has 2 coils which terminate at pins #1 & #2   as well the pair #3 & #4
I went across Pins #1 & #2 , & made the proper connections.
Put a 200pf Mica across the coil pins as shown in the Heathkit manual.
Got a real small in height pattern on the CRT probably half to three quarters of an inch in height.
Attempted to tune the Miller IF CAN from the top & really didn't get any change in pattern height.
Then i put a Heathkit 455kc IF CAN in there & boy what a difference in the pattern height..
It was so high that i had to cut my Vertical Gain control pot on the scope back.
Probably a 2 1/2 inch pattern in height.
I was using a HP 8640B Signal Generator set at 455kc with no Gain factor.
Had another Heathkit 455kc IF CAN ( p/n 40-746 ) & put my ohm meter across the 2 pins where I got 10.0 ohms.
Put my ohm meter across pins #1 & #2 on the Miller IF CAN where I got 25.0 ohms.
Also put my ohm meter across pins #3 & #4 on the Miller CAN & again got 25.0 ohms.
Is the higher ohms that i'm getting on the Miller CAN making that much difference on my CRT pattern height ?
Or, could the 200pf Mica be dragging down the pattern as "maybe its not needed" in the Miller CAN ?
Appreciate your suggestions.
73s
Carl, k4zrd


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