[Boatanchors] Re: SX-100 Mk 2 Problem

[Bill Stewart]

Thanks to all who have made comments so far. Man this copy & paste is neat...I learned something.....

Dave, W4QCU wrote:
Your assessment of R23 looks correct to me.  Wonder if
R23 burned up because C23 has low resistance to
ground.  What is R from pin 1 of the 12AT7 to ground? 
I MEASURED AN OPEN CIRCUIT

I wonder about the 6BA6.  Perhaps the tube is not
drawing current.  Do you have about 2200 ohms from pin
7 to ground?
I MEASURED A SHORT ON PIN 7 TO GND. PIN 2 TO GND SHOWS ABOUT 2 1/2 OHMS WITH A SLOW DRIFT DOWN. MAYBE THE CAP ACROSS THE 22K IS SHORTED.

Jack,  wrote:
HI,        THE  BBOD strikes again!  check continuity from plates of  V12
to ground, should be more than 100k.
the .01 mfd, a BBOD shorts and the entire plate voltage is dropped thru
the 100k resistor.
early sets had the black, striped things which do short and show just what
you describe..(BBOD=BLACK BEAUTIES OF DEATH).
all of those that you see under the main chassis must be replaced  except
the ones in the selectivity control, those are not sensitive to a small
amount of leakage. 
I MEASURED AN OPEN CIR. FROM V12 PLATES TO GND. 
AH YES, THE FAMOUS BLACK BEAUTIES. MOST OF THE CAPS UNDER THE CHASSIS ARE "TINY CHIEF". I ONLY SEE ONE "BB" (BLACK, ROUND, WITH COLOR BANDS). SHOULD THE "TINY CHIEF" CAPS BE REPLACED AS IF THEY WERE "BB'S". I'LL KNOW MORE ABOUT WHAT'S IN THE SUB-CHASSIS WHEN I OPERATE.

Greg, KX4R wrote:
It's gonna be a job...but the little sub chassis will have to be removed
.....culprits are the screen resistors of those tubes. Old carbon comp types
which have changes value drastically
FROM SOME OF MY MEASUREMENTS AND OTHER COMMENTS, THERE'S PROBABLY SOME RESISTORS DAMAGED OR OUT OF  TOL. I'LL BE PREPARED TO REPLACE ANY THAT ARE OUT OF TOL.

And Larry W0OGH pretty much said it all...."BAH" and got rid of his problem receiver.

Well I'm holding my breath, cinching up my shorts and gonna jump in. I have labeled the wires, made a sketch and started unsoldering the wires. As several suggested, I'm taking my time. I'll post my findings later. Many thanks for all the comments. You've all been a great help....Bill K4JYS