[Boatanchors] SX-100 Mk 2 Problem

[Bill Stewart]

I recently got a SX-100 Mk2 which has the following problems: no background noise ("white noise" as the FM'ers say), no signals heard except a very weak local BC stn., no BFO tone heard. The sig. gen. will put through a sig. but I have to really dump in a sig. On doing a few voltage checks I found about .3 Vdc on the plates of V12 (12AT7) which is the 2nd Conv. Osc.; V5 (6BA6), the 2nd mixer, does have B+ and Screen voltages (both are around 255 Vdc, schem. not too clear but looks like the screen should have 90V?) V5 & V12 tubes were pulled and checks made at the sockets. A continuity check from the red-wire end of L7 to the V12 plates shows open. A continuity check from plate pin to plate pin on V12 shows continuity. This would lead me to think that T9 transformer primary is ok. As I see it, that  leaves R23, 100K, as prime suspect (or a bad connection in that area). 

I'm wondering if anyone has had a problem on their SX-100 Mk2 in this area. Also, any second opinions on what I found would be welcomed. The area of question is in the 2nd converter sub-chassis and it looks like a number of wires will have to be un-soldered and the sub-chassis removed in order get to the underside of the sub-chassis. I dont want to do this if I'm barking up the wrong tree. 

Thanks for any comments....Bill K4JYS