OK still troubleshooting but found 2 more clues.... I pulled all the tubes and the AC4 power resistor R3 in the 250V line is now cool to touch and V is 260V with NO tubes in. When OA2 is in place (only OA2) R3 is too hot to touch and V drops about 12V.
2nd Clue I finally found what smoked in the chassis. It was hiding under a switch shaft in the RF compartment. The 'smoker' was R30 the 68 ohm 1/2 watt resistor on V5 (final) So I think maybe the tube had a grid to fil short and took out both circuits. I am still not getting a spot signal. R3 is still too hot when OA2 is 'IN' OA2 is blue not shure otherwise if it is good? Problem may be on the 150 V line as that powers the VFO (I think). Still have the tubes out. Paul K3PG in 'snowy' MD pix on http://pgerhardt.blogspot.com On Thu, Feb 4, 2010 at 11:31 AM, Paul Gerhardt <phgerha...@gmail.com> wrote: > Turned on my Working T4Xb and smoke came out the bottom of the rig which I > can't see for some reason. The filimant fuse (8A pigtail lead fuse near the > 3 big power resistors) is open so replaced that, then no 250 V B+ and found > R3 1K 5 watt resistor to be open. Both of these were 'effect' and not cause > (I suspect). I changed R3 and got 150V and R3 is hot. Unhooked the yellow > 250V wire to the rig and V is good about 270V. Turned power OFF and > measured Resistance on yellow wire and it is low only about 150 ohms. Last > thing is always suspect and for this the last thing I did a few days ago was > install some used FleaBay finals which worked ok it seemed but were very > weak only about 60-70 watts out (maybe one was not working?) Put the bright > light on the bottom and compared to photo I took before and fail to 'see' > any burned parts on the bottom but there was smoke and I think it was from a > hot wire and not a componet. Will probably change the finals back to the > 'other' weak ones that were at least putting out 120W into the Cantenna and > see what is pulling the 250V B+ line down. > Any ideas on this one? > > 73 > Paul > > > > > -- > Paul Gerhardt > K3PG > http://pgerhardt.blogspot.com > QRP ARCI 6674 > FP 274 >
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