R634 getting too hot: you may be right, of course, that you inadvertently nudged it against some other electrically-active point (including chassis), but I would check C610 for leakage. C610 may even have re-formed itself, hence the heat from R634.
As for RV601 at end of its travel, if the resistors in series with it check out O.K., I'd suspect C605 (0.25 µF) as leaky. There is always the possibility of an internal short in V607, of course, but then a check at the anode (pin 6) should reveal all: drwg. indicates + 50v., which sounds about right. If much less than that, the valve is passing too much current, possibly due to a leaky C605. Of course, if you fancy an arithmetical exercise, you can always calculate the voltages at each end of RV601, assuming that the grid current of V607 is negligible in comparison to the resistor drain current.
I've just had a look at the CRT drwg.: hmm.
If you're poking around in the area of the mains transformer, keep well away from the LT4 winding, since one side of it is connected to -1.25 kV at pin 4 of the C.R.T. Yo! 
Now you and I know why they've done that (to minimise the h-k voltage stress), but even apart from safety reasons, I still don't like it since it places one helluva strain on the insulation-to-core of the LT4 winding. It's obvious that the mains xfmr. for this item is a 'special'. Should it 'go down', I reckon that you'd be well and truly up the Swanee! 
Al.
As for RV601 at end of its travel, if the resistors in series with it check out O.K., I'd suspect C605 (0.25 µF) as leaky. There is always the possibility of an internal short in V607, of course, but then a check at the anode (pin 6) should reveal all: drwg. indicates + 50v., which sounds about right. If much less than that, the valve is passing too much current, possibly due to a leaky C605. Of course, if you fancy an arithmetical exercise, you can always calculate the voltages at each end of RV601, assuming that the grid current of V607 is negligible in comparison to the resistor drain current.
I've just had a look at the CRT drwg.: hmm.
If you're poking around in the area of the mains transformer, keep well away from the LT4 winding, since one side of it is connected to -1.25 kV at pin 4 of the C.R.T. Yo! Now you and I know why they've done that (to minimise the h-k voltage stress), but even apart from safety reasons, I still don't like it since it places one helluva strain on the insulation-to-core of the LT4 winding. It's obvious that the mains xfmr. for this item is a 'special'. Should it 'go down', I reckon that you'd be well and truly up the Swanee! Al.
