blues JR fried resistor

[stevesamps]

I have this blues JR, with the first power supply resistor burnt, this is the 2.2K (r47 I think)
that feeds the screens, I guess my question is what is making the short
to ground? because I replaced it with a 5W 2k7 and its baking that one now!

I even tried clipping the diodes that are there for protection
it seems pin 9 on the 84s are shorted to ground or the heater supply or
something that makes all the current in the amp burn right through
that resistor.

anyone recall anything like this maybe the board or that crappy ribbon cable?
or perhaps a very obvious component I seem to be missing?

I did use new tubes that I know are working
I did a quick voltage check and the B+ was on both plates.
so I think the OPT is still ok,

The last thing I did was clean all the carbon off the board from burnt resistor
but it had no path to ground, I guess a filter cap could short, but there
really is not much there if the power supply had become that "short"

Steve

[Gibsonman63]

I would suspect a filter cap because it is the only component with a relative short life expectancy and they are known to short. Check for ones with buldging ends. Some sights claim that putting in quality filter capacitors will tighten up the bottom end as well.

If you power up with a light bulb current limiter while you are troubleshooting you won't have to change resistors and scrape carbon off of the board.

[stevesamps]

I was kinda thinking that too but the amp is so new
like 2004, I will try the cap, and maybe at least the variac
for some measure of sanity

I have never had a shorted filter cap that was this new
that may have been why I was looking elsewhere

[Gibsonman63]

In the last two years I have been changing a lot of power supply caps in relatively new equipment. I guess it comes with competition and hitting price points... plus it gets hot down here outside in the summer and some of the equipment doesn't like the heat much.

[Enzo]

New, schmew, parts fail. There is a difference between a part just failing, and parts at the end of their useful life. ANything can fail at any time, there is no "not old enough to fail."

If pulling the tubes doesn;t stop the burn, then the cap is mostly all that is left. Since it is the screen node that is loading down, things before that resistor won't affect it. In other words the powe rtube plates or the OT itself won;t affect that resistor.