Betty R6_MB mainboard no power

[pc1staid]

Hi All,
Got the above mentioned board with no power.
It doesn't take a lot, I am confused.
This is what I have done so far:-
19.5v going in. Followed this thread:- https://www.badcaps.net/forum/showth...t=87414&page=1
Everything seems to tally with the advice offered. Get the correct readings of 19.5v where is supposed to be. On the two large coils ( pic 2) where I would expect the 3v and 5v to be I get nothing. However on the + of the power button there is 3.1v, so obviously the 3v is being produced.
Here is the confusing part, every fuse I get 19.5v with exception of F2 which has nothing. Tested fuse and its good. I did discover that PU9 was hot (pic 1). When it cooled down I found PC189 just to the right was shorted to gnd on both sides. Removal of PU9 and PC189 resulted inthe short going on pin 9 but still evident on pin 8. Went back to PL16/17 and I assume the PL17 is the 3v line. Found both sides had a short when PU9 was in situ. Removal of PL17 along with PU9 yielded no short on the side closest to PQ45 ( for now I will call this pin 2), still short side near PC335 ( pic 2). Removed PC339 and the short remained. So what I did was injected a little voltage onto pin 1 of PL17 and applied 0.8v and immediatly a cap on U56 ( pic 3 and 4) went supernova. The cap is cracked. In these pics you will see that I have just moved the cap to one side. the short on PL17 is now gone. Checked pin 8 of PU9 and there is no short. Replaced PU9 and PC189 and the short has returned. PC189 when removed has tested correct.
Thanks in advance oh guru's of the forum.

So after this long ramble, my questions:-
Should all the fuses all be showing the 19.5v input voltage?
I suspect PU9 to be the culprit for the short as if I remove it and leave PC189 in situ, the short goes, would that be correct?
The cap thats gone on U56, one side shows 2.5 ohms/ 0.100v to gnd and the other is 0.5 ohms/ 0.066v to gnd, am I looking at a failed U56 and if not is is safe to run the machine with this cap removed as I do not know the specs for this cap.

I have ordered a new PU9 regardless just in case any of you confirm this is the most likely cause.

[mcplslg123]

Re: Betty R6_MB mainboard no power

U56 is very likely gone .

[pc1staid]

Re: Betty R6_MB mainboard no power

U56 is very likely gone .

I assumed as much. Mainly as all fuses across the board all had the input voltage. Like the one by the battery, I would have guessed that would have been in the 12v area not nearly double that.