Fender Pro JR. problem....

[allmodcons]

I have a tweed Pro Jr.made in USA,1994 I think(1994 printed on the board...).After switching on,I heard a "pop"....Now,although the amp works,its fairly muddy,without the usual fabulous note clarity and crispness-not a pleasant amp to hear,for sure....the board shows no obvious blown resistors etc....I swapped the speaker,and tried 2 other complete sets of tubes to no effect.The only noticable thing is the barely glowing 12ax7's,and the really hot el84's(I have another Pro jr.,that I can a/b with.).My question is: What would you check first,and does anyone have any ideas what may be the likely culprit?? THANKS!

[allmodcons]

...Fender Pro Jr .problem-update-

Well,I have finally gotten back to troubleshooting this little Pro Jr. So far I have replaced all tubes with known good tubes;replaced OT with known good one;replaced several caps and resisistors with upgrades;replaced the speaker with a known good speaker.I have checked most of the test points as per the schematic("B" revision)... I havent suspected the IC caps yet--should I?? The amp has seen little use since 1994,and worked beautifully until the "half power/muddiness"happened....hmmmm...anyone have any ideas for me??

[rpm]

Have you checked the conjunctive filter across the secondary of
the output transformer? It's just a filter and a cap. I've seen those
tiny little resistors cause the problem you describe.I'd use a higher
wattage one to replace it. rpm

[drewl]

Are all the output tubes amplifying?
You may have blown a screen resistor causing only one of the output tubes to actually work which yields a crappy muddy lower volume tone.

[allmodcons]

Pro Jr.problem update

Thanks to rpm and drewl,for your replies! Well,I've got the Pro Jr.putting out massive volume again(relative to its little size,that is ) After checking all the DCV specs and having everything come very close to the Fender schematic values,I checked every resistor in there for values and found everything really close to spec....so I figured that since I wanted to eventually upgrade some caps and resistors to better quality,I would just change 'em out...(lazy troubleshooting,eh??!!) Of course,changing out the 100 ohm plate resistors with 100,000 ohms didnt exactly help the lack of volume issue( gotta get some glasses to read these schematics you see.....)Anyway,the Pro Jr. is back to its nasty self again,although with a little bit more hum than before....hmmmm...A couple of questions though:
Is there much value to upgradeing the Illinois Electrolytics to Sprague etc...big price difference...but since I've got it on my bench,maybe its wise to change them out---or just a waste of money....??
Are "on-board" ohmmeter checks for resistors accurate??Seems to me that they wouldnt be,but in this case,each value was good..
THANKS!