bad hum Blues Junior

[ctcpete]

Thanks, guys. I just pulled out the amp, its been off for 2 days, powered up and the thing is quiet, had a mild hum with the back cover off, went away with back cover installed. It's plugged into the same outlet as well. Tried to jostle it a little, the hum won't occur. I did leave the ribbon cable for V1 flat down over the solder connections for v1. I assume this is no good due to heat off the tube I'll reposition it.
I'm looking at the schematic and I think V1 12ax7 is first in line from the input (preamp tube?). I need to review all the tube stuff I tried to learn during my last mods about a year ago. I'm going to pull the board and see if I can duplicate the problem.

I'm considering doing a transformer upgrade and maybe a different speaker (mine has the made in Italy Jensen Special design) but first I need to make it more stable. I've heard that the illonois caps may be less than optimal, they don't appear to be leaking but I may swap them out a (Blue atoms are ok I assume).

Will report back, thanks again.

[guitician]

Too bad about Fender quality. My bro has a Blues Jr. too. When I played it for the first time I noticed that the treble control didn't work. So I opened it up to find it's cap with one of it's leads in the hole, but not even soldered. It may have been touching the edge of the trace when it was tested at the factory, then after a bump or two, it stopped working. All was fine with the amp for a couple of years, now the amp is dead, and it doesn't blow fuses, what's up with that

[ctcpete]

I removed the PWA and found nothing obviously wrong. I removed the tube mount PWA and retensioned the pin connectors and cleaned out with contact cleaner. It's running pretty quiet now. I installed new power tubes and re biased.

The amp is a 2003 model so I'm just going to replace all the electrolytic caps. I think there is some kind of oscillation going on. When I hit a sustained note at higher volumes, there is an audible buzz/burp/fart at the end of the note.

Thanks for the advise.

[ctcpete]

Would I be ok only replacing the filter caps (22uf X3 and 47uX2..(I have a stiffened power supply). I ordered these caps through Bill"s mod kit, only 20$ not much more than Mouser. Any need for replacing other electrolytics? I don't have the time to test them etc. I'll also do the output xformer upgrade and a 3 way power switch with standby upgrade at this time. Probably in a few weeks.

I must say I love what all the mods have done to my Blues Junior tone wise etc. but I sometimes doubt the actual platform with the PWA and ribbon cables etc. Hopefully I can make this a stable amp (my other one is a 73 Twin I restored and black faced last spring, hasn't been powered on since...big and loud, hopefully still functional).

You experts on this site are true artists and truly generous with your knowledge I wish one of you where local to me in central NJ..you'd have my business for sure (let me know if there are any good amp techs in my area..ones I know of are not local..Ocean county). I went to tech school in the early 80s and was taught about many of these passive components but then worked as a field engineer (electro Mechanical) for many years with hardly any component level analog trouble shooting, now doing a career change to a medical field+ kids+work = little time for amp maintainence, let alone guitar playing.
Once my Blues Junior is "done" (one way or the other) I may bite the bullet and look for something new and reliable with crunchy blues tones (does it exist at a reasonable price point)?

Thanks again, sorry for my long windeness, currently locked up with young kids, no adults to talk to!

[jimmylee]

Having the same issue with my Jr. I know this is an old Thread but did you ever fix the hum. I've upgraded all caps, tubes, replaced 2 tube sockets. Hum is still there. Also when I touch the Ribbon connector at V1, the far right side, of it the BLACK or first wire I pick up a strong AM radio signal. Any idea what that could be. bad connection etc ?? just curious if you ever got down to what the hum was, on mine it is especially annoying because it gets louder when using pedals etc.... compression, and univibe are the worst. When the pedals are engaged hum is very loud and annoying... take pedals to another amp...no hum! Could this be a grounding issue in the Blues jr. I did do all mods myself, maybe I missed something. I've gone over every solder joint with a magnifying glass... can see any bad ones