Blues Jr. help

[cjhastings]

So I ended up buying a 90s American made Blues Jr on Craigslist a couple of months ago. I got a pretty good price for it, and I never had any troubles with the amp until a few days ago. All of a sudden, the amp has started going crazy. The amp will start making a really loud buzzing sound and it won't stop even when the volume is turned down. This happens randomly a couple of times each day.
It doesn't seem like any signal from the guitar is going through when the amp starts acting like this.
The noise does stop temporarily when I turn off the amp and wait a few minutes before turning it on again, but it still comes back after a while.

Has anyone had any similar experiences with their blues Jr, and if so, how did you fix it? I'm a high school student. I'm not very knowledgable on electronics, so any help is appreciated.

Thanks,

-CJ

 

[PFDarkside]

Re: Blues Jr. help

Sounds like it's time for new power amp tubes.

 

[ehdwuld]

Re: Blues Jr. help

heat induced tube failure

its a tube

its a preamp tube (the small ones)

the buzz may be an arc across a bad solder joint on the tube mount
mine did this on the reverb tube (Carvin Belair)
remove the Tubes
remove the Pan
touch each tube socket solder joint with iron till solder reflows
reinstall pan and tubes

but swap tubes first, that probably will solve it

 

[zzmoore]

Re: Blues Jr. help

Random...and not constant.?
Certainly could be a bad tube.
Also could be a Bad/Dirty connection at the input, tube socket, or even the output.
Check all the easy stuff first:
1.Tubes
2. Anything that slides in and out of something else E.g. a tube or cable.....pots and jacks.

 

[cjhastings]

Re: Blues Jr. help

Random...and not constant.?
Certainly could be a bad tube.
Also could be a Bad/Dirty connection at the input, tube socket, or even the output.
Check all the easy stuff first:
1.Tubes
2. Anything that slides in and out of something else E.g. a tube or cable.....pots and jacks.

Yes it's totally random. Sometimes I can play for an hour or two without any issues, but other times I have to restart the amp every 10 minutes. I'll do a test tomorrow and check the tubes. Not sure what else it could be...

 

[ehdwuld]

Re: Blues Jr. help

is there an effects loop?
I totally forgot
the effects loop

short patch cable
jump from fx in to fx out

 

[cjhastings]

Re: Blues Jr. help

is there an effects loop?
I totally forgot
the effects loop

short patch cable
jump from fx in to fx out

No fx loop on the version I own.

 

[jeremy]

Re: Blues Jr. help

my guess is its the input jack. on these amps it is soldered directly to the pc board. i had a '95 blues jr which i loved and played hundreds of shows with but i replaced the crappy jack with a normal switchcraft one with wires going to the board rather than the direct connection. never had a jack problem again. could be tube failure too and that may be easier to check out, pull one tube, turn the amp on, let it sit for 5 minutes and see if anything happens. if not, put that tube back in and pull the next one. you wont hurt anything by running the amp without a tube just dont play through it

 

[Chickenwings]

Re: Blues Jr. help

toobs first. All other troubleshooting later.
If it turns out the toobs were not the issue, then you have a spare set for gigs.
At last 9 times out of 10, any problem with a tube amp is from one or more tubes going sideways.
Think of them as car tyres...they inevitably wear out and need replacing.