Problem with my Fender Pro Junior III

ross1231 · 15th January 2012

Hi, I have owned my pro junior for about 2 weeks and love it. Very happy with the tone. Was always curious to try a bigger cab though, and I own a 2x12 vox which is 16 ohm. The pro junior has an 8 ohm speaker.

After a lot of internet browsing about the pro junior being OK but not IDEAL to run into a 16 ohm cab, and the whole 2:1 ohm mismatch ratio discussion, I gave it a try and played for about 10 minutes. By this time I notice a smell, not like smoke, hard to describe. Like something was too hot..

anyway, I turned it off, and unplugged the cab and let it cool down for half an hour, and now the amp seems to be a bit quieter, particularly between 0 and 4 on the dial, and also breaks up quicker. I should mention that being 2 weeks old I haven't changed the stock tubes out yet, i'm hoping it has something to do with them, but understand it could be the output transformer.. all tubes do still glow. Any help or ideas to further diagnose would be appreciated. Thanks : )

oavelasco · 16th January 2012

The tubes run "melt your skin" hot in a Pro Jr. I've actually seen smoke a few times from burning the plastic on my meter leads when they were dangling a little too close. Its normal, but there is an easy mod that adjusts the bias. This should explain it, as well as a few other things you might want to do while you're in there.

Mod your Fender Pro-Jr!

You pretty much change one resistor (R15) from 15k to a higher value (18-20k) and the tubes will run cooler. And according to this instructable, it does not affect tone. I have yet to try it myself, since I am waiting on a package of 1/2w resistors.

15th January 2012	#1
ross1231 Gear interested Joined: Sep 2010 Posts: 10 Thread Starter	Problem with my Fender Pro Junior III Hi, I have owned my pro junior for about 2 weeks and love it. Very happy with the tone. Was always curious to try a bigger cab though, and I own a 2x12 vox which is 16 ohm. The pro junior has an 8 ohm speaker. After a lot of internet browsing about the pro junior being OK but not IDEAL to run into a 16 ohm cab, and the whole 2:1 ohm mismatch ratio discussion, I gave it a try and played for about 10 minutes. By this time I notice a smell, not like smoke, hard to describe. Like something was too hot.. anyway, I turned it off, and unplugged the cab and let it cool down for half an hour, and now the amp seems to be a bit quieter, particularly between 0 and 4 on the dial, and also breaks up quicker. I should mention that being 2 weeks old I haven't changed the stock tubes out yet, i'm hoping it has something to do with them, but understand it could be the output transformer.. all tubes do still glow. Any help or ideas to further diagnose would be appreciated. Thanks : )

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16th January 2012	#2
oavelasco Gear interested Joined: Oct 2009 Posts: 10	The tubes run "melt your skin" hot in a Pro Jr. I've actually seen smoke a few times from burning the plastic on my meter leads when they were dangling a little too close. Its normal, but there is an easy mod that adjusts the bias. This should explain it, as well as a few other things you might want to do while you're in there. Mod your Fender Pro-Jr! You pretty much change one resistor (R15) from 15k to a higher value (18-20k) and the tubes will run cooler. And according to this instructable, it does not affect tone. I have yet to try it myself, since I am waiting on a package of 1/2w resistors.