Fender Blues Junior Re-Cap and Mods Part 2 Let's do the Bias
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- čas přidán 5. 09. 2024
- In part two we do a major bias mod, thanks to RSD sounds. This bias module we use in this video is fantastic and easy and quick to install. Once the amp is biased we give it a demo.
• Fender Blues Junior Pa... This is the link to Part One if you have not already seen it
www.rsdsound.c...
www.ampworks.c...
• The easiest way to Do ...
Thanks for using my Blues Junior bias mod kit! Glad it worked well for you. :)
Hello Rowan, thank you. It's a brilliant bit of kit. Every Blues Junior should have one fitted. Take care.
Great stuff! I was given a dead BJ3 that needed both transformers replacing and got it up and running - then everybody I knew who was into amps screamed at me to do the bias mod. Rather proud that I discovered the mains transformer issue myself - it just did not make sense that the schematic showed it with a 240 option, and clearly the inside of the amp showed it at 230. I learned years ago about the problems of an incorrect TX impact on plate voltage with an old Traynor YGM3 I have that had had a fire before I got it, and had a 220 TX put in. Tubes lasted 6 months at any time - heater voltage was around 7.3! Correct Hammond one in there now. Going to try for the little tone mods now and see - lovely twangy/dynamic playing btw, just my style!
Hello. Sorry for the late reply. I do try to reply to all the comments, but i get such a lot now, I get behind with them. Sounds good . You know your stuff. If ever you need anything, parts and bits and bobs, drop me an email. I just checked out your website, brilliant work. Thanks for watching and take care.
Great stuff Martyn. I fitted the RSD Sound bias trim pot mod to my BJ.. As I'm not a tech I measure the bias using the voltage measurement between the output transformer leads with no insulation on them (ha-ha).. It's a bit of a rough & ready system , but it works and I can cool off the factor bias settings which are ridiculous. I wish my 'rusty' playing was as good as yours 😅.. The amp sounded great and I find using a good quality overdrive pedal on the clean setting is a bit more versatile than relying on the amps drive settings.
Hello Pete, thank you. I think the bias trim pot is brilliant. It's called the shunt method. I still think it's the best way of measuring the bias. Take care Pete.
Another great video, and lovely playing! After solving the reliability issues, these juniors can sound really good!
Hello, thank you. They do make good amps once they are set up properly. A better output transformer would be the icing on the cake. Take care.
"Camera error" or operator error, lol? That bias trim pot retrofit is a great product.
I have the Carvin Vintage 16, which is a similar amp, 3-12AX7's and 2-EL84's. The manual says to set the plate current to 40 milliamps at the test point using the trim pot- so 20 milliamps per tube. Then I did the measurements using the same method you used. OT resistance about 90 ohms per side, voltage drop about -2 volts and plate voltage of 373 V. So Idle PD of 8.3 Watts or 60%, which is reasonable. I don't know why Fender couldn't have fitted a bias pot and a test point to measure plate current on the circuit boards of these amps. It's as simple as removing a quick connect from one spade terminal on the board, connecting it to an adjacent terminal, and measuring across the 2 terminals.
Hello Michael. I think you got me there lol. Yes, crazy biasing these amps at 100% when they are fixed bias. Still it keeps us all in business repairing them I suppose. Thanks for watching and take care.