Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: HARodgers on February 25, 2018, 03:31:33 pm

Title: Blues Jr Conversion Switchable Rectifier
Post by: HARodgers on February 25, 2018, 03:31:33 pm

Hi,
I'm building a Blues Jr turretboard conversion, and am looking to add a switchable rectifier on a separate DPDT toggle switch (tube rectifier - standby - solid state rectifier). I've found a schematic for this on the super reverb (http://el34world.com/Forum/index.php?topic=17671.0) but wondered how this would need to be modified to fit the blues junior (namely due to the different transformer and lack of choke) and how to calculate the value of the additional resistor for the rebiasing when switching - or if it would be best to use a trimpot.

Also, would it be best to use a 6CA4 for the tube rectfier, just as it uses 6.3v on the filaments?

Cheers

Title: Re: Blues Jr Conversion Switchable Rectifier
Post by: sluckey on February 25, 2018, 04:09:19 pm

You can't use the first circuit because the BJ PT requires a bridge rectifier.

In the second circuit the bias pot will not adjust anything. I doubt that circuit has ever been tested.

Title: Re: Blues Jr Conversion Switchable Rectifier
Post by: ginger on February 26, 2018, 07:56:19 am

Just use SS

Title: Re: Blues Jr Conversion Switchable Rectifier
Post by: ginger on February 26, 2018, 08:01:26 am

Well , after i posted , I remembered what it used to be like , when i started building amps . you SHOULD use a switchable rectifier for awhile... for me , like most mods, it wasn't worth it