Hoffman Fender Blues Junior Conversion

[EL34]

People email me and ask if I make a BJ tube board for 8 Pin Octal sockets

You don't need a board for octal sockets
The chassis holes are the perfect size to mount an octal socket right into the chassis

Take one of my BJ tube boards and cut off the last two holes where the 9 pin el84's are mounted.

There you go, 3 x 9 pin socket holes and then mount your last two 8 pin sockets right to the chassis

http://hoffmanamps.com/MyStore/catalog/BoardBuilding.htm

[bakerlite]

If anyone has a moment who has built one of dougs Blues Junior boards I'd be interested to see what ballpark ye are getting voltages wise -
http://el34world.com/charts/valve/ValveData.php

[EL34]

I have the important voltages on the schematic
http://el34world.com/Hoffman/files/Hoffman_BluesJunior.pdf


What voltages do you want?

[bakerlite]

just ballpark figures for v3 as I'm not sure what should be going on there , everything else looks good

[EL34]

Something close to what the Stout has here on the schematic
http://el34world.com/Hoffman/files/Hoffman_Plexi_6V6-V2.pdf

[purpletele]

Doug,

Simple question.  When you design turret boards from an existing PCB, The Blues Junior for example, are you essentially utilizing the same component designation as the original schematic?  I saw a post where someone was going to implement some of Billm Audio Mods and they were citing changing the C25 Filter Cap to x, and changing R29 to Y.  I understand that reverb is not in this circuit and replaced with the Meat Control. 

I was considering implementing a Presence control and a Clean Boost Mod left over from a previous mod project, and looking for a reference point for understanding.

Thanks   

[sluckey]

There is no correlation between Doug's part designations and the original BJ. Doug's circuit also has some minor changes. Put Doug's schematic and the original BJ side by side and you'll quickly see the differences and the reason why it would be very difficult or impossible to correlate part designations.

[purpletele]

Sluckey,

Thanks.  So the serious reverse engineering is seriously reverse engineering.  That's what I figured, but then you hear people referencing components from a PCB and you start wondering if you missed some article or notes on the board development.

 

[EL34]

I take the original schematic and go from there.
Some minor changes happen here and there usually

[Zurdo]

Hi Doug,

If I wanted to build a blues Jr circuit from scratch instead of converting an existing JR, does the parts kit have everything I need to build the board and controls minus the trannies and I'm assuming no reverb? I have a head cabinet that needs a project and I thought I would do a JR type amp in it.
http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&thispage=Amp_BluesJuniorConversion.htm&ORDER_ID=!ORDERID!
Also wondering if you know anywhere who has a chassis layout/cutout diagram?

Thanks a million!

Brian

[EL34]

Hi Brian,
Not really sure what you are asking?

You can look at all the parts on my parts list and decide if it has everything you need.

If you don't have an existing amp to start with, then you would need all the things that are in an amp carcass and not on my parts list here.
http://hoffmanamps.com/MyStore/catalog/PartsListIndex.htm

[purpletele]

Brian,

I am esssentially building from scratch as we speak.  I have been getting some great help from another members via photos and e mail advice.

I have two spare chassis for a combo unit.  The chassis fits into the Mojotone Blues Junior or Deluxe 1 x 12 Combo.  The tubes tube holes and the transformer cut out are in place.  The rest of the holes need to be cut.  I have a template for a control panel via Precision Design. 

I am utilizing 6v6's for power tubes.  That needed the help of a small transformer.  That info is available if you want it.

Let me know if you are interested in the chassis or photos.



BV

[EL34]

Zurdo,
If you are building an amp from scratch, then you will need to figure out what parts you have or don't have.

Just take my parts list and start checking off everything you need or don't need.
if you already have some of the parts on my list, scratch them off the list

If you don't have a donor amp then you will need all the parts that are part of that

A chassis and transformers
Maybe a cabinet and speakers also

It's a good idea to follow this procedure so you have a good understanding of your project and how it will all go together

[EL34]

Here's an example of a really clean Blues Jr build by a forum member
https://el34world.com/Forum/index.php?topic=25209.0

[EL34]

I got this cool email from a customer this morning


Doug,
Just turned on my Blues Junior Conversion I did with your kit and documentation for the first time tonight. 
I didn’t know what to expect going in regarding how different the amp would be sonically, but this thing has blown my mind. 
What stands out the most is the natural overdrive I am able to now finely control. 
I am very, very happy with the results. 
The build was straightforward and uneventful thanks to all your documentation you make available on your site.

Anyway, just wanted to reach out and say both thank you and well done on a great conversion package!