Fender Blues Deville 410 Internal Speaker Jack Impedance & Head Conversion

[forloveofivy]

Hi All, I recently purchased an early 90s Fender Blues Deville 410. I decided to take on a fun project to convert it into a head. The biggest question I have at this point is if anyone knows what ohms the internal speaker jack is good for? I want to be sure I am using the cab properly. I know in the manual I read, it lists that you can use the external speaker jack with an 8 ohm cabinet, but there is no mention of the way the internal speakers are wired. Further, I am wondering if I should even use the internal speaker jack as the output to the cab, or if I should just use a "dummy" cable in the internal jack then run the external jack to the 8 ohm cabinet. 

There was a similar question on the following thread, but I am just looking for reassurance as to if I should be running the converted head into 4 ohms or 8 ohms on the cabinet.
http://unofficialwarmoth.com/index.php?topic=11419.0

Also more generally, are there any other speacial considerations that anyone knows I should consider when doing this head conversion? Has anyone else done a similar conversion? Thanks.

 

[mayfly]

according to the schematic here,

http://www.blueguitar.org/new/schem/fender/blues_deville.gif

the main speaker is wired to be 8 ohm.  From what I see on the schematic, you can just connect your 8 ohm cab directly to the 'internal' speaker jack and you'll be fine.

Don't use a dummy cable with the external jack, or the external jack by itself.  It's all wired with the OP transformer to select the 8 ohm tap with something plugged into the internal jack, but then switch to the 4 ohm tap when both jacks are used.

Trevor