late 70's UL super reverb speaker impedance

[dinkotom]

Does anyone have this amp? I'd like to know the individual speaker impedance for this amp, schematic says 16 Ohms:http://schematicheaven.net/fenderamps/cbs_70w_mstrvol_pullsw_super-pro-bmstr_rev.pdf But I have four 8 Ohm speakers (they look stock, blue fender label, CTS I guess) in my amp, paralleled total load measured is 2.3 Ohms. The back of the amp says 4 Ohm minimum load. My best guess is that the previous owner replaced the speakers with incorrect impedance. Or Fender screwed up...

[sluckey]

I agree.

[PRR]

Check if your jacks exactly match the schematic.

As I read it:

Grn-Blk is 4 Ohms. Grn/Yel-Blk is 2 Ohms.

No plugs, the amp is shorted.

Plug to left (on schem) jack: connect 4 Ohms

No plug to left jack and plug to right jack: connect 2 Ohms
Plugs to both jacks: connect two 4 Ohm loads

Personally I'd incline to ONE jack and a 2/4 Ohm selector switch. Trust the user to do the right thing.

[drgonzonm]

I am wondering if one of your 8 ohm speakers has failed.  2.3/0.75 = 3 ohms, which is very close to the 3.2 ohms expected.  I would verify that I did not lose a speaker. 
FYI One amp manufacturer would consider your 2.3 ohm load, if dcr, to be a 4 ohm nominal load.  (Sound Electronics, the current company that once made the sound city 120.)  I do agree with Sluckey. 

As PRR has pointed out, the schematic shows both a 2 ohm and 4 ohm tap.  It won't hurt to plug into the 2 ohm tap. 

I would also verify that the o/t is also correct.  Look for part numbers on the o/t, then cross reference on the hammond transformer website, for specifications.  Fender didn't always put the correct parts in their amps.  I found reference to the 013897 part number on the bustedgear website.  I did not find that part number on the hammond website. found reference to same part number on Mercury Magnetics website, provides additional basis for PRR's 2 and 4 ohm tap info. 

You did not say whether or not this was dcr (direct current resistance) of the load.  It is my understanding testing for nominal load is a lot trickier than checking dcr. 

I would feel more comfortable wiring the speakers for an 8 ohm resistance. 
The same manufacturer also shows a diagram on their website, on how to wire the four 8 ohm speakers to have an 8 ohm resistance. (The website shows the wiring for 32 ohm using four 32 ohm speakers) it is a form of series-parallel wiring.