Fender Amp Mod - FM212R add a extension speaker cabinet

[BILLYL]

My son just got a Fender FM212R amp.  It has 2 12inch speakers but he wants to add a speaker cabinet to it.  The amp has no external speaker jack.  Can I simply add a output jack - by tapping off the internal speakers.  The manual says that the speakers are wired 4ohm.  I am concern that I could do damage to the output transformer.

Any suggestions would be appreciated

Thanks

Bill

[boogietube]

Yes you can do that .
Here's a link to figure out the proper wiring:
http://colomar.com/Shavano/construction.html

Your total impedance should not exceed 4 ohms.
Usually. they are wired in a series parallel arrangement.
Check out the 412 wiring  diagrams on that page.

[BILLYL]

Thanks-  that will do it.........................

Bill

[Ben N]

Your total impedance should not exceed 4 ohms.

And there is the rub.  It is practically impossible to maintain the same impedance load if you plan to keep the combo speakers connected.  I don't really know, but methinks that SS amps are more sensitive to changes inn load than tube, so you should tread carefully.  If you are planning to disconnect the combo speakers and attach a separate 4 ohm cabinet, tat would work fine.

If your son is looking for more volume, maybe subbing more efficient speakers into the combo is the ticket.

HTH,
Ben

[BILLYL]

The plan is not to use the combo speakers - so when you plug in the cabinet - the combo speakers will be off.

So that should work.

Thanks
Bill

[Ronsonic]

You can simply add a jack. connect it to the circuit board and then create a speaker cable to go from the speakers to your new jack when you want the internal speakers.

Just don't plug anything under four ohms into that jack. Leaving it open or plugging in a 16 or 8 Ohm cab will be fine.

There is no output transformer.

Ron

[BILLYL]

Thanks Ron - good idea

Do happen to know where I can get a schemo of this amp?

Thanks

Bill

[darron]

The FM 212R speakers are wired in Parallel. So just put a switched socket on head and hookup the wires that are going to the speakers. Never run it while there aren't speakers plugged in though... That could be very risky. While you are working on it, shield those rca cables going to the spring reverb as they are VERY noisy!

What does he think of the amp?

[BILLYL]

Darron-

So for the jury is out on the amp.  I think he likes it - but it looks like he may be trading it in for a Crate head. 

Bill

[Ronsonic]

It is a question of taste as much or more than one of relative quality - but - going from a low end Fender to a Crate seems more like a lateral move than a step up. Everybody has the same automated board populating machinery and wave solderers. Price point to price point all the mass market crap is comparable. I'm thinking that if he needs/deserves/could use something better than that Fender he isn't going to find it in the Crate line. You can chew up a lot of money with lateral moves between product lines and end up not any better off.

I'd suggest living with the Fender (or whatever) until the budget (and knowledge base to use it wisely) is there to get something really good. If not a lifetime amp, something a full step closer.

Anyway, that's just the opinion of a cranky amp tech.

Ron