Ampeg B15N - speaker connection / soldering

[boroman]

OK guys. I have been soldering new speaker cable to my 70s B15N and wanted to ask where on that switchcraft 4-pin connector (from left to right: 1,2,3,4 pin) is [+] and where is [-]? the pins #1 and #4 are speaker connections as I see, but no knowledge about +/-....

 

[coreyfyfe]

Here's the service manual @Vintage-Blue has on his website for the late 60's B15NF which is probably the closest available on that site to your amp.

Green (+) goes to pin 1, black (-) to pin 4.

There may be later schematics available in the portaflex wiki above but I went with that one because Mark has redrawn a lot of them and they're clear and easy to link. I think there was a time when ampeg was doing green for negative and black for positive? But that may just be me mis-remembering.

 

[beans-on-toast]

..and pin-2 and pin-3 should be jumpered together at the cabinet connector.

 

[boroman]

Thanks. I have already jumped (by factory) 2nd and 3rd. I'm asking because it's hard to do a "9v battery test" t because 4pin goes straight to the head..