77 aftermarket radio woes

[MetalMagoo]

I picked up a 77 280z on trade for some metal work. It's a nugget. 

 

280zx alternator upgrade (brand new with internal regulator) with voltage regulator delete and maxi fuse upgrade (deleted the fuse links and their respective relays)

 

I'm experiencing a weird problem;

 - Aftermarket tape deck from the 90's when this was last on the road. 

 

If the deck is plugged in (12v straight from battery) it won't crank over. In fact it kills everything if I try to turn the car over. If I unplug it, the car will crank. If I turn on hazards those kill all interior electronics, same with headlights, they'll kill everything too. I've cleaned all the grounds in the engine bay.

 

This is all with a battery tender/charger hooked up.

 

I'm wondering, should I have kept the relays? 

 

I do have the Haynes manual, as well as wiring diagrams and a meter.

 

This is weird. I did swap the ignition from my 78 before the upgrades and everything worked fine. The factory radio harness is a bit buggered. Probably should start there. 

[Phantom]

I would suggest you spring for a Nissan Service Manual.  They have some excellent wiring diagrams in them.  Sounds like one or more of the PO's have fiddled with the wiring some and left you with issues.