I've read enough that computer SMPS transformers can be used in reverse, or most transformers for that matter.
I'm feed in mine with 40v squarewave and 4 amps. I'm only getting a buzz from my meter(switching noise at 150kHz) but it reads 0.
Help me troubleshoot this.

 

So you have enough high power test equipment to drive a salvaged SMPS transformer with 40v 4A at 150kHz, but you don't have a scope?

Which pins are you driving? How have your measured anything, ie V or I going in or out of the windings? Any schematics or photos?

 

Normal digital meter. I measured current peaks at low frequency gating at 3 hz. Scopes are difficult to get.
See the schematic attached. I only made a change to the tx circuit by adding the RC series network to my perceived primary.
I've halved the frequency on the actual circuit. I'm yet to test the RLC network. I fail to get its purpose as regards to this circuit: I assume that it is used to absorb kickbacks...? In theory, based on these accounts, a snubber is really a non-necessity. Either way wouldn't hurt to put it.

second pin from GND bundle for the high power tx (the biggest of the three tx-es)
cheers.

 

I picked up a cheap second hand scope on ebay for £60.
The second channel has a fault but at least it gives me some idea of what is going on.

 

Sorry, but your diagram looks like complete rubbish.

Do you have any experience with SMPS supplies, or any high-freq test gear?

The SMPS transformer is very simple, you put HF AC current into one winding and it will produce HF AC current in another winding.