I recently purchased a used MBNM 550 EL measurement microphone on eBay for $99.95. The mic arrived and I plugged it in yesterday to compare with my other measurement mics. Zero output. Dead On Arrival.
Many times with eBay sellers, it’s like pulling teeth to deal with a situation like this but I was pleasantly surprised to receive this response back from the seller:
“Sorry about that, please keep the item and recycle it or use for parts, I’m sending you a refund now”