I removed the Tone Amp board from my Marantz 2238 Receiver to clean the pots and switches. This went well, I put it all back together, switched it on and it sounded fine. But after running for an hour smoke started pouring out of the transformer (not just a puff of smoke - a LOT of smoke) and the amp stopped. The transformer was too hot to touch and took hours to cool down. Could anyone suggest why this happened ? There wasn't any obvious evidence of a short anywhere. I'm worried I have killed my Marantz 🙁